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1. J2SE 5 0 Moni Connection f Summary Memory Threads Classes MBeans VM MBeans Attributes Operations gt v DefaultDomain re re Name Value oie i 5 gt D JMimplementation gt java lang gt java util logging Figure E 2 Monitoring the app Go to the MBeans tab Underneath the DefaultDomain item find the HitBean class you created for your app You should see the hits attribute filled in with the number of times you viewed the web page as in Fig ure E 2 Take a few minutes to play around with the interface Reload the web page a few times and then click Refresh in JConsole to update the attribute Switch over to the Operations tab and clear the hit count Of course JConsole is far from the only JMX client that would work with this web app In fact the same jmx gem supports writing your own client in Ruby Let s take a look at this technique Custom Clients We could monitor our web app from a separate Ruby program Download jmx web_watcher rb require rubygems require jmx client JMX connect port gt 9999 counter client DefaultDomain type HitBean this copy is P1 0 printing Jal WRAPPING OD Ya loop do puts The hit counter is at counter hits value puts Type R to reset or press Enter to continue counter clear if gets strip upcase R end As you can see we re reading the hits attribute and calling the clear me
2. Databases on page 133 and Chapter 7 Building Software for Deploy ment on page 165 will cover several Java and Ruby libraries in these areas In Chapter 8 Testing Your Code with JRuby on page 199 and Chap ter 9 Beyond Unit Tests on page 218 you ll find out how to use Java tools to run Ruby tests and how to use Ruby frameworks to exercise Java code You ll finish off the main part of the book in Chapter 10 Building GUIs with Swing on page 240 where you ll find what many Rubyists have long sought a cross platform GUI toolkit Who This Book Is For This book is for people looking to bring the Ruby and Java worlds together Some of you are seasoned Java developers who are interested in seeing what the Ruby language can do for you Others are familiar with Ruby and wondering what they need to know about running their code on the Java platform If your primary language has been Java up until now you may want to start with the quick crash course on Ruby syntax in Appendix A on page 272 If you re a Rubyist who s new to Java a book like Core Java HCO7 can help fill in the gaps without bogging you down in how to program lessons Online Resources We encourage you to try the code samples you see in this book by typing them in by hand If you get stuck or need a little more context the source for the examples is available at http pragprog com titles jruby source_code We designed these programs to run on JRuby v
3. S script The S flag is for running shell scripts using JRuby It comes in handy if you need to run a script that s in your PATH but isn t marked as exe cutable It s also useful if you have multiple scripts with the same name When you use this flag JRuby searches for your program in the follow ing places e The current directory e The JRuby bin directory SJRUBY_HOME bin e The directories in the PATH environment variable in order The S flag is especially helpful if you have multiple Ruby or JRuby instances on the system With it you can specify that you want to run JRuby s version of say the gem command rather than your system Ruby s version e command As an alternative to specifying a script file you can use the e flag to pass a snippet of actual Ruby code on the command line You ve prob ably seen this flag in action already and we use it liberally throughout this chapter Once you ve gotten used to having e around you ll won der how you ever got along without it directory Ruby searches for files to require or load on the load path provided in the or SLOAD_PATH global variable The I flag adds the specified directory or directories separated by your platform s path separator character to the load path so they will be searched as well r script The r option directs JRuby to load the specified file at launch time just as though your Ruby program loaded it with the require
4. The rest of your view code will go here end Now in src main rb search for the line that says Your application code goes here Replace that line with the following Download guis monkeybars sr main rb BookieController instance open The program needs to know where to find the definition of BookieCon troller By convention Monkeybars apps keep this information in src manifest ro Open this file and add the following lines to the end Download guis monkeybars src manifest rb add_to_load_path src bookie require bookie_controller That s all you need to run the app Click the Run button in the toolbar If NetBeans asks you to select a main class choose org rubyforge rawr Main You should see something resembling the other two versions of this app you ve written If you get an error message retrace your earlier steps to make sure all the variables and properties are set correctly Everything up and running Great Let s get to the code Report erratum P1 0 printing January 2011 MONKEYBARS lt 256 Model View and Controller As we mentioned Monkeybars is an MVC framework Over the next few pages we ll look at each of these components in turn Model Let s look at the model first since it contains no dependencies on Mon keybars It s just a Plain Ol Ruby Object PORO Replace the contents of src bookie bookie_model ro with the following Download guis monkeybars src bookie booki
5. That s a fair number of pointy angle brackets just to print out some text At least the intent is fairly clear When you run ant inside the directory containing build xml you get the following Download rake sessions ant_hello txt ant Buildfile build xml hello echo Hello Ant BUILD SUCCESSFUL Total time 0 seconds Great Now you have quick repeatable cross platform builds Ant adop tion benefits greatly from a shallow learning curve and spreads and multiplies from readily available copy and paste examples However veterans of Ant build scripts know from experience that they can quickly grow to become unwieldy beyond a few hundred lines of script Today JRuby s own build xml clocks in at almost 1 500 lines Of course code readability suffers in any code project once your files grow too large With Ant the problem is compounded because it s not a true programming language It lacks flow control and abstraction mech anisms so scripts get verbose and full of duplication more easily Just because doing our builds in XML suddenly doesn t feel so com fortable should we abandon Ant outright Certainly not The best part of Ant is its huge library of reusable tasks Why not put those to use in Ruby code as well With JRuby s Ant integration you can run Ant tasks from inside your Rakefile or indeed any Ruby file Ruby Colored Ants To begin using the Ant integration library just require it require ant
6. review reviewer name gt lt p gt lt p gt lt review content gt lt p gt lt h2 gt Comments lt h2 gt lt review comments each do comment gt lt p gt lt b gt By lt b gt lt comment said_by gt lt br gt lt Comment content gt lt p gt lt end gt lt h2 gt Add comment lt h2 gt lt render partial gt shared comment locals gt target gt review gt And there you have it a working application Of course you re proba bly tempted to add some visual styling nice navigational features and so on We highly encourage you to do so Have fun and drop us a line in the forums to show us what you ve come up with rt erratum this copy is P1 0 printing Jan or Shohei Tar WRAPPING UP lt 132 5 6 Wrapping Up In this chapter we introduced the Rails framework and built a simple Rails application on JRuby We also discussed a few differences from regular Ruby on Rails For the most part there hasn t been much of a distinction other than a couple of configuration settings Over the next couple of chapters we ll see where JRuby on Rails really shines database access and deployment options 6 1 Chapter 6 These days any upstart programming language has to have some kind of persistent storage support to be taken seriously Ruby is no excep tion in fact developers tout its fluid database connectivity Many of the techniques for connecting Rub
7. Comment content gt lt p gt lt end gt lt h2 gt Add comment lt h2 gt lt render partial gt shared comment locals gt target gt restaurant gt There are several things going on in this view First we display infor mation about the restaurant itself Below that we link to reviews and comments people have posted At the bottom of the page is a form for adding new comments That form will be shared between restaurants and reviews so we re keeping it in a separate file and using Rails s ren der method to reference it We ve followed Rails conventions and named the file shared _comment html erb this copy is P1 0 printin OPEN TO THE PUBLIC d 125 Download introduction_to_rails rouge app views shared _comment html erb lt form_for comment url gt action gt comment_on_ target id gt params id do f gt lt if comment errors any gt lt div id error_explanation gt lt h2 gt lt pluralize comment errors count error gt prohibited this comment from being saved lt h2 gt lt ul gt lt comment errors full_messages each do msg gt lt li gt lt msg gt lt 1i gt lt end gt lt ul gt lt div gt lt end gt lt p gt lt b gt By lt b gt lt br gt lt f text_field said_by gt lt p gt lt p gt lt b gt Content lt b gt lt br gt lt f text_area content gt lt p gt lt p gt lt
8. Imagine that this step required the doc directory to be in place before javadoc would run It doesn t but bear with us here By wrapping this code up in a Rake task and making it dependent on a directory task you can ensure that the directory structure will be in place when you need it Download rake baseball rakelib doc rake directory doc desc Build the documentation task javadoc gt doc do sh javadoc d doc java end Rake is smart enough to create just the directories you need If you have a directory task with foo bar baz and some other task requires only foo bar then Rake will skip creating baz Rules Now let s add a second Java class to the mix Here s the Java code Download rake baseball Catcher java public class Catcher Describes what kind of pitch the link Pitcher tossed public static void main String args Pitcher pitcher new Pitcher System out println The pitcher threw a pitcher pitchQ and here s the Rake task file Catcher class gt Catcher java do sh javac Catcher java end Notice how similar this is to the task for Pitcher How can we trim out some of this repetition By using another Rake feature the rule task Think of it as a template for file tasks this copy is P1 0 printing Download rake baseball rakelib compile rake rule class gt java do t sh javac t source end Descriptions and Access
9. Like the same Perl parameter that inspired it x tells JRuby to ignore the beginning of the file containing your program until it hits a ruby shebang line You can use it to run a Ruby program thats embedded inside a larger non Ruby file such as an email message Interacting With the JVM Now we ll move from the Ruby language to the Java platform as we consider options that affect how the JVM runs jdb If you re coming to JRuby from a Java background you may have used the command line jdb debugger to investigate problems with your pro grams or third party code When you supply the jdb argument JRuby runs with jdb instead of just java This allows you to set breakpoints and step through code We recommend you pair this option with the 3 http martiansoftware com nailgun index html Report erratum COMMAND LINE OPTIONS lt d 300 X C flag which we ll get to in a moment so that you can step through compiled Ruby code instead of being stuck in JRuby s interpreter sample JRuby ships with its own profiler which you can enable by passing the sample option As an example of how it can come in handy consider the Ackerizer example from Chapter 2 Driving Java from Ruby on page 31 You ll recall that we replaced a Ruby method with a Java one and saw a big speed increase This program was simple enough to be able to see by inspection where the slow code was In real world projects the answers are never
10. The Pragmatic grammers Using JRuby Bringing Ruby to Java 9 gt 4 i Charles O Nutter Nick Sieger Thomas Enebo Ola Bini and Ian Dees Forewords by Yukihiro Matsumoto and Bruce Tate Edited by Jacquelyn Carter teres SAMIR or Ruby Series What Readers Are Saying About Using JRuby I was very happy to discover the JRuby project my favorite program ming language running on what s probably the best virtual machine in the world This book really covers every in and out of this fantastic project gt Peter Lind Technical consultant Valtech I was floored by the amount of technical detail the authors managed to cram in here And they did it with such an approachable and read able tone that this book was both easy and fun to read I can t remem ber the last technical book that did that for me The breadth of cover age is astounding too gt Kent R Spillner My JRuby apps will go live in two weeks Without your book and the Ruby community I would never have gotten this far gt Pinit Asavanuchit Intersol Consulting Co Ltd I really liked the clear structure of the book and all the covered libraries dependencies like Rake Ant Maven testing frameworks This clearly outlines the whole JRuby universe so that new users will immediately see what s available and how to start using it gt Vladimir Sizikov Senior engineer Oracle This book will open the eyes of any Java programmer
11. When you rerun the program and click the button the result should appear immediately Now that we ve seen examples of the most common ways people use JRuby let s look at each step of the process in more detail 2 2 Dealing with the Classpath Before you can use that piece of external library wizardry you have to find it When you bring Java code into your app you re playing by Java s rules Rubyists are used to saying require some_file_name and counting on the file to show up inside one of Ruby s search paths By contrast Java looks for each class by its fully specified package name the physical location of the file isn t as important For readers coming from the Ruby world the classpath is the list of directories and jar files where Java and therefore JRuby will look for external libraries If you re doing a java_import see Section 2 3 By Importing on page 42 and JRuby can t find the class you re asking for the classpath is usually the first place to make adjustments A lot of people code in an IDE that sets up their classpath for them and deploy to a server that has its own notions of where things should be they ll never touch the classpath themselves But if you re using the command line a lot on your own you ll need to set the path up yourself JRuby supports several ways of doing this to ensure that both Ruby developers and Java developers will find familiar ground From the Command Line There
12. ant ant_import task goodbye_from_rake gt hello_from_ant do puts Goodbye from Rake end Importing Rake Tasks into Ant How about going the other direction making Ant aware of the names and dependencies of your Rake tasks Piece of cake Just as Rake has ant_import JRuby makes a rakeimport task available to Ant Assuming your Rakefile contains a task called hello_from_rake here s how you d call it from Ant lt xml version 1 0 gt lt project name hello default hello gt lt taskdef name rakeimport classname org jruby ant RakeImport gt lt rakeimport gt lt target name goodbye_from_ant depends hello_from_rake gt lt echo message Goodbye from Ant gt lt target gt lt project gt Now that we ve discussed the most popular Ruby build system the most popular Java build system and how they can work together it s time to move to other tools Report erratum this copy is P1 0 printing Jan 7 3 Maven Maven the popular build dependency and release management tool for Java projects has become a staple in the Java development land scape Maven is used to build many open source Java projects and Maven repositories are often the de facto place to download and man age library dependencies Let s look at a few ways that we can interact with Maven with JRuby Extending Maven with Rake Maven is well known to be opinionated and unwieldy if you need your build proc
13. gt ArgumentError something my_array gt Yay This feature is called splatting after the asterisk s nickname It s very handy so you ll see it used all over the place this copy is P1 0 printing A CLOSER LOOK lt 281 Common Ruby Types Just as you would expect the Ruby language and core library include a large number of built in types We re just going to take a look at the core data types that you ll need to understand to get going with Ruby Numbers Ruby uses three main classes to represent numbers Float Fixnum and Bignum As you ve no doubt guessed from its name Float is for standard IEEE floating point numbers The other two are for integer types fixed size for example 32 bit and arbitrarily large respectively Ruby will automatically use the right size type for each integer value Strings Matz took a great deal of inspiration from Perl when he created Ruby In particular Ruby shares Perl s excellent text manipulation abilities Many of these powers are vested in the String class Have a peek at the official documentation for this class and you ll see a lot of operations with useful self explanatory names reverse capitalize and so on You can create a Ruby string using several different literal syntaxes one hello world two is this right three This is a Ruby string isn t it he asked four lt lt ARBITRARY_END_ MARKER Here you can use layout whi
14. 2 1 Chapter 2 Driving Java from R It might be tempting to think of Java Ruby integration as nothing more than calling from one language to another But that s selling JRuby short In a typical project you re really interacting with both platforms You might construct a Ruby object pass it to a Java function and watch the Java code call other Ruby methods you ve defined In this chapter we ll look at cases where the interaction starts in Ruby calling Java methods from Ruby code implementing Java interfaces in Ruby and so on In the next chapter we ll start with a Java program and work our way back to Ruby Seeing Java Through Ruby Glasses The first use case for JRuby and still the most common one today is calling a Java method from Ruby Why would someone want to do this There are thousands of reasons Here are just a few of the things you can do with this interoperability e Visualize geographic data with NASA s World Wind project In Fig ure 2 1 on the following page you can see a map of our home towns that we put together with just a few lines of Ruby e Render beautiful SVG graphics with the Apache Batik project like the folks at Atomic Object did for their cross platform simulation app The elegant visuals they achieved are shown in Figure 2 2 on page 33 Image used with permission of the Avraham Y Gol dratt Institute LP 1 http worldwind arc nasa gov 2 http spin atomicobject com 2009 01
15. As we ve seen you can use the desc function just before defining a Rake task to give a description of that task Download rake baseball rakelib jar rake desc Build the application into a jar file task jar gt Pitcher class Catcher class Manifest do sh jar cfm baseball jar Manifest Pitcher class Catcher class end This serves a couple of different purposes It documents the Ruby code as a comment would but it also gives Rake something to report when you use the T option to ask for a list of available tasks If you skip the desc tag and define a task with no description Rake leaves it out of the T listing altogether This comes in handy for dis tinguishing public tasks which you invoke directly from the command line from private tasks which are used only by other tasks For exam ple the Manifest file is needed only by the jar task shown previously it makes sense to leave the Manifest task private Download rake baseball rakelib manifest rake file Manifest do File open Manifest w do f f puts Main Class Catcher end end Just because your private tasks are left out of the T report doesn t mean you can t run them Rake gives you the tools to stay organized but doesn t force organization on you Multitasking Right now our Java project has two main build targets jar for the program and javadoc for the documentation Lets put in a top level default task to tie these togethe
16. This new code tells Rails to route requests for http localhost 3000 and http localhost 3000 guide to the GuideController class This controller doesn t exist yet so let s generate it now jruby script rails generate controller guide OPEN TO THE PUBLIC If you start up the server again and visit http localhost 3000 you will notice that the regular Rails welcome page is no longer there Instead you ll get an error page because we haven t defined any GuideController actions yet We want the main page to display a list of restaurants that the user can choose from Edit app controllers guide_controller ro to look like this Download introduction_to_rails edits guide_controller1 rb class GuideController lt ApplicationController def index restaurants Restaurant all end end We also need to create the view for this action by editing app views guide index html erb Download introduction_to_rails rouge app views guide index html erb lt hl gt Welcome to Rouge lt h1 gt lt table gt lt tr gt lt th align left gt Name lt th gt lt tr gt lt restaurants each do restaurant gt lt tr gt lt td gt lt link_to restaurant name action gt show id gt restaurant gt lt td gt lt tr gt lt end gt lt table gt If you reload the page you should see a simple list of all the restaurants you ve added so far Clicking a link won t take you to a restaurant s page thoug
17. cd jruby If you want to compile the source of a specific release such as JRuby 1 5 5 run the git checkout command 9 git checkout 1 5 5 Finally build the software ant clean ant ant test Assuming the tests pass you re ready to run JRuby It s perfectly valid to specify a full path to jruby or jruby exe every time you run it JRuby will automatically figure out where its support libraries are relative to the executable But from here on out the examples in this book will be written as if you ve put the bin directory directly in your PATH as described earlier 1 2 Kicking the Tires Ready to try it First make sure you have a good executable jruby version jruby 1 5 5 ruby 1 8 7 patchlevel 249 2010 11 10 4bd4200 Java HotSpot TM If you have any problems getting to this point check your PATH and make sure you re running the latest release version of JRuby 7 http ant apache org 8 http www git scm com 9 To get out of building a specific release type git checkout master Report erratum this copy is P1 0 printing Jar THE INTERACTIVE SHELL It s time to run some code The simplest way to try a simple Ruby excerpt whether you re using plain Ruby or JRuby is to pass the e option to the interpreter jruby e puts This is a short program This is a short program Now that you re up and running let s look at some more useful ways to execute JRuby 1 3 The Intera
18. p name puts Hello name At some point that brilliant input output program you re writing is going to outgrow a single file Say you ve decided to put the main pro gram in main ro and some helper functions in helper ro In main rb you can just say require helper no trailing ro extension or load helper rb with extension The difference between these two is that require will only load a file once load will reload a file as many times as you call it And there you have it a whirlwind tour of Ruby in less than twenty pages Report erratum B 1 Appendix B JRuby takes great pains to do what you mean when youre passing data between Ruby and Java The situations we saw in Chapter 2 Driv ing Java from Ruby on page 31 should get you through most of your everyday use of JRuby For those times when you need fine grained control over how JRuby is copying your data or which overload you re calling you can refer to the details in this appendix How Method Selection Works JRuby tries to choose the Java methods and parameters that best fit what you re passing in from Ruby The upside is that things just work when your re calling Java from Ruby The downside is that describing how this process works requires a bit of detail Most of the time you won t need to worry about what JRuby is doing under the covers But in case you re curious There are two forces at play for method selection e Selecting
19. reviews gt 0 0060s gt 1 rows CreateReviews migrated 0 00605 s s ssSs s ses CreateComments migrating s s sS S sSSSS sSS S create_table comments gt 0 0060s gt 1 rows CreateComments gt migrated 0 00 0s Ssss lt s s sssseeseSaseeesss The models are looking pretty good on their own So let s make some associations between them We do this by modifying the various files in app models Adding Associations Let s begin with the Restaurant model Each restaurant will need both reviews and comments Here s how to express that relationship Download introduction_to_rails edits restaurant2 rb class Restaurant lt ActiveRecord Base validates_presence_of name has_many reviews has_many comments as gt commentable end this copy is P1 0 printir BUILDING OUR MODELS lt d 117 The first line we added reads almost like English A restaurant has many reviews The next line needs a little extra wording since a com ment can be associated with either a review or a restaurant The Administrator model is so easy that we don t need to make any changes at all to what Rails generated for us So lets move on to the Reviewer model Download introduction_to_rails rouge app models reviewer rb class Reviewer lt ActiveRecord Base has_many reviews end Now on to the Review model You ve probabl
20. s standard libraries have dependencies on the GUI graphics subsystem and the JVM helpfully starts up a GUI win dow for you when these libraries are loaded The headless flag and the java awt headless it sets to true behind the scenes suppresses this behavior so you can use those libraries without a GUI launching This flag is sometimes necessary on remote systems that do not have a win dowing system installed since they ll exit with errors if a GUI tries to start up Xoptions JRuby provides a few extended options for advanced users accessible by the X flag Passing the X flag alone shows the available options Specifying X C turns off JRuby s compiler so that all code is inter preted The opposite case is X C which attempts to compile every piece Report erratum 1 0 printing January 2011 COMMAND LINE OPTIONS lt d 303 of code as it loads and avoid the interpreter altogether The default com pile mode is just in time which only compiles frequently called code The X O flag enables per object tracking which is used by Ruby s ObjectSpace each_object method The default which you can explic itly specify with X O is to disable object tracking in order to save the associated memory and CPU cost Data Processing Now we re getting into some of the comparatively rare options Don t spend too much time learning these by heart just know you can flip to this section of the book if you encounter
21. this copy is P1 0 printing Jar A CLOSER LOOK def bio details for key value in details puts My key is value end end bio name gt Nick location gt Minneapolis drink gt tea rquest gt JRuby Prints My name is Nick My location is Minneapolis My drink is tea My quest is JRuby The loop in this example leads us naturally to our next topic program flow Control Structures You ve already seen a few simple examples of Ruby s if expression In its more complicated incarnation an if can be followed by any number of elsif clauses and optionally one final else Ruby also has unless which is the opposite of if For clarity s sake please don t use elsif or else with unless Most Ruby programs don t use lots of elsif conditions Once you are beyond a couple of conditions you ll usually want to get the extra flex ibility of Ruby s case def tel1l_me_about value case value when 0 9 puts It s a one digit number when Fixnum puts It s an integer when A Z 2 puts It s two capital letters when String puts It s a string else puts Don t know what it is end end this copy is P1 0 lt q 286 A CLOSER LOOK lt 287 A case expression checks its argument against each of the when clauses in the order they re listed As you can see you can compare Ruby objects by numeric range regular expression match class name and more Ru
22. we placed the Ruby source for the Waveform class into a file called waveform_with_sigs ro instead of just waveform rb If you look inside Waveform java you ll see something similar to the JRuby Embed example we cooked up earlier A simple Java wrapper class contains the full Ruby source embedded as a string plus a few methods that hand off their implementation to the Ruby class This approach has the advantage of being self contained a single java file is all you need to throw at your build system But there may be times when you don t want your Ruby source pasted into your Java class For these situations add the text java_require plus the Ruby file name minus extension anywhere in your rb file For this example you might put something like this right before the start of the Waveform class definition Download compiler waveform waveform_with_sigs rb require java java_require waveform_with_sigs Now when you recompile the generated Java code will have method signatures easier to call from Java public Waveform double points GE susie public double rms TT wea Report erratum THE DETAILS Remember that the jrubyc java command first generates a Java source file and then compiles that to bytecode JRuby just copies the class name as a string from your Ruby file into the generated text In other words this requirement is just a side effect of the way JRuby generates source code And there
23. JRuby options 299 302 Java testing see Ruby driving Java java lang Runtime 30 java lang System 30 java_alias 52 java import 42 43 91 java_method 52 java_package 92 java_send 52 javax scripting 7 1 JConsole 319 320 jdb debugger 299 JDBC METHODS JDBC drivers for ActiveRecord 136 integration with JRuby 161 163 jiro shell 24 JIT compilation see JRuby compiler JMX Java Management Extensions library 302 316 321 JNDI Java Naming and Directory Interface 138 JRuby application deployment 183 190 building from source 23 calling C functions 309 314 client vs server mode 302 command line options 24 26 294 306 debugging options 298 299 308 embedding in Java projects 60 76 filename case sensitivity 90 IDE recommendations 26 28 installing 21 23 integration with Ant 174 177 integration with Maven 180 183 interactive shell 24 interpreter functions 79 invoking command line tools 25 JVM related options 299 302 latest build 22 number of runtimes 195 profiling 300 301 properties 306 308 on Rails 103 131 Ruby version compatibility modes 73 295 307 testing Java code 200 202 229 239 thread support 171 using Nailgun server 298 299 see also JRuby compiler Ruby driving Java Ruby from Java JRuby compiler adding annotations 93 ahead of time AOT compilation 81 84 91 compiling directories of files 94 compiling to class file 28 85 compiling to Java bytecode 88 91 emb
24. Testcase test_value_is_associated_with_added_key HashMapTestCase BUILD SUCCESSFUL Total time 10 seconds From here we leave the tests in your capable hands 9 4 Wrapping Up This chapter began by showing how to use Ruby frameworks for higher level testing of Java programs We saw a tiny sampling of the web UI automation libraries available for acceptance testing Finally we talked about how to bring your elegant Ruby based tests into the world of sophisticated Java tools Don t wait to introduce great testing to your Java project Download JtestR today and tie it into your existing Java tests As you add new tests add them in Ruby using one of the expressive frameworks we ve seen If you re feeling really ambitious you might finish off by plug ging everything into a continuous integration server We think you ll find that Ruby is the best language for testing Java code no matter whether you prefer JtestR an ad hoc collection of libraries or some new and awesome tool that you re about to write and unleash on the world Now get testing 6 http wikijruby org JRubyAndContinuousintegration 10 1 Chapter 10 You ve heard it before write once run anywhere or WORA for short The term has been used and overused by Java developers over the past decade and a half to refer to the Holy Grail of portability Reality never quite lives up to the hype and indeed WORA s early waves of promise cras
25. before_filter authenticate Now add this near the bottom just before the end of the class declara tion Download introduction_to_rails rouge app controllers reviews_controller rb private def authenticate authenticate_or_request_with_http_basic Reviews do user_name password reviewer Reviewer find_by_username_and_password user_name password end end This code will make sure that reviewers are authenticated separately from administrators and will also store the logged in reviewer in the reviewer instance variable Our other controller actions can use that instance variable to decide whether to allow access For instance here s the new index method in ReviewsController Download introduction_to_rails rouge app controllers reviews_controller rb def index reviews Review find all conditions gt reviewer_id reviewer id respond_to do format format html index html erb format xml render xml gt reviews end end this copy is P1 0 printing Jan or Shohei Tan lt q 126 OPEN TO THE PUBLIC d 127 As you can see we re limiting our listing to show only the reviews asso ciated with the current reviewer We ll also want to restrict the show action which displays a single review s details Download introduction_to_rails rouge app controllers reviews_controller rb def show review Review find_by_id_and_reviewer_id params id reviewer raise Couldn t find Rev
26. gt I think this place is great gt gt chef Reviewer create name gt Swedish Chef description gt The Swedish Chef has dazzled audiences for years gt gt chef reviews create restaurant gt mac title gt A fine blend content gt Sometimes you find one of these exquisite experiences As you can see a few lines of ActiveRecord declarations have given us a nice internal API for our app Let s put that API to work now Restaurant Administration 101 We re going to add the web front end now starting with the adminis trative interface Once we have that in place we can use it to add data restaurants and reviewers for regular visitors to see Scaffolding Much as construction workers will set up scaffolds to support their work in progress Rails developers can take advantage of scaffolding code to support their newly created applications A Rails scaffold con sists of views and a controller for the standard CRUD operations Cre ate Read Update and Delete It gives you a basic web interface for your data which you can lean on as you gradually add your real busi ness code By the end of the project the scaffolding will have served its purpose and will be completely replaced We ll build scaffolds for three of our models Administrator Restaurant and Reviewer These are easy to create and they ll give us the chance to show off all four CRUD operations Let s start with the scaffold for the Admi
27. gt chapter_list dual_pane id gt dual_pane do tabs do tabs_shadow tabs_holder do tab_button text gt Edit sid gt edit_tab on_mouse_clicked gt scene dual_pane edit styles gt left_tab tab_button text gt Preview rid gt preview_tab on_mouse_clicked gt scene dual_pane preview rstyles gt right_tab end end preview_pane id gt preview_pane edit_pane players gt text_area id gt edit_pane end end add_chapter text gt Add Chapter end Download guis limelight bookie bookie styles rb default_border_color border_color b9b9b9 default_background_color background_color white fill_parent width 100 height 100 bookie extends fill_parent center horizontal_alignment center vertical_alignment center root extends default_background_color fill_parent text_color white font_size 18 APPENDIX F LIMELIGHT EXAMPLE SOURCE lt 324 center width 100 height 90 chapter_list width 10 height 100 bottom_margin 8 chapter extends default_border_color default_background_color center height 30 width 100 secondary_background_color fOf0Of0 gradient on bottom_border_width 1 right_border_width 1 dual_pane width 90 height 100 edit_button width 50 height 10 preview_button width 50 height 10 add_chapter extends default
28. value gt Catcher end end end end Working with Legacy Ant Builds Another situation where combined Rake Ant integration can help is by streamlining existing Ant based builds Suppose your Ant build has become too heavyweight and full of duplication Or perhaps you need to do some custom logic that is not manageable with Ant tasks In many cases throwing away your build xml is not feasible At times like these making a bridge between Rake and Ant can let each tool do what it s best at Report this copy is P1 0 printing Janua Importing Ant Tasks into Rake Ant from Rake didn t we just cover that Yes the ant method can blindly hand a task name off to Ant and say Run the task that has this name But the Ruby side isn t aware of the Ant tasks at all it s just throwing requests over the wall and waiting for answers So you couldn t make a Rake task depend on an Ant task using this technique If you re using Rake to package a gem that has a jar dependency for instance you wouldn t be able to have a gem Rake task that depends on a compile Ant task Fortunately there is a way to make Rake more Ant aware ant_import This method parses your build xml or any other filename you hand to it for top level Ant tasks and gives them names in the Ruby namespace that you can refer to for dependencies For instance if you have an Ant task called hello_from_ant you can use it in Rake like so require
29. ve seen in the previous chapter Ruby will have no problem calling methods on this Java object to extract the arguments Report erratum A REAL LIFE EXAMPLE SOURCE CONTROL First create a very simple Revisions Java class representing a pair of version identifiers Download ruby_from_java historian src book embed Revisions java package book embed public class Revisions private String start finish public Revisions String start String finish this start start this finish finish public String getStartQ return start public String getFinishO return finish Now add Ruby code to extract these fields and perform the diff We could build this code up in Java as one big string like we ve been doing In the name of brevity though let s put this glue code in a separate file lib archive4 ro which we ll later require Download ruby_from_java historian lib archive4 rb require git def history git Git open git diff revisions start revisions finish end The history function refers to a global variable Srevisions which holds a Revisions object from the Java side We ll soon see how that value gets passed in First though note that we re calling the Revisions object s getStart and getFinish methods using the shorter start and finish names We encoun tered this shortcut in Section 2 4 Instance Methods on page 44 it s nice to be able to use it to keep our
30. you can do something like this Download databases ribs_use rb dog R Book get 1 dog title How We Found the Bishop s Bird Stump at Last R dog save Report erratum Note that you can get an instance with a specific ID by calling get on the class repository You use regular Ruby accessors to change data and wrap the instance in a repository to save to the database The easiest way to create new instances is through the class reposi tory s create method Download databases ribs_use rb R Book create id gt 4 title gt Goedel Escher Bach author gt Douglas Hofstadter This method will first create a new instance of the class then set all the values you ve specified and finally save it to the database You don t have to use a repository to create instances though You can call new set up instance methods just like you d do for any other Ruby object and involve repositories only when you re ready to touch the database Download databases ribs_use rb snow Book new snow id 5 snow title Snow Crash snow author Neal Stephenson RCsnow save To remove a row from the database you use the destroy method This will delete the row and remove any mention of the object in the Hiber nate caches Download databases ribs_use rb R Csnow destroy These examples have all shown how you can work with Ribs in a sim ple case where everything just happens to be named according to
31. 2 b2 title My second blog revisited b2 posts create title gt First post tbody gt This is a post about something b2 save my_blogs Blog where author gt Ola Bini my_blogs first destroy This example shows only a small extent of what s possible to do with an ActiveRecord model but it shows enough to get you started Let s run through the interesting parts of this code snippet First a model object can be created using new exactly as any other Ruby object You can also give this call a hash of initial values for attributes Any attribute can be set by just using a setter ActiveRecord provides these for columns in the table such as title and for associated objects like posts Report erratum RUBY DATABASE FRAMEWORKS lt 146 To push a newly created object to the database just call save or savel The difference between them is that the first one returns false if it couldn t validate the object or save it to the database for some reason The bang version will throw an exception instead If you want to initialize an object and save it to the database in one step you can use create or create To retrieve an object from the database you use the find method with the blog s unique ID You ll notice we didn t supply any IDs when we created the blogs this is a detail that ActiveRecord prefers to take care of The next lines update some attributes and also put a new Post into the b
32. 30 ruby for desktop applications yes we can SEEING JAVA THROUGH RUBY GLASSES 4 32 AOO JRuby Authors a i oe EURGPE North Atlantic Ocean South Pacific Ocean South Atlantic Ocean SOUTH AMERICA 2 E 2000 Km Figure 2 1 Locating JRuby authors with World Wind e Handle a protocol or data format for which a Java library is the best fit For example you might choose the Java based iText li brary to add PDF support to your Ruby program especially if you need digital signatures or some other feature specific to iText e Slay the cross platform Ruby GUI dragon by writing a Swing or SWT program in Ruby e Boost the performance of a Ruby program For example the team behind the Redcar text editor knows they will always have the option of dropping down into Java for any performance critical parts a Report erratum this copy is P1 0 printing January 2011 Prepared exclusively for Shohei Ta a l Processing SEEING JAVA THROUGH RUBY GLASSES 0 x Simulation Schedule View Application Help 110 More Quality Problems option 1 Pence Schedule Buffer Finance Weeks 1 Weekly Expenses 11 000 Product A Product C Product E ETa n 350 10 200 a E Idle Processing B2 Ca b Hour 7 of 40 Day 1 of S Figure 2 2 Simulating industrial processes with Batik e Tame a legacy Java project by walling off the old spaghetti
33. 306 It s yet another powerful tool for command line data processing Use it wisely C 2 Properties JRuby like many other JVM based languages and libraries also in cludes some properties that let you access internal or experimental settings Although we don t have room to discuss every possible prop erty there are a few particular ones you may find useful You can get the full list using jruby properties Tweaking the Compiler The first set of controls is for fine tuning JRuby s just in time compiler jruby compile mode JIT FORCE OFF Normally JRuby runs in JIT mode meaning that it compiles frequently executed functions to JVM bytecode You can force JRuby to compile all Ruby files at load time using FORCE which is the same as running with X C If you want to run everything interpreted and generate no bytecode which you might want to do for restricted environments like applets or mobile devices you can specify OFF which is the same as X C jruby jit threshold invocation count As of JRuby 1 5 the default number of calls before a method will JIT is 50 If you want to make it happen sooner or delay compiling methods for more invocations adjust this property appropriately jruby jit max method count This sets the maximum number of Ruby methods to JIT compile which by default is 4096 per JRuby instance Specifying O disables all JITing and specifying 1 means no maximum count jruby jit logging true fa
34. 70 3 3 Embedding Strategies soos rrara sasiad 74 94 Wrapping UD s tac ee ci s aii eah ee a e 77 4 The JRuby Compiler 78 4 1 Compiler IQ 6 360585 256584244086 8 78 4 2 A Simple Compiled Example 85 4 3 The Details e soe soso oee eati ee ee we ee eS 91 44 Wrapping UD o lt o ec eek ea awe ORES BO 96 I JRuby and the World 97 5 Introduction to Rails 98 5 1 Whatis Rails e s epre we die we a sodi e das ie 98 5 2 Going Roug 23 5 5 668s eee Be eR tket 105 5 8 Building Our Models 2 42458 2448 64545 111 5 4 Restaurant Administration 101 118 5 5 Open tothe Public oios ese chee eee wes 122 56 Wrapping Up accio 44 64 s4 452 eee ee RS 132 6 JRuby and Relational Databases 133 6 1 Ruby Database Frameworks 133 G2 WIDS 6 bk paoe ok ee ke ee ee ES 154 6 3 SDBO easy nirede wp 6054 E44 e 4 48 161 GA Wrapping Up 64244446 bode eh ade wake 164 7 Building Software for Deployment 165 Gls RAG eo ed eb a BA oe Wale eG ee Be Ss 165 Ta ADE ys hoe oo a ga a doe oe we ee es 173 Gee MNs hi oth is be ee ee Oe GS eS BES amp aw 180 7 4 Packaging for Deployment 183 To Wrapping UP ssi Sn Gok kee a Eoee a a 198 Report erratum is P1 0 printing January CONTENTS 8 Testing Your Code with JRuby 199 8 1 Ruby Test Frameworks 200 8 2 Going to the Next Level with ZenTest 212 8 3 Mocking and Stubbing 212 SA Wrapping UPD ee aea we ee
35. First there is the props rb file Download guis limelight bookie bookie props rb root do center do chapter_list id gt chapter_list dual_pane id gt dual_pane do tabs do tabs_shadow tabs_holder do tab_button text gt Edit tid gt edit_tab on_mouse_clicked gt scene dual_pane edit styles gt left_tab tab_button text gt Preview tid gt preview_tab on_mouse_clicked gt scene dual_pane preview rstyles gt right_tab end end preview_pane id gt preview_pane edit_pane players gt text_area id gt edit_pane end end add_chapter text gt Add Chapter end This file spells out the GUI controls in the app The structure of the code mirrors the nested relationships among all the props in the scene Props can have attributes either stock ones that come with Limelight such as on_mouse_clicked or custom ones we define such as id You ll notice there s no information on size location or color How does Lime light know where and how to draw these It uses information from styles rb The style file is typically a scene s largest file It s also the one you ll spend most of your time in We re not going to do a line by line explica tion here Instead we ll just take a close look at the tab control this copy is P1 0 printing LIMELIGHT lt 265 tabs holder tab button tabs shadow Figure 10 5 Bookie in Limelight The following
36. JRuby We ve chosen not to inundate you with an uncurated alphabetical listing Too many options depend on one another for such an order to make any sense Instead we ve broken down the settings by category Command Line Options First let s look at arguments you pass to the jruby executable on the command line Getting Information About JRuby The first few options are the ones you d likely reach for first when learn ing your way around a new environment copyright and version These do what you d expect they display the copyright and version information for JRuby The version information also includes the exact Ruby language version on which your JRuby installation is based This can come in handy for reporting bugs in libraries properties This option prints out a huge list of settings that affect how JRuby finds loads interprets compiles and runs code A short description and default value accompany each property COMMAND LINE OPTIONS lt 295 If you re interested in tuning JRuby s performance under the hood keep reading this chapter for information on how to change these prop erties Make sure you pay attention to the ones marked as experimental or dangerous h or help We were wondering whether to even mention the help option Doesn t every program support this Still we re bringing it up because it really is a good idea for you to take a minute and explore some of the various options
37. JRuby offers you Running Ruby Code The options in this section control how JRuby executes Ruby code Most of these are also present in the C implementations of Ruby v verbose and w The v and verbose flags set the global variable SVERBOSE to true print JRuby s version information and then proceed to execute the provided script If no script is provided JRuby will only print its version This variable directs Ruby programs and the JRuby environment itself to enable extra logging Specifically the Kernel object s warn method pro duces output only if SVERBOSE is true The w is the same as v except the former does not print any version information when JRuby launches K code Ruby 1 8 and JRuby in 1 8 mode normally default to ASCII as the expected character encoding With K you can specify a different encod ing such as UTF 8 Acceptable encodings are UTF8 SJIS EUC or ASCII aka NORMAL The values are case insensitive and only the first char acter matters 1 8 and 1 9 JRuby currently starts up in Ruby 1 8 compatibility mode by default but you can force it to run in 1 9 mode by specifying the 1 9 flag In the future 1 9 mode may become the default at that point you ll use 1 8 to specify compatibility with Ruby 1 8 instead 1 As of this writing JRuby s support for UTF 8 and ASCII is more complete than for the other encodings Report erratum COMMAND LINE OPTIONS lt d 296
38. JRuby with your Java infrastruc ture You just download a jar file add a few lines to your Ant build file and then start writing tests Here s what you get when you install the latest version of JtestR 0 6 as of this writing e JRuby 1 5 e Test Unit e RSpec e Expectations another test framework e dust yet another test framework e Mocha e ActiveSupport We ve already been through most of these libraries So we ll just take you on a tour through JtestR s capabilities and show you how to get started with it Fast Startup One of the problems with using JRuby for testing is the long startup time You want your tests to run instantaneously so that nothing gets in the way of constant testing JtestR speeds up testing by providing Report erratum PLUGGING INTO JAVA a background server with a pool of ready to use runtimes When a client wants to run a test the server assigns it a runtime and prepares another one Build Tools Anything intended to be part of the Java ecosystem needs to have extremely good integration with the currently available tools JtestR ties in with the two most popular Java build tools Ant and Maven This integration requires only a simple one time setup Here s what an Ant build file would look like assuming you ve saved JtestR to lib jtestrjar Download beyond_unit_tests jtestr build xml lt xml version 1 0 encoding utf 8 gt lt project basedir default test name sim
39. Java idioms to the Ruby way Constructing Java objects falls right into this aesthetic you just use the normal Ruby new class method You might wonder how this is possible since Java sup ports overloaded methods including constructors and Ruby doesn t But JRuby sweeps this difference under the rug for you looking at the parameters you pass to new and selecting the constructor that best matches those arguments We ll see more detail on argument matching in a minute First let s look at a concrete example Java s URL class has several constructors including these two new URL String spec new URL String protocol String host String file JRuby will choose the best match when you call new Download java_from_ruby instances rb URL new http pragprog com titles URL new http pragprog com titles Instance Methods Just as with static methods JRuby maps instance methods to nice snake_case ones for you Download java_from_ruby instances rb url get_protocol gt http As an added bonus Java style getters and setters are callable as Ruby style attribute accessors In other words the following two lines are equivalent Download java_from_ruby attributes rb car setPrice 20_000 car price 20_000 this copy is P1 0 printing Jan 2 5 PASSING PARAMETERS Instance Fields On its own JRuby doesn t seek out a class s fields and try to map them to Ruby attributes After all most field
40. Successfully installed diff 1lcs 1 1 2 Successfully installed rspec expectations 2 0 1 Successfully installed rspec mocks 2 0 1 Successfully installed rspec 2 0 1 5 gems installed Report this copy is P1 0 printing Janua lt a 203 RUBY TEST FRAMEWORKS In the following snippet we describe an empty HashMap given to us by the setup code using specific statements about its behavior it should have size zero and so on Download testing_with_jruby rspec hashmap_spec rb require java java_import java util HashMap describe An empty HashMap do before each do map HashMap new end it should be empty do map should be_empty end it should have size zero do G map size should 0 end it should allow elements to be added end You can run the code like this jruby S rspec hashmap_spec rb Pending An empty Java JavaUtil HashMap should allow elements to be added Not Yet Implemented hashmap_spec rb 18 Finished in 0 046 seconds 3 examples O failures 1 pending As you can see the text passed to the describe method explains what goes on in the before each block In other words it gives the context of the examples One thing you ve no doubt noticed is that the third example has no implementation Presumably the next thing we re going to do is write that test In the meantime RSpec will report it as pending and will print its description to jog our memory with what we need to
41. System currentTimeMillis gt 1251075795138 But the Java convention of using camelCase looks out of place among Ruby s snake_case names Your code will look more Ruby like if you take advantage of JRuby s automatic mapping between Ruby names and Java names Download java_from_ruby static rb java_import java lang System System current_time_millis gt 1251075795172 The mapping also knows how to deal with function names containing capitalized abbreviations like URL Download java_from_ruby static rb java_import java net URL assume you ve initialized some object factory here URL setURLStreamHandlerFactory factory URL set_urlstream_handler_factory factory Static Fields Static fields of Java classes are typically used to implement either sin gleton objects such as Logger global or constants such as Level SEVERE For the former case you ll just treat the field like a Ruby class level method calling it with dot notation and a Ruby style snake_case name For the latter case you ll treat the field like a Ruby constant accessing it with double colon notation and matching the Java capitalization Report erratum USING OBJECTS Here s an example that shows both situations Download java_from_ruby static rb java_import java util logging Logger java_import java util logging Level Logger global log Level SEVERE It looks like you re writing a letter Object Construction JRuby adapts many
42. System out printIn p name performs c getName How do we call this method from JRuby There s no primitive Java type we can convert the parameter to It s expecting a full on Java class name with a runtime annotation attached Fortunately JRuby can cre ate a Java class for us on the fly based on our Ruby class Download java_from_ruby mischief rb require java require jruby core_ext java_import PerformedBy java_import Chronicler java_import Sorcery class Mischief more mischief here end Mischief add_class_annotation PerformedBy gt name gt Ian Mischief become_java this copy is P1 0 printing Jal IMPLEMENTING A JAVA INTERFACE Chronicler describe Sorcery gt gt gt Charlie performs Sorcery Chronicler describe Mischief gt gt gt Ian performs ruby Mischief The add_class_annotation method imported from JRuby s core_ext exten sions decorates the Ruby class with the necessary annotation By it self this doesn t mean much since the Ruby universe won t know to look for this information But when we use the become_java method to promote Mischief to a real Java class the Chronicler is able to see the PerformedBy annotation 2 7 Implementing a Java Interface What do you do when the function you re calling expects you to pass in a Java object implementing some specific interface Consider Execu tors callable which wraps a Runnable up ins
43. TO THE PUBLIC lt d 122 lt table width 50 gt lt tr gt lt td gt lt link_to Administrators administrators_path gt lt td gt lt td gt lt link_to Restaurants restaurants_path gt lt td gt lt td gt lt link_to Reviewers reviewers_path gt lt td gt lt tr gt lt table gt lt p style color green gt lt flash notice gt lt p gt lt yield gt lt body gt lt html gt All three of the authenticated controllers will share this common HTML structure If you reload any of the administration pages in your browser you should now be able to switch among them with the link bar 5 5 Open to the Public Now that we have an interface for the administrator it s time to turn our attention to the general visitor As a first step we need to remove public index html so we can have dynamic content on the front page Once that s done we need to change the routing Routes to Success The routing system is what Rails uses to decide which controller to call when a request arrives It maps URLs such as htip localhost show index to controller actions such as ShowController s index method It s quite a flexible system but for now we only need a tiny piece of its power Open config routes ro and add these two lines anywhere inside the main block Download introduction_to_rails rouge config routes rb root to gt guide index match guide action id gt guide
44. Xdock name My Program some_jruby_program rb If you launch your program with this extra flag the Dock icon will carry the name you specify instead of just org jruby Main Report erratum COMMAND LINE OPTIONS lt 302 server and client Even though the J gives you access to the full range of command line parameters for the JVM a few settings are common enough to warrant their own dedicated JRuby arguments Such is the case with server and client which launch the Java runtime in server or client mode for JVMs that support this choice Server mode optimizes for long running processes at the cost of longer startup times So don t go crazy and use it on every single JRuby pro gram you write But keep it in mind for things such as websites and message queues Client mode optimizes less but does so sooner and with less impact to startup time and cold performance JRuby usually will default to client mode except of course on JVMs that don t have a client mode like 64 bit Hotspot based JVMs manage All standard Java SE runtimes ship with support for the Java Man agement Extensions JMX which allow you to manage a running JVM remotely Many distributions of Java do not have remote JMX enabled by default so JRuby provides the manage flag to turn it on On Hot spot Sun s VM or OpenJDK this simply sets the Java property com sun management jmxremote headless Many of Java
45. basebal 1 Compiling 2 source files The javac task also knows not to recompile files whose source hasn t changed if we run the task again no work is done 1 http ant apache org manual Report erratum Download rake sessions ant_compile2 txt jruby S rake ant compile Cin code rake basebal1 Next let s take a look at how to generate documentation Ant also comes with a built in javadoc task Download rake baseball rakelib ant_doc rake namespace ant do task javadoc do ant javadoc sourcefiles gt FileList java destdir gt doc end end There are a couple points to be made about this example One thing you ll notice is that we re starting to use a little bit of Rake where it feels right In this case Ant s javadoc task takes a comma separated list of files in its sourcefiles attribute JRuby s Ant library treats FileLists spe cially by passing them to the underlying Ant task as comma separated values Finally to complete the Baseball build we need to create a jar file Here we can make use of Ant s jar task which allows you to specify manifest attributes inline so we don t need an extra task to create the manifest file like we did with plain Rake Download rake baseball rakelib ant_jar rake namespace ant do task jar gt compile do ant jar basedir gt destfile gt baseball jar includes gt class do manifest do attribute name gt Main Class
46. begin with the browser based approach because despite its complexity it s actually easier to get started with Selenium and Watir are two different tools that share the same pur pose taking control of a real web browser in order to help you test your application Selenium is language and browser independent By contrast Watir is Ruby only it s right there in the name Web Applica tion Testing in Ruby and was originally specific to Internet Explorer To target a different browser you install a flavor of Watir made for that browser FireWatir SafariWatir ChromeWatir and so on Both libraries have their uses and in fact either one would do fine for implementing the steps of the Cucumber test we saw earlier So we re going to look at both Selenium Selenium is available in a Ruby friendly format consisting of two gems the remote control server which does the dirty work of driving the browser and the Ruby client interface Here s how to install the gems and start the server Report erratum 0 printing Janu ACCEPTANCE TESTING lt 222 jruby S gem install selenium rc selenium client jruby S selenium rc Keep that server running in the background as you turn your attention to the more interesting part the step definitions These should go into step_definitions search_steps rb Download beyond_unit_tests selenium step_definitions search_steps rb Given AI am on the search home page do browser
47. code behind a clean Ruby interface e Sneak Ruby into a Java shop after all JRuby is just another jar file e Write great tests for your Java code using one of Ruby s outstand ing test frameworks e Index and search huge amounts of text with the Lucene search engine e Write a database backed web application in the Rails framework Behind the scenes Rails s database adapters call into Java s data base libraries to do the heavy SQL lifting or http lucene apache org this copy is P1 0 printing Jan SEEING JAVA THROUGH RUBY GLASSES All of these scenarios are the bread and butter of JRuby and are well supported But as in any domain where two languages meet there are some subtleties gotchas and impedance mismatches This chapter will address many of these edge cases First things first though We ll lead off with the basics of accessing Java classes from JRuby starting with how your Ruby code can load and interact with Java libraries Then we ll explore the details of param eter passing and automatic type conversions Finally we ll show a few tips and tricks to make Java classes and objects a natural part of your Ruby programs A Simple Example Wrapping a Library Let s start with a working program to drive a Java library We ll expand on one of the examples we described earlier using the iText library to generate a PDF file This will be just enough to give a hint of the flavor of dr
48. code clean here this copy is P1 0 printing A REAL LIFE EXAMPLE SOURCE CONTROL How does the assignment to the Srevisions variable happen Via the scripting container s put method Download ruby_from_java historian src book embed Historian4 java ScriptingContainer container new ScriptingContainer container setLoadPaths Arrays asList lib container runScriptlet require archive4 container putC revisions new Revisions args 0 args 1 System out printIn container runScriptlet history Notice that the ScriptingContainer object remembers what s happened to it from one invocation of runScriplet to another The call to history works because it remembered the previous require of archive This continuity is incredibly useful You can do expensive setup opera tions once at the beginning of a program and then later just consume those loaded Ruby features without having to reload them for every call to runScriptlet Go ahead and try the new Historian by passing in a couple of revision identifiers on the command line bin historian4 HEAD 2 HEAD diff git a lib archive7 rb b lib archive7 rb new file mode 100644 index 0000000 1d5967f dev null b lib archive7 rb 0 0 1 12 require git Our use of the embedding API is starting to look less like a throw it over the wall and cross your fingers approach and more like a real interaction between Java and Ruby We
49. connecting to Ribs is to define one or more databases One of these must be named the default For example Download databases ribs_connect rb require rubygems require ribs Ribs DB define db1 do db Basic connectivity db dialect MySQL db uri jdbc mysq1 localhost 3306 using_jruby user root amp password db driver com mysql jdbc Driver Extra options db default true db properties hibernate show_sq l true end 11 http www hibernate org 12 http github com olabini ribs Report this copy is P1 0 printing Janua Ola Says Since Ribs builds on the strong base of Hibernate decided early on to make a few things different from the way Ruby data base frameworks generally work with models Some of these decisions make the usage of Ribs look quite different Making Ruby objects persistent with Hibernate is one side of the coin One day l d like to add the flip side driving an existing Hibernate domain model written in Java with Ribs This would allow you to very easily use an existing Java model in your Rails application for example Other future possibilities include both a migrations framework and some way of handling validations There are a few things to notice here First in the manner of Hiber nate you specify a dialect a URI and a driver class You can add any kind of extra properties for Hibernate here too Here we re using Hiber nate s show_
50. count as false like values Rubyists sometimes colloquially refer to this loose definition of truth as truthiness in a nod to comedian Steven Colbert Just to hammer the point home consider the following exploration of truthiness in Ruby def truthy value if value then true else false end end truthy true gt true truthy false gt false truthy nil gt false So far so good Let s look at a few more surprising cases truthy 7 gt true truthy gt true truthy 0 gt true As you can see even empty strings empty arrays and the number zero are truthy in Ruby 2 http en wikipedia org wiki Truthiness A CLOSER LOOK lt 284 Operators and Assignment Most Ruby operators are just methods with weird names For example if an object has a method named then that object can participate in expressions like a b The only operators that aren t methods are those that are deeply woven into the syntax of Ruby such as the assignment operator a single equal sign You will recognize many of Java s operators in Ruby but there are a fair number that may be unfamiliar or at least slightly different from their Java equivalents They are as follows Operator Description These methods read and write values in collections lt gt This method affectionately called the spaceship operator compares values during searching and sorting much like the comparelo metho
51. default to an id column as the primary key Since Sequel came out ActiveRecord has gained similar lazy loading features Starting with version 3 ActiveRecord will put off as much work as it possibly can until you absolutely need to hit the database This allows both Sequel and ActiveRecord to optimize their queries and avoid creating an excessive number of Ruby objects http m onkey org 2010 1 22 active record query interface You can use square brackets to find a model based on conditions For example you could call Blog name gt Music to find any blog with the name Music Most of the familiar Sequel filtering operations work fine inside square brackets Sequel Model is quite a thin wrapper over reg ular Sequel so most of the concepts should be recognizable Sequel models allow you to specify associations between them much in the same way as ActiveRecord does This is very well documented on the Sequel website and it works exactly the same in JRuby as it does in regular Ruby All in all Sequel is a really nice database library It takes a very different approach than both DBI and ActiveRecord but this approach makes it a really advanced tool 6 2 Ribs Database libraries for Ruby generally share the same goal of making the most common cases achievable with very little code which is why we have the table naming conventions automatic primary keys and so on Sometimes however you have legac
52. don t need to define any mappings at all between SQL and Ruby With the table of books have sitting in the database we can define a Ruby class and start using it directly with Ribs Download databases ribs_use rb class Book attr_accessor id title author end p R Book all This code will create a class called Book and add three accessors for the book s properties Manually adding these isn t strictly necessary if Ribs doesn t find any accessors it just uses the values of instance variables directly instead There is no need to define a mapping from class fields to table columns here because we re using the same names for both Case doesn t matter at all in this example but in contrast to Sequel and ActiveRecord table names need to be singular for models to find them If you need to define custom behavior for a model you can do so completely outside the model class if you like there is no tight coupling between the database and the model The actual database call happens when we invoke the R method This gives us back a repository an object that can be used to find out differ ent information based on the model we passed in And that s how you work with Ribs you wrap a plain Ruby object in a call to R and then call methods on whatever you get back In this case the all method just returns everything from the database You can also filter out things by passing arguments to all To access and manipulate data
53. end end this copy is P1 0 p A fun way to compare the XML and Ruby versions of the build file is to open both in your text editor of choice and quickly cycle back and forth between the two files in a single window effectively animating the minor differences between the two If you re like me watching the angle brackets disappear rein forces the subtle power of omitting extra line noise That stream lining frees up your mind to be able to see the true intent of the program See how the nested pattern of the blocks matches the nested structure of XML elements but without all the angle brackets This technique is used in several Ruby libraries that manipulate XML such as Builder and Markaby Ruby blocks are a natural way to indicate grouping So we have a way to execute chains of Ant tasks but what about defin ing build targets We can do that too Here s the equivalent to the build xml example earlier Download rake ant hello build rb require ant ant name gt hello default gt hello do target name gt hello do echo message gt Hello Ant end end A nice feature of the Ant library is that if you run the file containing your Ant code as a script it becomes a full fledged Ant build Let s run our aptly named build rb Download rake sessions jruby_hello txt jruby build rb hello Hello Ant To run a specific target add it to the end of the command as an argu ment to the script If y
54. expressed with the intuitive include and exclude notation So there you have it a minimal Java project that has managed to touch on all the important features of Rake Now let s see how to integrate Rake more deeply with Java s build systems Ant No matter what specialized task you need to perform to build your Java project chances are that it s been done before with Ant Ant is the oldest most established Java build tool It was originally created during the open sourcing of the Tomcat Java web server and was later released as a stand alone project Ant solved a lot of make s portability problems by implementing commonly used build tasks in Java As Ant continued to mature it amassed a wide library of portable reusable functions tasks for every conceivable software development function These include checking out compiling testing and packag ing code downloading uploading and deploying build artifacts and more Of course Ant is also notorious for the fact that its build scripts are written using verbose XML With small to medium sized projects Ant XML seems fairly innocuous Let s consider the simplest possible Ant build file Download rake ant hello build xml lt xml version 1 0 gt lt project name hello default hello gt lt target name hello_from_ant gt lt echo message Hello from Ant gt lt target gt lt project gt Report erratum 1 0 printing January 20 1 1
55. for Ruby and Ant and Maven for Java relate to JRuby projects Rake Rake is Ruby s answer to the venerable UNIX make utility Jim Weirich began the project in 2003 as a special purpose language for describing software tasks and their dependencies Why a new build tool Consider a simple C style Makefile for sandwich making Download rake sandwich Makefile Make a tasty lunch sandwich bread cheese echo Grilling the sandwich I guess sliced bread really is the greatest thing bread echo Slicing the bread Only the finest Emmentaler for our sandwich cheese echo Grating the cheese The sandwich task depends on the bread and cheese tasks and so Make will ensure that they run first This method of building software has stood solidly at the base of software development for decades But it s not without its drawbacks Make is fussy about exact indentation tabs and spaces It suffers from subtle variations from vendor to vendor And for any advanced features such as making build decisions based on what platform you re using your re stuck The result has been a series of horrendous Makefile makers each with its own arcane syntax Now let s look at the same set of tasks expressed as a Rakefile Download rake sandwich Rakefile desc Make a tasty lunch task sandwich gt bread cheese do puts Grilling the sandwich end desc I guess sliced bread really is the greatest thing task bread do
56. great sup port for Ruby and all three of them stay out of our way while we re coding x http www gnu org software emacs t http vim org t http macromates com This approach works for any Ruby command line tool including gem rake spec and others There are a ton of other useful JRuby options for more information type jruby help or see Appendix C on page 294 1 5 IDEs JRuby is easy to use from the command line so much so that we ll be giving many examples of it in this book But using an integrated development environment has its merits In addition to the code com pletion features most people think of IDEs can manage your JRuby installation and classpath for you Nearly every popular IDE has some support for Ruby either directly or through a plug in If you re asking us for a recommendation though we have two RubyMine RubyMine is a Ruby specific IDE created by the JetBrains company It has the level of sophistication you d expect from the folks who created IntelliJ IDEA the beloved Java development environment 12 http wwwijetbrains com ruby index html Report erratum Development rouge restaurant_test rb def test_can_instantiate_and_save_a_restaurant ier restaurant Restaurant new E public restaurant name Mediterraneo Si script restaurant description lt lt DESC GP test 0ne of the best Italian restaurants in the Kings Cross a
57. install sinatra Add the following code to the end of the file you ve been working in Download jmx web_app rb require sinatra get do bean hit We re watching you end 4 http wwwssinatrarb com this copy is P1 0 printing Jal MONITORING APPLICATIONS 319 Host or IP localhost Port 9999 User Name Password Figure E 1 Logging into JConsole This will increment the hit counter every time someone visits the page The information will not be visible to users but will be available to administrators through JMX Go ahead and run the app Assuming you ve saved the code in web_app rb you just run it like any other JRuby program jruby web_app rb Go to hittp localhost 4567 in your web browser you should see the text We re watching you Hit Refresh a few times to bump up the internal hit count Remote Administration Now that our web app is serving up statistics via JMX we need a remote client to report the data It would be easy enough to write one in JRuby using the same jmx gem we ve been discussing But there s an even eas ier way the jconsole command that comes with Java When you launch it like this jconsole you should see a window like Figure E 1 On the Remote tab fill in localhost and 9999 for the host and port and then click Connect The main window should fill in with details about the web app MONITORING APPLICATIONS lt 320
58. int countTestCases return 1 public void run TestResult result ScriptingContainer runtime new ScriptingContainer runtime runScriptlet require test_unit_junit Object junit_class runtime runScriptlet JUnitAdapter Object junit_instance runtime callMethod junit_class new result runtime callMethod junit_instance run_tests public static Test suite return new TestUnitSuite this copy is P1 0 printing Jal PLUGGING INTO JAVA 234 This class s three methods provide the interface that JUnit expects to see The interesting bits are all in the run method Using the tech niques from Chapter 3 Ruby from Java Embedding JRuby on page 60 we load our Ruby code into a new ScriptingContainer object create an instance of a Ruby class and call its run_tests method To build this Java code you can add something like the following frag ment to your Ant build file Download beyond_unit_tests junit_integration build xml lt target name compile description Compile the source files for the project gt lt javac destdir debug true source 1 5 target 1 5 gt lt classpath refid build classpath gt lt src path gt lt javac gt lt target gt Provided that you have both jruby complete jar and junit 4 8 1 in your build classpath you should get a clean build with ant compile at this point The Ruby Adapter The Ruby code is a lot more involved so let s
59. is usually not human readable JRuby also includes an AOT compiler usable for obfuscation for gener ating real Java classes from Ruby code or for deployment to environ ments that don t support the JIT compiler The Android mobile plat form is an example of such an environment We ll explore JRuby s AOT compiler later in the chapter JRuby s Compiler In JRuby almost all code starts out interpreted But as the program runs JRuby looks for functions that would benefit from being compiled and compiles them Readers used to the HotSpot JVM will find this approach familiar Let s look at an example Here s a simple benchmark that iterates through all the permutations of a string Download compiler jit permute rb require benchmark def do_something_with data Your favorite operation here end 5 times do timing Benchmark measure do letters F s a els e s Es S7 letters each_permutation do p do_something_with p end end puts timing end The implementation uses Ruby s blocks to perform the iteration 2 For more on how blocks work see Appendix A on page 272 Report this copy is P1 0 printing Janua COMPILER 101 Download compiler jit permute rb class Array Calls the attached block of code once for each permutation def each_permutation amp block We ll need to permute the array L times factorial 1 length inject 1 p n p n Make
60. is for content In the Edit pane we can write plain text with a little basic markup for example asterisks for bold text The Preview pane shows what the end result will look like after we apply all the formatting 1 No pun intended Report erratum this copy is P1 0 printing January 2011 m Edit Preview It was the vest of times it was the wurst of times Add Chapter Figure 10 1 Swing Interface Ready to see the code Let s start by bringing in a few libraries and classes we ll need Download guis swing bookie rb require java require rubygems require redcloth classes w JFrame JButton JList JEditorPane JSplitPane JTabbedPane JTextPane DefaultListModel ListSelectionModel BoxLayout text htm HTMLEditorKkit classes each do c java_import javax swing c end java_import java awt Dimension First we load the java library This lets us java_import a few Swing classes for convenience Notice that we re also loading a gem called redcloth RedCloth is an implementation of Textile a wiki like markup language Go ahead and install that now while we re on the subject jruby S gem install RedCloth From this point on the majority of the code is just laying out the GUI and spelling out behavior We ll be using stock Swing techniques here 2 http redcloth org this copy is P1 0 printir You ll see plenty of places where a Ruby framework could
61. java util HashMap class HashMapTestCase lt Test Unit TestCase def setup map HashMap new end def test_new_hashmap_is_empty assert map isEmpty end def test_hashmap_with_entry_is_not_empty map putC hello world assert map isEmpty end def test_value_is_associated_with_added_key map putC hello world assert_equal world map get hello end def test_entry_set_iterator_next_raises_error_for_empty_hashmap assert_raises NativeException do G map entrySet iterator next end end end Here s a fragment you can add to your Ant build file to run these tests Download beyond_unit_tests junit_integration build xml lt target name test depends compile description Compile the source files for the project gt lt junit haltonfailure false fork yes gt lt classpath refid run classpath gt lt formatter type plain usefile false gt lt test name TestUnitSuite gt lt junit gt lt target gt srratum opy is P1 0 prin WRAPPING UP lt 239 Ready to run some tests ant test Buildfile build xml compile test junit Testsuite TestUnitSuite junit Tests run 4 Failures 0 Errors 0 Time elapsed 8 615 sec junit junit Testcase test_entry_set_iterator_next_raises_error_for_empty_hashmap junit Testcase test_hashmap_with_entry_is_not_empty HashMapTestCase took junit Testcase test_new_hashmap_is_empty HashMapTestCase took 0 005 sec junit
62. libraries you re using This kind of problem can also happen if a class you re directly or indi rectly depending on was compiled for an incompatible JVM version Can t Find the Method A lot of things can go wrong at method invocation time The most obvi ous thing to check is the method name if you can call a method by its original Java camelCase name but not by its Ruby style snake_case name you may be looking at an edge case in the mapping between the two like setURLForPage set_urlfor_page After spelling quirks the most common cause of vanishing methods is type coercion If JRuby can t automatically map your Ruby parameters to Java ones it won t call the method You ll need to convert some of the parameters yourself Wrong Method A less frequent case but no less baffling when it happens is when JRuby invokes a different method than the one you want As we saw earlier JRuby tries to pick the closest match among overloaded func tions But some distinctions simply do not exist on the Ruby side Similar situations can come up when multiple overloads are all equally valid such as when a Ruby object implements two interfaces and there are overloads for each In cases like these you ll need to use java_send or one of its cousins from Section 2 6 Forcing a Specific Overload on page 52 JRuby can also end up making the wrong call if your Java method names clash with common Ruby ones Say you have the followi
63. like com org java and javax To use these you have to require java first Download java_from_ruby loading_classes rb require java java lang StringBuffer gt Java JavaLang StringBuffer If the class you want to access lives in the default package that is no package specifier at all just prepend Java directly to the class name Download java_from_ruby loading_classes rb Java MyTopLevelClass gt Java MyTopLevelClass It s worth noting that the module namespace for a given package is just another Ruby object Report erratum LOADING CLASSES You can stash it in a variable or pass it around at will Download java_from_ruby loading_classes rb swing javax swing swing JFrame gt Java JavaxSwing JFrame The techniques in the next section will build on this idea of treating module and class names like regular data By Importing For classes nested deeply inside namespaces you may get tired of typ ing out the full module or package name every time A common con vention is to define a new constant consisting of just the class name Download java_from_ruby loading_classes rb StringBuffer java lang StringBuffer JRuby provides a handy java_import shortcut that does exactly this kind of assignment You can indicate the class you want using a Ruby con stant a Java package name or a string Download java_from_ruby loading_classes rb java_import java lang StringBuffer java_im
64. lot of applications on the Web or elsewhere With ActiveSupport you can express a time difference as easily as 2 months 1 day 3 hours 15 minutes ago Compare that to old school time arithmetic Time now 2 30 24 3600 24 3600 3 3600 15 60 and that doesn t even take into account that different months have different lengths ActiveSupport is chock full of nice things like this As you become familiar with it you ll often find that some utility function you ve been wishing for is already included ActiveResource In the bad old days we tended to think of web apps as little com puter programs churning out HTML tag soup You can write a program like this with Rails of course But you will find it far eas Report erratum 1 0 printing January 2011 WHat Is RAILS lt 103 ier to cut with the grain and think in terms of resources instead of pages or scripts This style is known as Representational State Transfer REST Rails makes it easy for you fit your app into this structure Action Pack helps you create REST services and ActiveResource helps you consume them both under similar APIs ActionMailer ActionMailer is a small package that helps you create uniform mail templates You can send mail from your controllers and use erbo files as templates for your messages ActiveModel ActiveModel is a new component created in Rails 3 that is basi cally an extraction of the best bits of ActiveRecor
65. main database libraries for Ruby are quite different from one other ActiveRecord is a high level framework that allows you to work with the database abstracted away at least to a degree Its name comes from a pattern in Martin Fowler s Patterns of Enterprise Application Architec ture Fow03 DBI and Sequel both allow you to work much closer to the database Although you won t have to deal with a specific database product s wire protocol or file format you ll have much more control over the exact SQL queries your Ruby program will be running The differences listed earlier should make it clear that these libraries are suited for very different circumstances and it s good to keep a cou ple of them in your toolbox But wait with that decision until you have seen the tools available only on JRuby ActiveRecord In Chapter 5 Introduction to Rails on page 98 we saw just enough ActiveRecord to get a Rails app running Let s dive in a little deeper now We ve said that this library is an implementation of the Active Record software pattern what does that mean For the purposes of this chapter we re going think of object oriented programs in terms of model classes and utility classes Model classes represent the ideas behind your program in language similar to what you d use with an end user blog posts employees appointments and 1 Another great Ruby data library DataMapper also gets its name from Fowler s book
66. may be wondering whether other Ruby mechanisms can load Java code Indeed they can Both the argument and the SLOAD_PATH vari able work on both Ruby and Java libraries in JRuby jruby I path to e require library jar C gt jruby IC path to e require library jar Download java_from_ruby classpath rb LOAD_PATH lt lt usr local lib jemmy require jemmy jar Report this copy is P1 0 printing January LOADING CLASSES Now that JRuby knows where on disk to look for external libraries how do we crack them open and get at the classes inside 2 3 Loading Classes Your Ruby code will see Java packages as Ruby modules This is not surprising because these are the fundamental namespace mechanisms of the two languages Let s take a closer look at how this works By Namespace The most reliable way to refer to a Java class in JRuby is by tacking Java onto the beginning of the full package name Download java_from_ruby loading_classes rb Java clojure lang Rep1 gt Java ClojureLang Repl Notice JRuby has translated the Java like clojure lang Rep syntax into an internal name Java ClojureLang Repl It may be tempting to cut out the middleman and use the latter name directly in your code but we don t recommend it Internal formats are subject to change but the package name syntax will always work For the most commonly used namespaces JRuby provides top level functions
67. method on the first line You ll often use this flag for loading Ruby standard libraries especially in one liner scripts passed to e C directory With this flag JRuby will switch to the specified directory before begin ning execution 2 The path separator is a semicolon on Windows and a colon basically everywhere else Report erratum COMMAND LINE OPTIONS lt d 297 UNIX style shebang lines work with JRuby only if you ve installed the native launcher You can do this by using one of the official JRuby installer packages or by running jruby S gem install jruby launcher C During development you may want to check that a script is syntacti cally correct without actually running it The c flag does exactly that checking the syntax of the provided script and either reporting errors or printing the text Syntax ok and exiting y or yydebug These flags turn on verbose parser debugging in JRuby s parser It might be helpful if you have a really peculiar syntax error and can t figure out why but otherwise you ll probably never need them S The simplest way to process command line parameters may be to use the s flag The s flag turns on basic argument processing doing the following for you e Simple flags like foo set the same named global variable to true the equivalent of foo true in this case e Name value flags like foo bar set the same named global to the string value specified
68. mocks are allowed to cause a test failure For more complete explanation see Martin Fowler s article Mocks Aren t Stubs http martinfowler com articles mocksArentStubs html their dependencies on outside software The conventional way of solv ing this problem is to use test doubles which are stand ins for exter nal code In Java this process usually requires designing your appli cation around interfaces and then providing fake implementations mocks and stubs that return canned values Ruby s open classes make it easy to replace an object s methods at runtime This capability is useful for creating mocking frameworks since we don t have to rely on Java interfaces We can just replace individual methods that would normally talk to an external service Since Java doesn t support Ruby s level of metaprogramming some of our favorite mocking and stubbing techniques aren t available in JRuby For instance you can modify a Java class in Ruby but those modifications will be visible only on the Ruby side Java won t be able to see them Fortunately there are still plenty of things that do work fine with Java Let s take a look at a couple RSpec Mocks RSpec comes with its own mocking and stubbing framework which works well in JRuby You ll run into some limits when youre testing Java code though we ll see what those limits are in a minute 6 http xunitpatterns com Test 20Double
69. most common uses described earlier and then just let JRuby delight you For those rare times when you really need to know exactly what s happening inside the machinery you can turn to Appendix B on page 290 2 6 Calling Overloaded Methods There are two reasons JRuby looks so closely at the parameters you pass into Java methods The first as we ve just seen is to expose your 11 Speaking of threads we should mention that JRuby is not subject to the Global Interpreter Lock shared by some Ruby implementations Your Ruby threads can run simultaneously on multiple cores this copy is P1 0 printing Ja CALLING OVERLOADED METHODS Ruby data to Java in the most convenient way possible The second is to select the best match for an overloaded method Automatic Resolution The simplest case to consider is a set of overloads based on a single parameter where the differences among types are obvious Download java_from_ruby OverloadDemo java import java util List public class OverloadDemo public static String whatTypeIs long value return long i public static String whatTypeIs String value return string public static String whatTypeIs Object value return object Here the Java types are radically different from one another and JRuby is able to choose appropriate overloads with no assistance Download java_from_ruby overload_demo rb OverloadDemo what_type_is 42 gt l
70. of manual work You have to paste your tested Ruby code into the java file write a bunch of methods with names matching the Ruby ones and possibly add a bunch of conver sion code to get your Java data into Ruby compatible structures Fortunately JRuby s compiler makes all those manual steps unneces sary If you pass the java option to jrubyc it will generate a java file instead of a class file You can then fall back on familiar Java tools to finish the job jrubyc java waveform rb Generating Java class Waveform to Waveform java javac cp jruby jar Waveform java As you can see we generated a file called Waveform java and then com piled this file like any normal Java source code But it s not obvious how to call it this copy is P1 0 printing Jar A SIMPLE COMPILED EXAMPLE Look at the signatures of the generated methods public Waveform Object points YI goats public Object rmsQ TT asa Recall that Ruby function definitions don t specify argument types Without this information jrubyc has to fall back on Object for the parameters and return values The Ruby code to initialize a Waveform instance is expecting an array of numbers How do we inform the com piler of that expectation All we have to do is tag the Ruby functions with java_signature followed by a string containing a Java function declaration Here s how that would look for the Waveform class Download compiler wavef
71. on the passed in parameters Types that map directly between Ruby and Java get preferential treatment For instance Ruby Fixnums match Java integer types both primitive and boxed Ruby strings match Java strings and so on If no direct mappings exist JRuby tries a looser fit by converting be tween different numeric types For a Ruby Integer with no corresponding Java int or Integer argument JRuby will look for a Java Numeric As a last resort JRuby looks for parameters that are Java interfaces and attempts to implement those interfaces on the fly B 2 Parameter Types For a number of basic types JRuby performs automatic conversions in both directions across the Java Ruby boundary JRuby uses the mapping in Figure B 1 for selecting among overloaded methods and for converting parameters this copy is P1 0 printing January 2011 xclusively for Shohei Tanake RETURN VALUES lt 292 Ruby Type Java Type Notes java util List Array java util Collection or a primitive array Similar precision guarantees to Float and Fixnum conversion Applies only to the last parameter If a target method takes an interface type JRuby will Any type Any interface type attempt to implement the interface around the passed in Ruby object Java Class objects imported java lang Class into Ruby Actual type or o java lang Object i e no conversion Figure B 2 Other Types Java Type Diff
72. one language to another The obvious downside is inelegance If you have a small clean Ruby script then the extra step of constructing a Java class for the sole purpose of returning results will feel like makework If on the other hand you can build a simple Java class that doesn t look too out of place alongside your Ruby code then go for it Type Coercion Pitfalls JRuby strives to do the right thing with type coercions As you call into Ruby code and as that Ruby code returns data back to Java many types will get implicitly converted to similar types in the other language This approach is not however immune to mishaps Once an object is coerced to another type no matter how similar it really is a different object Code that relies on object identity will not work right For exam ple Maps may not work as you expect We ve discussed a lot of doom and gloom scenarios in this section While these are important to keep in mind remember that for the most part things will just work If you go about your project armed with the knowledge of which subtleties can bite you and what to do about them you ll be fine 12 Anyone remember the original EJB specification Report erratum WRAPPING UP 3 4 Wrapping Up In this chapter we looked at the various ways to call from Java into Ruby all in the context of a real life example We then highlighted a couple of specific features of JRuby embedding that may he
73. order to tell my searches apart As a person who browses in multiple tabs I want to see the term I searched for Scenario Page title Given I am on the search home page When I search for hello world Then the page title should begin with hello world Cucumber stories tend to follow a certain rhythm They begin with some optional documentation about the feature you re testing The important parts are the clauses that begin with Given When and Then which define the different parts of the story The actual implementations are in a Ruby step definition file We ll get to that in a second but first let s run the story as is Save the story as search feature and run the following commands jruby S gem install cucumber rspec jruby S cucumber search feature Youll get a report that contains a copy of the original test script fol lowed by the pass fail results Feature Web search In order to tell my searches apart As a person who browses in multiple tabs I want to see the term I searched for Scenario Page title Given I am on the search home page search feature When I search for hello world search feature Then the page title should begin with hello world search feature 10 search feature OH Oo ON 1 scenario 1 undefined 3 steps 3 undefined Om0 238s this copy is P1 0 printing WRITING HIGH LEVEL TESTS WITH CUCUMBER lt 220 AA E Ola Says Cucumber and the RSpec Story Runner befo
74. packaged into a single archive why not extend that portable goodness to web applications Warbler is a packaging tool that does just that If you re a Java web developer you re familiar with web archives Web archives usually called war files are the web application equivalent 5 http rawr rubyforge org this copy is P1 0 printing PACKAGING FOR DEPLOYMENT lt 188 of jar files war files are simply zip format files with web content for example images and style sheets in addition to application code De ployment of a war file usually means simply presenting the file to your Java application server either by copying it into a blessed autodeploy directory or by using a deployment tool specific to the server you re using Every war file has a common structure The root directory of the archive is the document root where you place html css JavaScript images and any other static content that your application requires The archive has a specially named WEB INF directory that contains application code including Java classes Java jar libraries configuration files and any other content that you don t want to be directly visible to your end users Contrast this structure with the one we ve already presented for Rails applications The root of a Rails application contains directories like app and config full of code and configuration along with a single public directory that represents the document
75. paths from revisions from ruby_from_java historian lib git lib rb 249 in diff_full from ruby_from_java historian lib git diff rb 100 in cache_full from ruby_from_java historian lib git diff rb 106 in process_full from ruby_from_java historian lib git diff rb 64 in each from ruby_from_java historian lib archive7 rb 10 in history from lt script gt 1 Couldn t generate diff please see the log file So there you have it a program written in Java that calls a Ruby method to inspect the source code of the program itself We will be cov ering some more details for the rest of this chapter but you largely have all the skills you need now Go forth and make some simple embedded Ruby applications or read on for the nitty gritty details 3 2 The Nitty Gritty There are always special circumstances and strange little details that a project runs into If you find yourself wanting more control knobs for the embedding API than we ve shown you so far then read on Other Embedding Frameworks All the examples we ve seen so far have used Embed Core the main embedding API that ships with JRuby This API offers a great deal of interoperability You can call a Ruby method crunch the results in Java and hand data back into Ruby What makes this deep integration possible is that Embed Core was created just for JRuby There are times however when a general scripting API is a better fit than a Ruby specific one For instance if you
76. placed a nearly empty class in that file this copy is P1 0 printing MONKEYBARS lt 259 Tom Says Relying on update_view is an intentional design decision of the Monkeybars team In traditional MVC applications views would automatically get updated whenever a model would change Once an application gets really large these updates can be frequent and unpredictable especially if one model has com plex relationships with another model Giving the developer control makes updates easier to manage There is however a shortcut for the cases when you know it s OK for Monkeybars to call update_view automatically just append to the method name for you All the mods you ll make will go inside that existing class defi nition Let s start with the handler for the Add Chapter button Download guis monkeybars src bookie bookie_controller rb def add_chapter_action_performed model text view_model text model add_chapter update_view end This snippet highlights one of the most convenient aspects of Monkey bars programming The act of defining a function with this exact name means that Monkeybars will automatically call add_event_listener on the add_chapter button for us This shortcut follows a convention over con figuration philosophy similar to the Ruby on Rails framework In the body of the event handler we save the contents of the Edit win dow into the current chapter and then tell the model to ad
77. rb require ffi module CMath extend FFI Library ffi_lib Tibm attach_function pow double double double end puts CMath pow 2 0 8 0 gt gt 256 0 1 http wiki github com ffi ffi 2 http rubini us Report erratum FOREIGN FUNCTION INTERFACE lt 311 The syntax is such a natural fit for Ruby that the JRuby team decided to put FFI in the official JRuby build That means if you code to this API you can call into C from at least four different Ruby implementations A Windows Example We re not going to cover all the ins and outs of FFI But if we show off a couple of common scenarios we can hit most of the high points Let s start with a really simple Windows example that just shows a couple of the basics of FFI calling conventions and string parameters The following code will print the title of the topmost window Download ffi windows rb require ffi module User32 extend FFI Library ffi lib user32 ffi_convention stdcall typedef pointer hwnd attach_function GetForegroundWindow hwnd attach_function GetWindowTextA hwnd pointer int int end FFI MemoryPointer new char 1000 do buffer hwnd User32 GetForegroundwindow User32 GetWindowTextA hwnd buffer buffer size p buffer get_string 0 gt gt jruby Cmd end As with the previous example we gather related functions from one external library into a single module Since this is a Windows libra
78. rb 28 in test_spec an empty HashMap 003 should associate hashmap_test_spec rb 26 in run this copy is P1 0 printing Jc RUBY TEST FRAMEWORKS lt 207 lt world gt expected to be to lt world gt 4 tests 4 assertions 1 failures 0 errors We now get an explanation based on the context and description of the test case rather than just a method name With test spec you can sneak these nice RSpec like features into established projects that are already using the Test Unit infrastructure shoulda Both RSpec and test spec are significant departures from the style of Test Unit What if you d rather stay on familiar ground and use the Test Case class to group your tests but still gain some flexibility Like nest ing groups of tests or writing test methods with nicer looking names Shoulda is a small framework that gives you exactly these benefits plus the ability to add test macros This last feature has made it one of the main testing frameworks for Rails applications When the most common kinds of tests are already written for you your own tests end up communicating your intent quite concisely The main difference between Test Unit and Shoulda is in the way you write tests Instead of defining new methods for tests you pro vide blocks that include the test code You still use the assertions that Test Unit provides and whichever mocking framework you like Now that we know what Shoulda is l
79. re still using the blunt instru ment of raw strings to pass data back and forth though Let s change that Real Java Data Odds are that in any nontrivial application you ll want something more substantial to chew on than just an Object you call toString on Let s change our example to return something useful to Java A REAL LIFE EXAMPLE SOURCE CONTROL First we ll make a Java interface to represent a diff for each file in a Git changeset Download ruby_from_java historian src book embed GitDiff java package book embed public interface GitDiff public String getPath public String getPatchQ Of course the Ruby Git library s Difffile class was written long before the GitDiff Java interface But we can reopen the Ruby class and make it implement the interface using the techniques in Section 2 7 Imple menting the Methods on page 54 Download ruby_from_java historian lib archive5 rb require git class Git Diff DiffFile include Java book embed GitDiff end def history git Git open git diff revisions start revisions finish to_a end The DiffFile class in Ruby already has path and patch methods defined When we implement GitDiff by include ing it in DiffFile Java will automat ically have access to the existing path and patch methods via getPath and getPatch No need to write any wrappers or define any mappings As we saw earlier the diff method will return a Ruby Array
80. root of the application It s as if a web archive is the Rails application structure turned inside out And so this is the primary function of Warbler to take a directory con taining all the loose files and directories of a Rails application and turn it into a war file that will run in any Java application server Getting Started The whole point of Warbler is to make it easy to get started from Rails application to war file in one command First you need to install the warbler gem Download rake sessions gem_install_warbler txt jruby S gem install warbler Successfully installed jruby jars 1 5 Successfully installed jruby rack 1 0 Successfully installed rubyzip 0 9 4 Successfully installed warbler 1 1 0 4 gems installed 0 1 You probably noticed the jruby jars and jruby rack gems in the list of things that got installed more on that in a bit The warbler gem gives you a warble command So now we can go ahead and run it on our rouge application from Section 5 2 Going Rouge on page 105 Report erratum P1 0 printing January 2011 PACKAGING FOR DEPLOYMENT Download rake sessions warble_rouge txt jruby S warble rm f rouge war Creating rouge war And within seconds we ve got a stand alone dependency free rouge war file ready to deploy to a Java application server Let s peek at some of what s inside Download rake sessions rouge_contents txt jar tf introduction_to_rails rouge rouge wa
81. sits on top of Swing Although it knows about Swing it tries to shield you from it as much as possible In this sense Monkeybars feels more like a framework in its own right than just a Swing add on This abstraction has its pluses and minuses as we ll see Part of Monkeybars appeal is that it plays nicely with Matisse the GUI editor built into the NetBeans IDE While you can certainly write a Mon keybars program without Matisse we d like to show you how much rote layout code you can skip by using a graphical editor One thing we d like you to keep in mind while you re writing code in this section is the emphasis on separating concerns The data at the heart of the application the user interface and the logic connecting them are three separate entities This kind of design lends itself well to scalable testable GUIs Project Structure To get started make sure you have a version of NetBeans installed that has both Ruby and Java support The easiest way to do this is to download the Full edition but you can also add either language to your existing installation through the Tools Plugins menu item Next install the Monkeybars gem plus a packaging helper called Rawr jruby S gem install monkeybars rawr Now create the overall structure for your project Run the following commands in order some may take a few minutes to finish jruby S monkeybars bookie cd bookie jruby S rawr install jruby S rake gene
82. static 272 273 passing to Java 291f 291 292 return values from Java 292f 292 in Ruby 272 273 281 283 see also type conversions data validation 115 142 145 database adapters 136 database frameworks 133 164 DBI 146 150 debugging jdb debugger 299 JRuby options 298 299 308 dynamic types 272 273 editors 26 Emacs 26 Embed Core framework 70 embedding strategies 74 76 environment variables CLASSPATH 39 RUBYOPT 39 event listeners in Rubeus 248 249 in Swing 244 246 executions Maven 181 expectations in Mocha 216 in RSpec 202 in RSpec Mocks 214 extension API 309 F FFI Foreign Function Interface 309 314 filename case sensitivity 90 Go gems managing with Bundler 108 109 managing with Maven 182 packaging with Warbler 192 Git 61 GlassFish 189 GUIs Graphical User Interfaces Limelight framework 260 268 Matisse GUI Editor 251 255 Monkeybars framework 250 260 Rubeus framework 246 250 Swing API 241 246 H Hibernate 155 156 HTTP Basic Authentication 120 122 I IDEs integrated development environments 26 28 inheritance 276 installing JRuby 21 23 instance field mapping 45 instance method mapping 44 instance variables 276 integration testing 218 220 interactive shell 24 interpreter functions 79 Loo jar files building with Ant 178 building with JRuby 185 187 Java integration see Ruby driving Java Ruby from Java Java runtime
83. subdirectory Wrong Version of a Class Maybe it s happened to you You make a change to a Java class to fix a bug and it doesn t work You throw in some printin statements to find out what s going on and nothing shows up on the console Is JRuby even calling your code Perhaps not If some other implementation of that class inside some other directory or jar is ahead in the classpath JRuby might be loading that and not even seeing your work Errors at Construction Time Sometimes JRuby will import a class just fine but will raise a NoClassD efFoundError or LinkageError when you try to instantiate it This can hap pen when the class you need is in your classpath but one of its depen dencies isn t For example imagine you have a file named consumerjar containing a Consumer class Even after JRuby finds the jar things can still go wrong Download java_from_ruby producer_consumer rb consumer Consumer new gt Consumer java 2 in lt init gt java lang NoClassDefFoundError gt Producer NativeException gt Bans gt from 7 Here the backtrace provides a clue Java couldn t find a Producer class which Consumer apparently requires Adding producerjar or wherever the class lives to your classpath should fix the problem If the back Report erratum TROUBLESHOOTING trace doesn t give enough clues to figure out which jar is missing it s time to hit the documentation for the Java
84. tell the tab control to switch tabs For this case we ve put the common code into a prop type called DualPane and specified a couple of its method names directly in props rb Download guis limelight bookie bookie props rb tab_button text gt Edit tid gt edit_tab on_mouse_clicked gt scene dual_pane edit styles gt left tab tab_button text gt Preview tid gt preview_tab on_mouse_clicked gt scene dual_pane preview styles gt right_tab Each of these two buttons asks the dual_pane prop to execute a differ ent method Note that props can find one another through the scene attribute You may be wondering whether you can put any arbitrary code into props rb Indeed you can You could put all your styles and behavior into this file but we don t recommend it We suggest using this kind of inlining for the simplest cases only In truth we have only scratched the surface of Limelight but we hope you have a foothold in understanding how its parts fit together 10 6 Wrapping Up GUI development is an area of JRuby programming that grows more exciting daily as new toolkits pop up Mainstream Ruby s lack of a strong cross platform GUI is one reason people are migrating to JRuby Once you ve decided to use Swing you still have find the right Ruby framework to use with it Let s consider the frameworks we ve looked at and try to identify why you might find each one appealing Raw Swi
85. the control The using option in Monkeybars is meant for exactly this kind of filtering Download guis monkeybars src bookie bookie_view rb map view gt preview text model gt text tusing gt redcloth nil def redcloth text RedCloth new text to_htm end The nil parameter by the way refers to data going the other direction from the GUI back into the model Since this is not an editable window we don t care about fetching data from the GUI For the view to find the RedCloth library we re going to have to copy some code into the project directory The easiest way to do this is with the gem unpack command followed by a rename We ll just show the UNIX version of this because the Windows version is similar move instead of mv jruby S gem unpack RedCloth target 1ib ruby mv 1lib ruby RedCloth 4 2 3 universal java lib ruby redcloth Then you ll need to add these lines at the end of src manifest rb to tell it to load the library Download guis monkeybars src manifest rb add_to_load_path lib ruby redcloth lib require redcloth Now here s the code to connect the currently selected chapter in the GUI chapters selection_model single_index to the currently selected chap ter in the model index Download guis monkeybars src bookie bookie_view rb map view gt chapters selection_model single_index model gt index Report this copy is P1 0 printing Janua MO
86. the convention What if that isn t the case or what if you want to have associations to other model classes Ribs allow you to handle these sorts of customizations too of course but you need to provide some mappings for the process to work Over the next few pages we ll look at a few of the more common relationships you can express The definitions for a model class go inside a block attached to the Ribs method Before we get to the contents of the block let s look at the method s options Report erratum Download databases ribs_mappings rb class Blog Ribs table gt wp_blog identity_map gt true do blog mappings go here end end The most commonly used option is table which specifies the name of the database table for this model The other setting shown here iden tity map makes sure that any given row in a database will always be represented by the same Ruby instance This makes object compari son easy but can cause surprises in code that expects more traditional Ruby behavior The mappings themselves go inside the block We describe the database structure by calling methods on the Rib object that Ribs passes to us The first settings we ll change have to do with column names Download databases ribs_mappings rb blog blog_id primary_key blog title column gt blog_title Here we set the blog_id column as the primary key We also map the title Ruby attribute to the blog_t
87. the Libraries category and then select Add Library Choose Swing Layout Extensions the GUI editor needs these exten sions Now click Add JAR Folder and select both jruby complete jar and monkeybors jar from within your lib java directory Whew Quite a bit of setup but it will pay off when we sketch out our GUI in Matisse Let s do that now User Interface Expand the Source Packages list under the project name Right click the bookie package and choose New JFrame Form Type Bookie for the form name and then click Finish NetBeans will open a layout screen that should look something like Figure 10 2 on the next page The gray rectangle in the middle of main screen is the new GUI layout This is where you ll drag controls from the palette Let s start with the Split Pane since it will contain most of the other components Drag a Split Pane from the palette into the layout area Resize it until it fills up Report erratum 1 0 printing January 2011 MONKEYBARS lt 252 00o Bookie NetBeans IDE 6 8 j lt default conf ER T Qr Search 38 1 Proj OO Files Services C Bookiejava Palette ce v amp Bookie k source posam Swing Containers v i Source Packages Dis e E gt E lt default package gt _ Panel E Tabbed Pane v E bookie JL Split Pane Scroll Pane E Bookie java 6 bookie_controller rb E Tool Bar 5S Desktop Pane E
88. the equivalent of foo bar in this case The s flag is normally used in a scripts shebang line as in the fol lowing example usr local bin jruby s Greets the person named by the name option print Hello name Report erratum is copy is P1 0 printing Ja COMMAND LINE OPTIONS lt d 298 K a Charlie Says Why isn t set_trace_func enabled by default Because it requires that JRuby check for an installed function before and after every call on every exception raised at every line and on entry into every class body The majority of scripts never use this functionality so we avoid this performance hit by default If you use s on the command line instead of a shell script you need to use two dashes to separate the arguments meant for JRuby from the ones meant for your Ruby code jruby s e puts foo bar foo bar baz true baz In the previous example s and e are options for JRuby and foo and bar are specific options for this program d or debug This option turns on debug mode both by enabling additional internal logging for JRuby and by setting the SDEBUG global variable for use by your program Optional logging like this is useful at development time to get a bit more information out of JRuby or third party libraries It s also a great way to add debug logging to your own programs you never know when it might save you The same flag also sets up JRuby f
89. the techniques you used in Chapter 3 Ruby from Java Embedding JRuby on page 60 In the next section we ll get to know the AOT compiler by trying it on a simple project Report erratum A SIMPLE COMPILED EXAMPLE 4 2 A Simple Compiled Example Over the course of this section we ll start with a simple Ruby example and explore different ways to compile it for the JVM Compiling a Single JRuby Class Let s say you re a home audio enthusiast and want to make some basic measurements of your setup In particular you may be interested in the root mean square RMS voltage of a signal you ve captured Download compiler waveform waveform rb class Waveform def initialize points points points end def rms raise No points unless points length gt 0 squares points map p p p sum squares inject s p s p mean sum squares length Math sqrt mean end end What does it mean exactly to ask JRuby to compile this code jrubyc waveform rb Compiling waveform rb to class waveform This will place a waveform class file in your project directory This file can be used in place of the original rb file Go ahead and try it Rename your Ruby file to backup ro or something and then run the following Download compiler waveform waveform_test rb require waveform sine_wave 0 360 map do degrees radians degrees Math PI 180 0 Math sin radians end waveform Waveform new sine_
90. time Opinionated Software All of these slogans and buzzwords tie into each other They all have the common goal of establishing the easiest and best way to develop web applications according to one opinionated person David Heinemeier Hanson He started the Rails project with very specific ideas about what s good and what s bad in a web frame work Of course thousands of volunteers have improved Rails over the years but its overall shape is still guided by these opinions One example of opinions in Rails is the lack of support for compos ite primary keys in the database If you really need them they re available as a plug in but the Rails team has resisted bloating the core libraries with them Most things are possible in Rails but dubious practices result in uglier code than sound practices do Suspect code will therefore really stand out when you re writing it Components Under the hood Rails is not really one framework Rather it s a compo sition of several loosely tied libraries that happen to work well together Here are the major Rails libraries ActiveRecord The ActiveRecord library covers the model part of the MVC pat tern by pairing database tables with simple wrapper classes that embody your program s logic The implementation makes partic ularly good use of Ruby language features and takes most of the pain out of defining model classes ActiveRecord supports most standard database features but no
91. to find selectionMode Change it to SINGLE Now you ll need to make a similar round of changes to the Preview window the white area in the second tab e document Custom code preview getEditorkit0 createDefault Document e editable Uncheck this option e editorkit Custom code new javax swing text html HTMLEditorkitd Report erratum MONKEYBARS lt 255 With those changes we re done with the layout and can finally add some Ruby code Before we do though let s go back over a couple of key observations about this process First using the graphical editor has made it easy to get our layout drawn clearly But once the initial sketch was done the baroque details of Swing API started to rear their heads again For this project the speed of creating a nice interface was worth the few extra seconds ferreting around in the property dialogs This may not be the case for all projects though Fortunately the method for hooking Monkeybars up to a GUI is the same no matter whether that GUI was generated from Matisse or written by hand Kicking the Tires Before we give life to all these controls let s add just enough Ruby code to get the app running The first thing Monkeybars needs is the name of the GUI class you drew in NetBeans Open src bookie bookie_view rb and change the set_java_class line so that the contents of the file look like this class BookieView lt ApplicationView set_java_class bookie Bookie
92. to start your application You can specify this by setting config webxml booter to rails rack or merb config webxml booter rack Remember that we glossed over the details of web xml except to say that it s generated for you Let s take a slightly closer look now web xml is where Warbler places several key value pairs to tell JRuby Rack how to boot the application The config webxml object gives you a place to add any other parameters that need to go into this file For example setting config webxml rails env staging has the effect of ren dering the following fragment inside the war file s web xml file Report erratum 0 printing Jar PACKAGING FOR DEPLOYMENT lt 195 lt context param gt lt param name gt rai1s env lt param name gt lt param value gt staging lt param value gt lt context param gt One other pair of config webxml settings you may want to take a look at is jruby min runtimes and jruby max runtimes JRuby Rack uses these to decide how to service requests in a Rails application Prior to Rails 2 2 the internals of Rails were not safe for concurrent execution by multiple threads Rubyists traditionally dealt with this limitation by running several single threaded Ruby processes at once the so called pack of Mongrels approach With JRuby the Ruby inter preter is just a regular Java object we can easily create several inside a single JVM JRuby Rack can then pool multiple J
93. typedef int sigset_t class SigAction lt FFI Struct layout sa_action_u SigActionU sa_flags tint Sa_mask zint end We re almost ready to call all these elaborately built up functions FFI provides a Function class that we can pass into the C functions to serve as a callback Here s how we set up the two structs we need action for the input and out for the output this copy is P1 0 printing FOREIGN FUNCTION INTERFACE lt 314 Download ffi posix rb handler FFI Function new void int i puts RING action POSIX SigAction new action sa_action_u sa_handler handler action sa_flags 0 action sa_mask 0 out POSIX SigAction new Finally we can make our calls sigaction tells the OS which function to call when we receive a wakeup signal and alarm will fire that signal one second into the future Download ffi posix rb SIGALRM 14 POSIX sigaction SIGALRM action out POSIX alarm 1 puts Going to bed sleep 2 puts Breakfast time When you run the program you should see the messages one at time with a brief delay in between jruby posix rb Going to bed RING Breakfast time If you re porting this code to another operating system some of these data type definitions will need to change The linux rb file that comes with this book s source code shows one example of the kinds of modifications you might make Calling into an unsafe language from
94. usual with Rails you get several things for free including a basic test file and a skeleton in which to put the database definitions for the model Since Rails defines models by their database structure we need to create a table before using the model This is done in the file db migrate _create_restaurants ro For now you should edit it to look like this code example BUILDING OUR MODELS 112 Download introduction_to_rails edits 001_create_restaurants rb class CreateRestaurants lt ActiveRecord Migration def self up create_table restaurants do t t string name t text description t string address t string phone t timestamps end end def self down drop_table restaurants end end Notice that the migration describes the data s structure in Ruby with out referring to any particular database product Each migration should perform a single unit of database work and should include a way to undo that work so that the migration can be rolled back In the previous example we create or remove a table called restaurants The next step is to run this migration and thus create the database table We do so using rake with the db migrate target Download introduction_to_rails output rake db migrate 1 txt jruby S rake db migrate Cin code introduction_to_rails rouge CreateRestaurants migrating s s s s s s SSS s s create_table restaurants gt 0 0290s gt 0 ro
95. who wants to take their art to the next level Read it gt Geoff Drake Owner Managed Design This is one of those books that you don t want to put down and you can t wait to get back to For a technical publication that is extremely rare Usually I find myself having a hard time trying to stay awake After reading this book I can say I have a very good understanding of what JRuby is how it interacts with Java and a working knowledge of many of the supporting tools to accomplish a wide range of tasks The way this book is organized it makes a great reference for future development gt Gale Straney Senior software design engineer Tektronix This book makes a compelling case for JRuby A must have to bring some Ruby goodness to your Java powerhouse gt Fred Daoud Author Stripes and Java Web Development Is Fun Again and Getting Started with Apache Click This book is an excellent resource for JRuby and will without a doubt facilitate JRuby adoption in Java centric enterprises gt Bharat Ruparel Senior information architect America s Test Kitchen Prepared exclusively for Shohei Tanaka Using JRuby Bringing Ruby to Java Charles O Nutter Nick Sieger Thomas Enebo Ola Bini Ian Dees The Pragmatic Bookshelf Raleigh North Carolina Dallas Texas Pr matic ookshelf Many of the designations used by manufacturers and sellers to distinguish their prod ucts are claimed as trademarks Where tho
96. 00 Guide to Design Tools and Techniques JavaScript is now a powerful dynamic language with a rich ecosystem of professional grade development tools infrastructures frameworks and toolkits You can t afford to ignore it this book will get you up to speed quickly and painlessly Presented as two page tasks these JavaScript tips will get you started quickly and save you time Pragmatic Guide to JavaScript Christophe Porteneuve 150 pages ISBN 978 1934356 67 8 25 00 http pragprog com titles pg_js New Git users will learn the basic tasks needed to work with Git every day including working with remote repositories dealing with branches and tags exploring the history and fixing problems when things go wrong If youaAZre already familiar with Git this book will be your go to reference for Git commands and best practices Pragmatic Guide to Git Travis Swicegood 168 pages ISBN 978 1 93435 672 2 25 00 http pragprog com titles pg_git Pragmatic Guide to JavaScript Christophe Porteneuve Edited by Davia MeCtntock E Pragmatic Guide to Git Travis Swicegood Edited by Susannah Davidson Pfalzer K The best agile book isn t a book Agile in a Flash is a unique deck of index cards that fit neatly in your c pocket You can tape them to the wall Spread them out on your project table Get stains on them over Ag nmers ile in a Flash Speed Learning Agile lunch These cards a
97. 01 i a Charlie Says More on Profiling When we say we ship our own profiler we re actually saying Since all JVMs ship with their own basic profilers we get one for free Here sample is actually the same as passing the Xprof flag to the underlying JVM for example by using the J flag described in this chapter The stock JVM sampling profiler is a good tool of first resort for investigating bottlenecks But for large scale profiling we rec ommend either using one of the larger Java tools such as NetBeans VisualVM or Yourkit or using Ruby specific profiling libraries such as jruby prof Since JRuby is just another Java library you could pass this param eter the same way by using just the plain java binary and referencing jruby jar like this java Xmx512m jar path to jruby jar some_jruby_program rb But as soon as you try to do anything nontrivial like using the Ruby libraries that come with JRuby you ll run into path issues and have to type in even more command line options JRuby s J option offers a much better way jruby J Xmx512m some_jruby_program rb When you combine J with Java s Dname value flag you can tweak Java s many runtime parameters including the ones you read from JRuby s properties argument For example you might pass the Xdock name option to make a Swing app look a little more at home on a Mac jruby J
98. 1 0 printing January 2011 Version 2011 1 26 Cotte o Foreword by Matz 11 Foreword by Bruce Tate 12 Preface 14 Why JRUDY o dee wee e Be ee oe a ee ee 14 Whats in This BOOK i 6 scs ecet eee ee we 15 Who This Book Is For sec sad p ete do 0052 eee 16 Online RESOUrces o e s eee Sa ee a ee es 16 CONVENTIONS a s dk ee ha t Oe eee ERG REE we 17 Acknowledgments sso son gee Bh eae A ee ee 18 I JRuby Core 19 1 Getting to Know JRuby 20 1 1 Installing JRuby so sa bee ee a ee 21 12 Wicking the Tires nesese a i 4 ooo Ge es 23 13 The Interactive Shell 2 ce son soa ee 24 14 The Command Line 06 6 secs ee eee ee 24 Lo TOES 64 44 ed vd ede wa ey he 4 eee a 26 LO The Compilers lt eos e ele eh bok os es ees Ee 28 1 7 Java Integration s sso ee ee ee RR paii 29 LS Wrappime Up so raria tee kor ie Se we de 30 2 Driving Java from Ruby 31 2 1 Seeing Java Through Ruby Glasses 31 2 2 Dealing with the Classpath 38 2 0 Loading Classes s s s sos ee ee ee a aS 41 24 Using Objects 2 65 ee Pe be bee ee we wes 43 2 9 Passing Parameters 6 ck ook aa we ee 45 2 6 Calling Overloaded Methods 50 CONTENTS 2 7 Implementing a Java Interface 54 2 6 Troubleshooting gt 6 46 ood we awe ee eS 55 2 9 Wrapping Up 625 2462665 2624 2 hae ee eo 58 3 Ruby from Java Embedding JRuby 60 3 1 A Real Life Example Source Control 61 a2 The Nitty Giitty lt o ca 64 4 ade jm eee ows
99. 16 the version of Mocha that ships with JtestR contains a few tweaks to enable mocking both Java interfaces and Java classes A full catalog of these little niceties is beyond the scope of this chapter For more information see the JtestR documentation This is the short short version if you re just getting started adding Ruby tests to a Java project we strongly recommend using JtestR JUnit TestNG and Other Java Frameworks Of course there are lots of great Java testing frameworks around and in some cases you might want to supplement your chosen Ruby frame work with a few Java tests You ll usually find that you need to do a few extra steps in these situations For instance once you ve written the actual test code in Ruby you ll need to manually register your test classes with Java Most of the current Java test frameworks rely on static type annotations to find test suites and test cases This system doesn t mesh well with Ruby s dynamic classes The easiest way to reconcile the two is to write a thin Ruby wrapper around your tests The wrapper will implement a Java testing interface call the real Ruby test code and report the results back to JUnit or TestNG The JRuby project has used this technique with some success see the test directory of the JRuby source The tests are a mixture of Java and Ruby code and they use several different frameworks One overarching JUnit test suite churns through this motley collection o
100. 2 puts foo gt gt 42 The next line will not do anything since foo already has a true value foo 25 puts foo gt gt 42 The amp amp operator works much the same except that it sets the value only if the variable already exists Ruby has left shift and right shift operators that s lt lt and gt gt just like Java However these operators are quite commonly overloaded for other types to mean append Both String and Array have versions of lt lt for appending a new value Collections Ruby sports a number of useful collection classes arrays hash tables and so on Arrays are more or less like java util ArrayLists They support the same kinds of operations indexing inserting removing elements and so on Hashes are the equivalent of Java s java util HashMap They represent mappings from keys of any type to values Arrays are created with square brackets and hashes are created with curly braces Both are indexed using square brackets primes 1 3 5 seven composites 2 4 6 9 10 misc 0 Oops We should store 7 as a prime Let s fix that primes 3 7 numbers primes gt primes composites gt misc Oops We gave the wrong list for composites Let s fix that numbers composites composites You can leave off the curly braces when you re passing a hash in a method call This lets you get some of the benefits of Python style key word arguments
101. 3 exceptions 288 289 expressions vs statements 274 inheritance 276 initializers 276 loading files 289 object orientation 274 operators 284 285 optional method arguments 279 280 redefining methods 279 regular expressions 282 rest arguments 279 scope of variables 273 splatting 280 strings 281 strong typing 273 subclasses 277 symbols 282 user input 289 variable declarations 273 Ruby DL 310 RubyGems 25 RubyMine IDE 27 RUBYOPT environment variable 39 RVM Ruby Version Manager 21 C scenes Limelight 260 264 Selenium 221 223 Sequel 150 154 shebang line 297 316 Shoulda 207 211 signal callbacks 312 314 Sinatra 318 single threaded context 73 source obfuscation 81 94 splatting 280 stages Limelight 260 263 static fields 43 static method mapping 43 stories 219 220 Story Runner 218 strings 281 specify autosplit character 305 strong typing 273 stubbing see mocking and stubbing styles Limelight 261 264 267 Swing API via JRuby 241 246 via Rubeus framework 246 250 sysadmin task automation 315 316 L n test doubles 212 TEST MACROS ZENTEST test macros 209 211 test spec 205 207 Test Unit 200 202 running tests from JUnit 233 239 testing see acceptance testing integration testing unit testing web testing frameworks TextMate 26 theaters Limelight 260 thread support 72 73 Tk widget set 241 to_java 48 Tomcat 189 toStringO 64 troubl
102. 356074 240 GIS for Web Developers Adding Where to Your 2007 9780974514093 275 Web Applications Google Maps API Adding Where to Your 2006 PDF Only 83 Applications Grails A Quick Start Guide 2009 9781934356463 200 Groovy Recipes Greasing the Wheels of Java 2008 9780978739294 264 Hello Android Introducing Google s Mobile 2010 9781934356562 320 Development Platform HTML5 and CSS3 Develop with Tomorrow s 2010 9781934356685 280 Standards Today Interface Oriented Design 2006 9780976694052 240 iPad Programming A Quick Start Guide for 2010 9781934356579 248 iPhone Developers iPhone SDK Development 2009 9781934356258 576 Land the Tech Job You Love 2009 9781934356265 280 Language Implementation Patterns Create Your 2009 9781934356456 350 Own Domain Specific and General Programming Languages Learn to Program 2009 9781934356364 240 Manage It Your Guide to Modern Pragmatic 2007 9780978739249 360 Project Management Manage Your Project Portfolio Increase Your 2009 9781934356296 200 Capacity and Finish More Projects Mastering Dojo JavaScript and Ajax Tools for 2008 9781934356111 568 Great Web Experiences Metaprogramming Ruby Program Like the Ruby 2010 9781934356470 240 Pros Modular Java Creating Flexible Applications 2009 9781934356401 260 with OSGi and Spring No Fluff Just Stuff 2006 Anthology 2006 9780977616664 240 No Fluff Just Stuff 2007 Anthology 2007 9780978739287 320 Pomodoro Technique Illustrated The Easy Way 2009 9781934356
103. 500 144 to Do More in Less Time Practical Programming An Introduction to 2009 9781934356272 350 Computer Science Using Python Practices of an Agile Developer 2006 9780974514086 208 Pragmatic Guide to Git 2010 9781934356722 168 Pragmatic Guide to JavaScript 2010 9781934356678 150 Pragmatic Guide to Subversion 2010 9781934356616 150 Pragmatic Project Automation How to Build 2004 9780974514031 176 Deploy and Monitor Java Applications Continued on next page Title Year ISBN Pages Pragmatic Thinking and Learning Refactor Your 2008 9781934356050 288 Wetware Pragmatic Unit Testing in C with NUnit 2007 9780977616671 176 Pragmatic Unit Testing in Java with JUnit 2003 9780974514017 160 Pragmatic Version Control using CVS 2003 9780974514000 176 Pragmatic Version Control Using Git 2008 9781934356159 200 Pragmatic Version Control using Subversion 2006 9780977616657 248 Programming Clojure 2009 9781934356333 304 Programming Cocoa with Ruby Create 2009 9781934356197 300 Compelling Mac Apps Using RubyCocoa Programming Erlang Software fora Concurrent 2007 9781934356005 536 World Programming Groovy Dynamic Productivity for 2008 9781934356098 320 the Java Developer Programming Ruby The Pragmatic 2004 9780974514055 864 Programmers Guide Programming Ruby 1 9 The Pragmatic 2009 9781934356081 944 Programmers Guide Programming Scala Tackle Multi Core 2009 9781934356319 250 Complexity on the Java Virtual Machine Prototype and scrip
104. 6 141 142 145 146 in Swing 243 Monkeybars 250 260 monkeypatches 58 multiruby 212 MySQL 137 138 N Nailgun 298 299 name mapping 41 44 NetBeans IDE 27 250 251 number types 281 O object orientation 274 objects constructing Java objects 44 passing Java objects as parameters 47 persistent using Ribs 154 161 to_java methods 48 using Java objects 29 44 45 Oracle 136 overloaded methods 50 53 _ eea aee packaging tools 183 198 parameter passing 45 50 64 68 291 292 PDF support library 34 Playbills 261 players Limelight 260 267 268 productions Limelight 260 262 263 profiling 298 300 301 props Limelight 260 264 R Rails application structure 106 108 associations 116 117 142 components 101 103 console 117 data validation 115 142 145 database adapters 136 database configuration 109 HTTP Basic Authentication 126 installing 105 migrations 111 113 model building 111 113 115 model objects 145 146 model testing 113 115 principles 99 relations 128 129 routes 122 123 scaffolds 118 120 thread support 195 validations 142 145 views 123 126 web testing frameworks 221 228 Rake building Java programs 168 cleanup lists 172 descriptions 170 directories 168 external program calls 168 importing Ant tasks 179 integration with Ant 177 179 multitasking 171 namespaces 171 172 plug in for Maven 180 183 rules 169 tasks 166 t
105. Develop with 2010 9781934356517 300 Objective C and Cocoa Behind Closed Doors Secrets of Great 2005 9780976694021 192 Management Best of Ruby Quiz 2006 9780976694076 304 Cocoa Programming A Quick Start Guide for 2010 9781934356302 450 Developers Core Animation for Mac OS X and the iPhone 2008 9781934356104 200 Creating Compelling Dynamic User Interfaces Core Data Apple s API for Persisting Data on 2009 9781934356326 256 Mac OS X Data Crunching Solve Everyday Problems 2005 9780974514079 208 using Java Python and More Debug It Find Repair and Prevent Bugs in Your 2009 9781934356289 232 Code Design Accessible Web Sites 36 Keys to 2007 9781934356029 336 Creating Content for All Audiences and Platforms Desktop GIS Mapping the Planet with Open 2008 9781934356067 368 Source Tools Domain Driven Design Using Naked Objects 2009 9781934356449 375 Driving Technical Change Why People on Your 2010 9781934356609 200 Team Don t Act on Good Ideas and How to Convince Them They Should Enterprise Integration with Ruby 2006 9780976694069 360 Enterprise Recipes with Ruby and Rails 2008 9781934356234 416 Everyday Scripting with Ruby for Teams 2007 9780977616619 320 Testers and You ExpressionEngine 2 A Quick Start Guide 2010 9781934356524 250 From Java To Ruby Things Every Manager 2006 9780976694090 160 Should Know Continued on next page Title Year ISBN Pages FXRuby Create Lean and Mean GUIs with Ruby 2008 9781934
106. EST FRAMEWORKS lt 211 This will allow us to test the common behavior of all three Map imple mentations without repeating ourselves jruby map_shoulda rb v Loaded suite map_shoulda Started test new ConcurrentHashMap should be empty MapTestCase test new ConcurrentHashMap should raise error on entryset iterator next test new ConcurrentHashMap with one entry should associate a value with a key test new ConcurrentHashMap with one entry should have size one MapTestCase test new ConcurrentHashMap with one entry should not be empty MapTestCase test new HashMap should be empty MapTestCase test new HashMap should raise error on entryset iterator next MapTestCase test new HashMap with one entry should associate a value with a key test new HashMap with one entry should have size one MapTestCase test new HashMap with one entry should not be empty MapTestCase test new TreeMap should be empty MapTestCase test new TreeMap should raise error on entryset iterator next MapTestCase test new TreeMap with one entry should associate a value with a key test new TreeMap with one entry should have size one MapTestCase test new TreeMap with one entry should not be empty MapTestCase Finished in 1 021 seconds 15 tests 15 assertions 0 failures 0 errors Large Ruby applications use metaprogramming code that writes code to tame complexity Shoulda is a great fit for te
107. GIES Compile Mode We hesitate even to bring up this option but have decided to give it a passing mention in case you encounter it in the wild or in docu mentation In practice we strongly recommend leaving it at the default setting The compile mode determines when if ever your ScriptingContainer ob ject compiles individual Ruby methods down to JVM bytecode It is tempting to set this option to force meaning always compile After all compiling just sounds faster doesn t it Of course real life is never so simple The act of compilation takes time so it only makes sense to compile a Ruby method if it s going to be called often enough for the time savings if any to outweigh the initial delay That s exactly what the default option jit tries to do There are times when compiling Ruby code makes sense but not when you re embedding a JRuby runtime in a Java project There are a few more options beyond these basic ones You can control how an embedded JRuby runtime finds Ruby code how it finds Java classes how local variables are remembered from one invocation to the next and more Our goal however isn t to present a laundry list of every possible setting but to show you the ones you re most likely to encounter in the real world For the rest you may want to peek at the reference documentation 3 3 Embedding Strategies In our Historian example we saw several different ways to stitch the Java and Rub
108. H C path to library jar If you have both a CLASSPATH and a J cp option the latter will take priority Of course you can always combine them by referencing the environment variable from inside the search path jruby J cp CLASSPATH path to 1ibrary jar C gt jruby J cp CLASSPATH C path to library jar DEALING WITH THE CLASSPATH SN fed Charlie Says W J A Gentle Remind Make sure you have called require java before using the SCLASSPATH variable JRuby doesn t prepare that variable unless it sees you re planning to use Java libraries EN Once JRuby has loaded your program you can further manipulate the classpath from within Ruby In the Source Code As an alternative or a supplement to the command line classpath you can add a jar or directory to the CLASSPATH variable inside Ruby itself much as youre used to doing with SLOAD_PATH or for Ruby libraries Download java_from_ruby classpath rb CLASSPATH lt lt usr local lib jemmy jemmy jar To sum up what we ve seen so far in JRuby you use Java techniques to find Java code and you use Ruby techniques to find Ruby code Now we re going to do something a little different We re going to cross the language barrier and use a Ruby technique to find Java code The simplest way to do this is to use Ruby s require method to add a jar to the search path Download java_from_ruby classpath rb require usr local lib jemmy jemmy jar You
109. HitBean class definition right after the hit method Download jmx web_app rb r_attribute hits int Current hit count operation Clear the hit count returns void def clear G hits 0 end Much like Ruby s attr_reader directive makes an instance variable read able by other Ruby code r_attribute makes values readable by JMX MONITORING APPLICATIONS 318 clients In this case we want JMX to be able to see the value of the hits instance variable We re not limited to reading and writing variables The operation direc tive makes a Ruby method callable from JMX Here we ve provided a way to reset the counter to zero Once our bean has the JMX attributes and operations we want it s time to connect it to a server Download jmx web_app rb port 9999 url service jmx rmi jndi rmi localhost port jmxrmi registry RMIRegistry new port server JMX MBeanServer new connector JMX MBeanServerConnector new url server connector start bean HitBean new jruby HitBean Web app hits domain server default_domain server register_mbean bean domain type HitBean at_exit do connector stop registry stop end Now we can move on to the application we ll be monitoring The Web App After all that setup the web server itself is pretty trivial We ll use the Sinatra web framework which is great at getting projects off the ground quickly First install Sinatra jruby S gem
110. Its JRuby support is a work in progress still you might want to take a peek at http datamapper org if you like living on the bleeding edge Report erratum RUBY DATABASE FRAMEWORKS lt 135 so on Utility classes perform auxiliary tasks such as drawing graphics or parsing wire protocols Clearly model classes are what you d typi cally want to keep around in a database In the simplest incarnation of the Active Record pattern each model class is represented by one database table Each instance of that class corresponds to one row in the table and typically has one property for each column For instance a program for cataloging different species of trees might have a Tree class with name max_height and maybe a few other fields If the program follows the Active Record pattern it will keep all its trees in a trees table which might look something like this after a user enters the first couple of species id name max_height is_evergreen 1 Canyon Live Oak 30 2 2 Post Oak 15 0 In a less flexible programming language you might end up writing a lot of repetitive code to support this pattern For instance you d need a getMaxHeight method to fetch the value of the max_height column for a particular database record and convert i
111. L manually copy DLLs into Ruby s installation path and then install another Ruby library Even if they got all that right they d still encounter error messages like msvert ruby18 dll was not found Enter JRuby Its database drivers don t have to be compiled for each specific operating system and build environment so things just worked out of the box The installation procedure shrank to copy the file and then type java jar ourprogram jar What s in This Book The first half of this book is about JRuby In Chapter 1 Getting to Know JRuby on page 20 we ll hit the ground running with a few quick examples that showcase JRuby s main features In Chapter 2 Driv ing Java from Ruby on page 31 we ll show you how to call into Java libraries from Ruby code Then we ll go the other direction in Chapter 3 Ruby from Java Embedding JRuby on page 60 and extend a Java pro gram using Ruby Finally Chapter 4 The JRuby Compiler on page 78 will answer the question Isn t JRuby just a Ruby compiler for Java Short answer no In the second half we ll discuss how JRuby relates to the outside world of libraries tools and legacy code We ll start with Chapter 5 Intro duction to Rails on page 98 in which you ll build a database backed website in Ruby s most famous framework Web development leads nat urally to databases and deployment Chapter 6 JRuby and Relational Report erratum WHO THIS BOOK IS FOR
112. LEDGMENTS result of running a particular piece of code These marks are just Ruby comments JRuby ignores them and you don t need to type them But they come in handy for documenting how a function works This line doesn t print anything but the expression has a return value result 2 2 gt 4 This line prints a message when you run the program puts hello capitalize gt gt Hello This line causes an error message to appear Foo gt Uninitialized constant Foo This way we can show you what the values of different variables are in the middle of a code excerpt without having to scatter a bunch of print functions all over Acknowledgments To our initial tech reviewers Fred Daoud Steven Deobald Geoff Drake Yoko Harada Peter Lind David Rupp Vladimir Sizikov Kent Spillner and Gale Straney thank you for helping us sand down the rough edges To folks who joined the beta release process and wrote to us in the forums Matt Smith David Mitchell Arkadiy Kraportov Sam Goebert Robert Dober Pinit Asavanuchit Bharat Ruparel Hans Georg and Paul Sideleau the book is better because of your com ments and we thank you To our wonderful editor Jackie Carter thank you for being equal parts project champion product manager writing coach and cheerleader To Dave and Andy the Pragmatic Programmers thank you for giv ing this book a long runway and a chance to fly To our ever pat
113. M No matter how many ScriptingContainers you create they ll all share the same context if you use this option You can either specify this type explicitly or use the no argument form of the constructor Singleton contexts are simple to use because you don t have to pass ScriptingContainer references all around your program But they also have a big drawback they re not thread safe Try to run two chunks of Ruby code in different Java threads and kaboom Thread Safe If you know multiple threads will be accessing the same ScriptingCon tainer or if you re just feeling paranoid then you should use a THREAD SAFE context This type synchronizes all access to the Ruby runtime so that multiple threads can safely call into it without crashing This mode is certainly safer than SINGLETON but it doesn t automati cally make your concurrency problems go away Under a heavy load you may end up with a lot of waiting threads It s even possible to run into a deadlock situation For instance if an embedded script returns a Ruby object that in turn calls back into the embedding API you Report erratum THE NITTY GRITTY Tom Says 9 Even though it s a bit of extra work up front recommend start ing your project off with THREADSAFE containers This keeps you in the habit of passing around the ScriptingContainer reference in case you later decide to switch to using to one of the other two modes It also makes it harder
114. NKEYBARS lt 258 Swing list selections don t really have a single_index property But thanks to Ruby s on the fly programmability we can add one Put the following code in src swing_ext rb Download guis monkeybars src swing_ext rb java_import javax swing DefaultListModel java_import javax swing DefaultListSelectionModel class DefaultListSelectionModel def single_index get_min_selection_index end def single_index i set_selection_interval i i end end and add this line to the end of manifest rb Download guis monkeybars src manifest rb require swing_ext We ve just connected the model s and the view s notions of the currently selected chapter But what about the array of chapter names that pop ulate the list That s a separate connection Like the HTML preview this new connection needs an intermediary layer to translate between Ruby arrays and Swing DefaultListModels Download guis monkeybars src bookie bookie_view rb map view gt chapters model model gt chapters using gt list_items nil def list_items chapters items DefaultListModel new 1 upto chapters size each n items add_element n items end The trinity is nearly complete We just need to teach Bookie how to react to mouse clicks from the user This behavior will go into the controller Controller The BookieController class inside src bookie bookie_controller ro defines the controller The code generator
115. Ruby runtimes each with its own copy of the application code When a request comes in JRuby Rack selects a free runtime from the pool and hands off the request to it The net of all this is that if you need to service concurrent requests in a JRuby based Rails application you ll want to measure how much throughput you need and make a trade off between throughput and available memory Each runtime takes approximately 20MB of memory after loading the Rails framework code into it so choose your minimum and maximum number of runtimes carefully config webxml jruby min runtimes 1 config webxm jruby max runtimes 1 Another approach to concurrency is to write a thread safe application one that will run with Rails configuration threadsafe turned on and set JRuby Rack s minimum and maximum runtime values to 1 What if you want even more control over what gets put in web xml If you re comfortable with ERB Ruby s built in templating language you can modify the template that Warbler uses to generate this file Just copy WARBLER_HOME web xml erb to config web xml erb and make your edits in the copy you just created Finally what if you re using Warbler to package a hybrid Java and Ruby application If you have additional Java classes or libraries you can make sure they get packaged by setting the configjava_libs and con fig java_classes options Note that configjava_libs initially contains the JRuby and JRuby Rack jar files so b
116. S lt 115 Now let s make sure our app can recognize incomplete data We ll use the valid method to see what happens when we create a restaurant without a name Download introduction_to_rails rouge test unit restaurant_test rb def test_that_name_is_required restaurant Restaurant new assert restaurant valid end If you run this test it will fail We haven t yet told Rails that every restaurant is required to have a name To get the behavior we want and make sure that no one enters a blank name we ll need to add a validation to the model A validation is a condition that ActiveRe cord will check before saving an object to the database Objects that fail their validations don t get saved Make the following change to app models restaurant rb Download introduction_to_rails edits restaurant1 rb class Restaurant lt ActiveRecord Base validates_presence_of name end After you ve added this validation rerun the test and make sure it passes Filling Out the Roster Now that we have the Restaurant model in place it s time to add the remaining ones We can get the job done quickly by way of a shortcut in the model generator which lets us specify the columns and their types on the command line This saves us from having to edit all those migration files directly Here s what that looks like Download introduction_to_rails output script generate more models txt jruby script rails g model Administrator use
117. Says JRuby s implementation of the Ruby Array class provides a java util List interface for the Java world to use So there s really no expensive data conversion happening until some piece of Java code starts extracting individual elements from the Ruby array you passed in Download java_from_ruby array_demo rb ArrayDemo what_type_is_it a b c gt org jruby RubyArray ArrayDemo what_type_is_it a b c to_java gt Ljava lang Object JRuby can convert Ruby arrays to Java ones for you so this difference isn t much of an inconvenience in practice Plain Ol Java Objects When you ve obtained a Java object from some API call you can freely pass that object around in the Ruby world and hand it back to Java undisturbed For example let s say you wanted to construct a Java URL object stash it in a Ruby variable and then pass it into a Java method later Download java_from_ruby url_demo rb url URL new http pragprog com titles add_url_to_some_ruby_list url URLDemo retrieve_url url gt big list of book titles There s no conversion going on in this case the Java URL object is simply kept intact throughout its stay in Ruby land PASSING PARAMETERS Variable Arguments JRuby can call Java methods with variable argument lists Download java_from_ruby variable_args_demo rb VariableArgsDemo longest_string foo bazzles schnozzberry gt schnozzbe
118. Sequel ends up being a really powerful tool for working with databases What about executing arbitrary SQL Well it depends on whether you want a dataset back As we saw earlier you can use the square brackets format to do SELECTs If you want to do a raw INSERT you can do it like this Download databases sequel_insert rb require rubygems require sequel url jdbc mysq localhost 3306 using_jruby user root amp password DB Sequel connect url DB lt lt INSERT INTO blogs name author VALUESC Music _why The left shift operator is overloaded to execute any SQL statement sent to it You can also use the execute method if that feels more natural You might be worried about the lively use of datasets in these examples As it turns out the datasets in Sequel are extremely lazy meaning that they don t do anything at all until you want to get some real data out of them at which point Sequel tries really hard to do things in the database if possible So count and map will actually send out two very different SQL statements to do these operations rather than fetching an entire table into Ruby and doing the operations in memory If you want to get all the records as an array of hashes you call all on the dataset Searching in a table for a specific data item can be as simple as DB blogs id gt 1 Report this copy is P1 0 printing Janua RUBY DATABASE FRAMEWORKS lt 153 Sequel has very power
119. The main entry point that library provides is a single ant method This returns a shared instance of an Ant object through which we can invoke Ant tasks Here s how you d invoke Ant s built in echo task Note the use of a Hash to pass parameters into the task Report erratum Nick Says JRuby does not ship with Ant you still need to have it installed separately JRuby will detect where Ant is installed by attempt ing to invoke the ant program so make sure it s installed and available on your PATH Modern versions of Mac OS X come with Ant preinstalled and Ant is available on many flavors of Linux through your distribution s package manager On Win dows you ll probably have to still download and install Ant and make sure the ant executable is on the PATH Download rake ant examples echo rb require ant ant echo message gt Hello from Ruby The ant method also accepts a block so you can run multiple tasks conveniently Download rake ant examples setup rb require ant ant do echo message gt Setting up new project echo message gt Project description goes here file gt README txt mkdir dir gt Jib mkdir dir gt test end If the Ant task uses nested elements simply use nested blocks Download rake ant examples javac rb require ant ant javac srcdir gt src destdir gt build do classpath do fileset dir gt Jib do include name gt jar end
120. The model contains the business logic and data this may include connecting to a database The controller is responsible for providing the view with all the data needed for the current interaction with the user It also responds to user actions by evaluating them and dispatching to a model A controller should be small think of it as the switch board between the models and the views The view displays data in different formats Rails apps often implement this layer using eRuby a mix of Ruby and HTML These are the central parts of Rails everything else is just the plumbing necessary to make everything work In Rails your models are usually ActiveRecord classes see Sec tion 6 1 ActiveRecord on page 134 kept in app models The views are usually html erb xml erb or js rjs files and they live in app views Finally the controllers are regular Ruby classes that are placed in app controllers This division makes it very easy to know where code should be placed and what the responsibil ity of each piece is Report erratum is P1 0 printing January 2011 WHAT IS RAILS Agile Though Agile is of course a general computer industry buzzword it has specific connotations in Rails With the Ruby language you can get off the ground quickly with clear understated code With built in test harnesses you can safely change directions in the middle of a project It s all about bringing more value to your appli cation in less
121. Their details belong firmly in the things needed only by the maintainers of Test Unit category so just gloss over the gnarly bits and focus on the class names Download beyond_unit_tests junit_integration test_unit_junit rb class JUnitAdapter private def collect_all_test_unit_classes proc do runner c TestUnitClassCollector new c filter runner filters c collect Tests test_unit_classes end end def report_results_to_junit proc do runner TestUnitResultHandler instance_variable_set result_handler test_result TestUnitResultHandler end end def test_unit_classes all ObjectSpace each_object Class do klass if Test Unit TestCase gt klass all lt lt klass end end all end end This code references two new classes we ll need to define TestUnitClass Collector and TestUnitResultHandler First let s look at the collector Its job this copy is P1 0 printing PLUGGING INTO JAVA lt d 236 is to collect a bunch of separate Ruby classes into a single test suite Test Unit calls into it before running the tests Alas the details are a piece of necessary but uninteresting boilerplate Download beyond_unit_tests junit_integration test_unit_junit rb class TestUnitClassCollector include Test Unit Collector def collect name klasses suite Test Unit TestSuite new name sub_suites klasses each do klass add_suite sub_suites klass suite end sort sub_suites each s s
122. Thomas Dave Thomas with Chad Fowler and Andy Hunt 992 pages ISBN 978 1 9343560 8 1 49 95 F The Facets SARE of Ruby Series http pragprog com titles ruby3 Rails just keeps on changing Rails 3 and Ruby 1 9 Bs bring hundreds of improvements including new eae N APIs and substantial performance enhancements The fourth edition of this award winning classic i aA ileWeb has been reorganized and refocused so it s more evelopment useful than ever before for developers new to Ruby with liS muam and Rails This book isn t just a rework it s a complete refactoring Agile Web Development with Rails Fourth Edition Sam Ruby Dave Thomas and David Heinemeier PR kd Hansson et al eia Aaa Cece oe nes n 500 pages ISBN 978 1 93435 654 8 43 95 http pragprog com titles rails4 More Languages ven Lan in Seven Week In this book you ll get a hands on tour of Clojure Haskell Io Prolog Scala Erlang and Ruby Whether or not your favorite language is on that list you ll broaden your perspective of programming by examining these languages side by side You ll learn something new from each and best of all you ll learn how to learn a language quickly Seven Languages in Seven Weeks A Pragmatic Guide to Learning Programming Languages Bruce A Tate 300 pages ISBN 978 1934356 59 3 34 95 http pragprog com titles btlang L Antipattern If you re programming applications that store data t
123. Y_AXIS frame add split_pane frame add button frame visible true The frame uses a layout manager Swing s way of specifying where con trols will appear relative to one another both initially and when the window is resized Layout managers are a rich topic in their own right and worth reading up on if you plan on doing a lot of Swing work There we have it In the worst case scenario of using raw Swing without the help of any Ruby frameworks we spent about 60 lines of code Not too bad actually You could add another 60 lines to deal with loading saving and printing documents But before you go write the next great text editor let s look at some JRuby based GUI frameworks built on top of Swing Maybe we ll find ways to remove some of the Swing esoterica from our top level GUI code Rubeus Rubeus is a GUI framework whose developers think that completely eliminating the details of Swing may not be possible No matter how good an abstract framework is some of Swing s details will leak into your code With that in mind they decided to concentrate on removing the worst of Swing s pain points without ever hiding the fact that you re still coding to the Swing API You can think of Rubeus as Swing with a Ruby friendly syntax This pragmatic approach has a few advantages e You can still read Swing documentation and training materials and apply what you ve learned to your Rubeus project 5 http code google com p r
124. You can define multiple mappings if you want to for instance you could have one for each database or let models inherit definitions and mappings from one other These are quite advanced features though and beyond the scope of this chapter There are many more things you can do with Ribs and there are also a couple of interesting alternatives on the horizon if you need behavior that Ribs doesn t provide But this introduction should at least make it possible for you to start using Ribs to persist your Ruby objects JDBC We ve covered a lot of Ruby database libraries plus one Java persis tence framework that play well with JRuby How about other Java libraries In many cases you can just fall back on familiar Ruby to Java method calls Say you wanted to work with something like iBatis for instance It would be simple to use the techniques from Chapter 2 Driving Java from Ruby on page 31 to call your generated iBatis objects just like any other Java object Sometimes though you just want to go straight to the database and do one or two queries without the overhead of a big framework Thanks to JRuby s outstanding Java integration support you can work directly with JDBC from your Ruby code Even without the benefit of abstrac tion the code ends up being a bit more tasteful than its Java equivalent would be 14 http github com headius jibernate Report erratum To get a simple connection running with JDBC y
125. _border_color default_background_color center width 22 height 8 rounded_corner_radius 4 secondary_background_color fOfOf0 gradient on gradient_angle 270 border_width 1 left_margin 4 padding 4 7 is P1 0 print APPENDIX F LIMELIGHT EXAMPLE SOURCE lt 325 tabs width 100 height 10 horizontal_alignment center tab_button extends default_border_color default_background_color horizontal_alignment center vertical_alignment center secondary_background_color fOfOfoO gradient on gradient_angle 270 padding 5 hover secondary_background_color sky_blue tabs_holder extends fill_parent float on y 15 x 37 j tabs_shadow extends default_border_color extends fill_parent top_margin 50 left_margin 8 right_margin 8 top_border_width 1 left_border_width 1 right_border_width 1 background_color fOf0Of0 left_tab top_left_rounded_corner_radius 4 bottom_left_rounded_corner_radius 4 border_width 1 right_tab top_right_rounded_corner_radius 4 top_right_border_width 1 bottom_right_rounded_corner_radius 4 bottom_right_border_width 1 left_border_width 0 APPENDIX F LIMELIGHT EXAMPLE SOURCE lt 326 right_border_width 1 top_border_width 1 bottom_border_width 1 preview_pane extends default_border_color default_background_color width 100 height 90 left_border_width 1 right_border_width 1 bottom_border_
126. a copy so we don t modify the original array copy clone block call copy factorial 1 times do copy permute block call copy end end end For each iteration we permute the array once using an algorithm from Dijkstra s The Problem of the Next Permutation Dij76 Download compiler jit permute rb class Array Generate one permutation by Dijkstra s algorithm def permute i length 1 i 1 while at i 1 gt at i j length j 1 while at j 1 lt ati 1 swap i 1 j 1 i 1 j length while i lt j swap i 1 j 1 i 1 j 1 end end def swap a b self a self b self b self a end end this copy is P1 0 printing Jc COMPILER 101 Here are the results of running the benchmark Download compiler sessions jit txt jruby permute rb 0 381000 0 000000 0 381000 0 255000 0 117000 0 000000 0 117000 0 117000 0 017000 0 000000 0 017000 0 017000 0 017000 0 000000 0 017000 0 017000 0 010000 0 000000 0 010000 0 011000 You can immediately see one very noticeable result the numbers get faster over time Where the initial run takes around 0 255s of real time the subsequent runs take anywhere from 0 011s to 0 117s What you are seeing is the effect of JRuby s JIT and the JVM s JIT too compiling code as it runs to improve performance Getting the Best Out of JIT Most JRuby users will never need to think about the JIT It will run qui etl
127. a safe one is well unsafe But don t let that frighten you too much Sometimes C gives you exactly the direct hardware access high performance or software interoperability you need this copy is P1 0 printing Appendix E Ruby for Svsadmin We have talked a lot about developing applications and libraries with JRuby What about other tasks such as administering a system It turns out that JRuby is a great fit for running a single computer or an entire network You get the benefits of Ruby s quick scripting abilities and Java s monitoring libraries There s enough material on scripting your system with Ruby to fill an entire book In fact such a book already exists But we couldn t resist bringing up the subject here too Automating Tasks Ruby has a long history of helping sysadmins get their jobs done It s no secret that Perl the duct tape that holds networks together all over the world was a big inspiration for Ruby Several of Ruby s idioms came straight from Perl the most famous of these is regular expression matching You can use JRuby in the same kinds of situations where you d use shell scripts batch files or Perl programs For instance let s say you re running a UNIX system where the corporate policy is that the company name has to be in everyone s email signature file 1 Everyday Scripting with Ruby MarO6 by Brian Marick 2 That doesn t sound like a place we d like to work Bu
128. actory method for our Person class Download ruby_101 class_method rb class Person def self with_address_and_phone_number addr ph p Person new p add_address addr p add_phone_number ph p end end The following can appear between class Person and end or it can stand alone outside the class definition def Person with_address_and_phone_number addr ph end As you can see this looks just like a static method But really it s just a regular method Instead of belonging to an individual Person it belongs to the Person class Remember classes are objects too that means they can have methods attached to them While we re on the subject of method definition note that you can rede fine methods in Ruby if you want Both of the previous definitions could be placed in the same program and Ruby wouldn t complain You can also modify class definitions For instance you could have multiple class Person end sections in your program even some that might or might not execute based on a runtime condition That isn t something you d do in a typical program but it can be a big help if you re trying to extend Ruby itself Method Arguments Ruby methods can take zero or more arguments Instead of overload ing methods Ruby allows methods to take optional arguments with a default value You can also create methods that take an arbitrary number of arguments An argument like that is usually c
129. add You can take this code as documentation mind set one step further and use this copy is P1 0 printing lt q 204 RUBY TEST FRAMEWORKS lt 205 the fs flag to document the entire specification rather than just the failed or pending steps jruby S rspec fs hashmap_spec rb An empty Java JavaUtil HashMap should be empty should have size zero should allow elements to be added PENDING Not Yet Implemented Pending An empty Java JavaUtil HashMap should allow elements to be added Not Yet Implemented hashmap_spec rb 18 Finished in 0 13 seconds 3 examples O failures 1 pending Examples and expectations are the core of RSpec Even using just these two features will bring a lot of clarity to your tests Once you re com fortable you ll likely want to explore its more advanced features Later in the chapter we ll look at one such feature support for mock objects But first there are a couple more unit test framework we d like you to see test spec The test spec framework combines the simplicity of Test Unit with the clear syntax of RSpec So you can use your existing knowledge of Test Unit while adopting the advantages of BDD at a pace you choose To try these examples install the test soec gem note the hyphen jruby S gem install test spec Using test spec our HashMap example would look like this Download testing_with_jruby test_unit hashmap_test_spec rb require rubygems
130. ady seen how to create a Rake task to compile this Java code Download rake scrape Rakefile desc Build Java launcher that will start the Ruby program task build_launcher do sh javac cp jruby complete jar Launcher java end Now we just combine the newly built class file our Ruby program and the Hpricot library into a jar Download rake scrape Rakefile desc Combine app and launcher into one jar task small_jar gt install_gems build_launcher do sh jar cfm scrape jar small manifest Launcher class scrape rb C vendor end The task requires a new file small manifest This is where we provide startup information which Java uses to find the Launcher class and the supporting JRuby libraries Download rake scrape small manifest Manifest Version 1 0 Class Path jruby complete jar Main Class Launcher With that addition we can build the jar file jruby S rake small_jar Once that s done you can run the program You ll need a copy of jruby completejar in the same directory java jar scrape jar Cocoa Programming is at http pragprog com titles dscpq cocoa programming ExpressionEngine 2 is at http pragprog com titles riexen expressionengine 2 Hello Android is at http pragprog com titles eband3 hello android iPad Programming is at http pragprog com titles sfipad ipad programming SQL Antipatterns is at http pragprog com titles bksqla sql antipatterns The RSpec Book is at http pragprog
131. age on the robust and reliable JVM and we ve come full cir cle Now I m writing a foreword for Thomas and Charles and I could not be more thrilled You see the last missing piece of the JRuby puzzle is effective documentation That s where Using JRuby steps in This book tells the perfect story at the right time This team of authors is uniquely positioned to give you the tips and tricks from the inside They ve nur tured this project from its infancy to where it is today They ve used JRuby to deliver real value to paying customers And they re gifted com municators who can effectively tell this story I ve been waiting for this day for a long time and I could not recom mend this book more highly Congratulations Charles Thomas Nick Ola and Ian You ve created something amazing and described it in a beautiful book Bruce Tate Author From Java to Ruby 2006 Austin Texas 2010 Report erratum this copy is P1 0 printing January 2011 Preface You know all the stereotypes of the Java and Ruby programming lan guages The enterprise vs the upstart The staid corporate safe choice against the free wheeling new kid in town Look a little deeper though at what the languages have in common They re about the same age both had their 1 0 releases in 1996 Both their respective inventors were inspired by their favorite object oriented language features And both Java and Ruby have touched off an ava lanche of I
132. ails application is now ready to start Download introduction_to_rails output script server txt jruby script rails server gt Booting WEBrick gt Rails 3 0 1 application starting in development on http 0 0 0 0 3000 gt Call with d to detach gt Ctrl C to shutdown server 2010 10 15 11 08 40 INFO WEBrick 1 3 1 2010 10 15 11 08 40 INFO ruby 1 8 7 2010 10 13 java 2010 10 15 11 08 40 INFO WEBrick HTTPServer start pid 6137 port 3000 You should be able to visit hitp localhost 3000 and see the standard Rails welcome page Building Our Models Now that we know Rails works correctly and your application is config ured as it should be it s time to sketch out our models You re probably not surprised to hear we ll be using Rails code generation again That First Step Is a Doozy You will see several things get generated in the following interaction These include a nearly empty Ruby file containing your model and another Ruby file called a migration Rails won t actually put anything in the database for you until you specifically ask it to do so The migra tion defines exactly what gets added Download introduction_to_rails output script generate model txt jruby script rails generate model Restaurant invoke active_record create db migrate 20101014180911_create_restaurants rb create app models restaurant rb invoke test_unit create test unit restaurant_test rb create test fixtures restaurants yml As
133. ake style FileLists config includes lt lt some extra file you need config excludes FileList Jib super_private The next area you might want to customize is the set of extra gems that Warbler should include in case Warbler s discovery process missed one config gems provides several different ways to specify gems to include config gems activerecord jdbcmysql adapter jruby openss config gems rai7ls 2 3 5 config gems lt lt Gem Dependency new json_pure gt 1 4 0 Warbler usually packages all gems into an embedded gem repository located at WEB INF gems inside the war file If instead you ve vendored copied your app s required gems into your application s directory tree you can just tell Warbler to use the appropriate path config gem_path WEB INF vendor gems As we saw in the previous section Warbler tries to autodetect what kind of application you are packaging so that it can set up some reasonable defaults If you don t want Warbler to do that there s a line at the top of config warble ro that you can uncomment to turn the detection off Disable automatic framework detection by uncommenting setting to false Warbler framework_detection false Just be warned that if you ve turned framework detection off you re probably going to have to specify more details manually in Warbler s configuration One of those details is the name of the launcher Warbler should use
134. alled a rest argument Regular arguments are separated by commas as you ve already seen To create a method that takes optional arguments you use the equal sign Report erratum A CLOSER LOOK lt 280 def you_gave_me present nil present end you_gave_me gt nil you_gave_me a pony gt a pony This method takes one optional argument If the argument is not sup plied present will contain nil You can have several optional arguments and even default values that are calculated In the following example we use the first argument to calculate the default value for the second one def area width 10 height 2 width width height end area gt 200 area 5 gt 50 area 5 20 gt 100 Ruby also has a way of taking an arbitrary amount of arguments like Java s varargs You define a rest argument using the asterisk def quote person words person says words join end quote Ola gt Ola says we quote Ola keep coding gt Ola says keep coding As you can see the asterisk takes all the remaining arguments and squishes them into an array called words The asterisk can also perform the opposite action expanding an array into individual arguments for a method Consider the following function that requires three arguments def something needs three arguments Yay end my_array one two three something my_array
135. ands as much in Sequel as you do in DBI The goal for Sequel was to layer a Ruby like interface over some of the cases that ActiveRecord didn t handle so well in the past such as large data sets Sequel also includes model and migration features similar to those of ActiveRecord albeit more integrated with the rest of the library than their ActiveRecord counterparts Before we start looking at some examples of Sequel it s important to know that not everything that looks like familiar Ruby will actually be 9 http ruby dbi rubyforge org Report erratum RUBY DATABASE FRAMEWORKS lt 151 executed as it reads There are some circumstances where Sequel does exceedingly clever things with Ruby code such as transforming it into SQL for later execution in the database This can cause some of the examples to look a bit unusual To be able to use Sequel you just need to install the sequel gem jruby S gem install sequel Now you can use something like this to take a look at the database Download databases sequel_simple rb require rubygems require sequel url jdbc mysq1 localhost 3306 using_jruby user root amp password DB Sequel connect url DB blogs each do row p row end Each row comes back as a Ruby Hash jruby sequel_simple rb id gt 1 name gt Languages author gt Ola Bini id gt 2 name gt Politics author gt Roy Singham id gt 3 name gt Environment
136. ants do restaurants restaurants hashes each do r visit new_restaurant_path fill_in restaurant name with gt r name click_button Create end end Those three lines in the middle are Webrat calls See how fluidly it reads Visit this URL Fill in this field Click this button Let s go through those line by line We could have written the URL directly as visit restaurants new But our code will be a little more future proof if we use new_restaurant_path a name that Rails defined for us while we were building Rouge Webrat identifies the text field to fill in by its name property In other words this code is expecting to see a chunk of HTML that looks some thing like lt text name restaurant name gt Similarly the call to click_button looks for a submit button whose value is Create To check the results we go back to the list of restaurants and make sure the newly added one shows up 4 In The RSpec Book CAD 09 David Chelimsky refers to this technique as Direct Model Access Report erratum ACCEPTANCE TESTING Download introduction_to_rails rouge features step_definitions restaurant_steps rb Then AI should see the following restaurants do expected visit restaurants_path actual table tableish table nth of type 2 tr td th actual map_headers h h downcase expected diff actual end Just like the other two steps this one takes a table as input in t
137. are several extremely good testing frameworks in Ruby have personally tried unit testing in most of the popular programming languages and can testify that Ruby frameworks are without doubt the best In Ruby big picture innovations like Behavior Driven Develop ment rapidly become frameworks that are practical for every day development don t know why Ruby is the language where many of these things happen but it might have some thing to do with the way Ruby programmers naturally seem to embrace metaprogramming and other techniques that take testing to the next level RUBY TEST FRAMEWORKS lt 200 If you re specifically interested in testing Java code with Ruby you might find the JtestR framework helpful JtestR collects several Ruby frameworks together for use with JRuby and makes the integration with Ant or Maven totally painless JtestR is described in detail in Sec tion 9 3 JtestR on page 229 Until then we ll consider each test frame work separately Let s begin with a couple of the more popular tools for organizing and running tests 8 1 Ruby Test Frameworks Using JRuby to test Java code is one of the easier ways to get started with JRuby If you start small and focus on testing you can overcome the institutional resistance to Ruby present in some shops After all it s hard for colleagues to object to a quick experiment that s going to be limited to the test suite especially if the potential payoff
138. as ASCII art Table driven testing is a tremendously expressive way to show several exam ples in a compact space How does Cucumber pass that chunk of tabular data into your test code It constructs an instance of a class called Cucumber Ast Table which provides several convenient methods for getting at the informa tion inside Let s see how to use one of these methods Put the following code into a file called features step_definitions restaurant_steps rb Download introduction_to_rails rouge features step_definitions restaurant_steps rb Given Athe following restaurants do restaurants Restaurant create restaurants hashes end this copy is P1 0 printing Jal ACCEPTANCE TESTING lt 226 The table s hashes method returns the cells of the table converted to an array of Hash objects name gt Kenny and Zuke s name gt Horse Brass Pub By a lovely coincidence this happens to be the same format that Active Record s create method takes Yes we re creating the database record directly behind the scenes rather than going through the GUI You wouldn t want to do this in the heart of the test the When and Then steps where we re actually checking the GUI But it s sometimes OK during the Given step which is really just the setup Now we can move on to the When step Download introduction_to_rails rouge features step_definitions restaurant_steps rb When AI add the following restaur
139. ass WaveformWrapper static ScriptingContainer rubyContainer Object waveform static rubyContainer new ScriptingContainer rubyContainer runScriptlet require waveform public Waveformwrapper double points Object waveformClass rubyContainer runScriptlet Waveform waveform rubyContainer callMethod waveformClass new points public double rms return Double rubyContainer callMethod waveform rms A SIMPLE COMPILED EXAMPLE This code requires you to have a definition of the Waveform Ruby class sitting around either in waveform rb or in waveform class What if you want all the waveform related code in a single class file The simplest way to do that is just embed the Ruby code straight in the java file by replacing the static section with something like this Download compiler waveform WaveformComplete java static String source new StringBui lder class Waveform n def initialize points n points points n end n n def rms n raise No points unless points length gt O n squares points map p p p n j sum squares inject s p s p n mean sum squares length n j Math sqrt mean n end n end n toString rubyContainer new ScriptingContainer rubyContainer runScriptlet source The advantage of this approach is that it s simple and reliable The disadvantage is that it takes a lot
140. assed into our mock Map Some situations may call for more exactness Both RSpec and its competitors have various constraints you can apply to passed in arguments 7 http rspec info documentation mocks message_expectations html this copy is P1 0 printing MOCKING AND STUBBING lt 216 RSpec mocks are available everywhere you can write examples They re also available in Cucumber step definitions which are described in Sec tion 9 1 Writing High Level Tests with Cucumber on page 218 but this use is less common The mocking techniques we have seen so far rely on Java interfaces RSpec isn t able to add mock implementations to a concrete Java class For that we ll need to turn to another mocking tool Mocha Mocha is one of the top Ruby mocking stubbing frameworks designed to work in several different testing frameworks including most of the ones we ve seen so far Its API is less chatty than RSpec s for example expects instead of should_receive but still reads somewhat like English Let s see how the previous example would look with Mocha First we need to install the framework jruby S gem install mocha Second we need to configure RSpec to use Mocha The following code can go before or after the java_import directives from last time Download testing_with_jruby mocha hashmap_spec rb require mocha RSpec configure do config config mock_with mocha end Finally we can use Mocha style
141. atum PASSING PARAMETERS We re as mistrustful of magical thinking in programming as you are Fortunately there s no magic here just some straightforward mappings between Java and Ruby types Once you understand why and how JRuby selects methods and converts parameters you ll always know how your code will behave Simple Type Conversion For meat and potatoes types like numbers and strings JRuby will copy each Ruby parameter into a reasonable Java equivalent Consider this Java class Download java_from_ruby BigIntDemo java import java math BigInteger public class BigIntDemo public static final BigInteger GOOGOL new BigInteger 10 pow 100 public static boolean biggerThanGoogol BigInteger i return GOOGOL compareTo i lt 0 I and the Ruby code that calls it Download java_from_ruby big_int_demo rb a_big_number 10 100 1 BigIntDemo bigger_than_googol a_big_number gt true Ruby s Bignum class and Java s java math Biginteger are distinct types but JRuby seamlessly converts the Ruby data into its Java counterpart Arrays Although JRuby adds a few conveniences to Java arrays to make them feel a little more at home in the Ruby world Ruby arrays and Java arrays are actually distinct types Download java_from_ruby ArrayDemo java public class ArrayDemo public static String whatTypeIsIt Object o return o getClass getNameQ PASSING PARAMETERS a Charlie
142. author gt Al Gore id gt 4 name gt Architecture author gt Richard Gabriel id gt 5 name gt Physics author gt Lee Smolin id gt 6 name gt Memes author gt Richard Dawkins Note that we specify the connection information just like we would when connecting to JDBC That s because JDBC is actually used under the covers so this is really a JDBC URL Once we have a connection there are lots of ways of getting data out of it The shortcut used in this code allows us to get a dataset that points to a specific table DB blogs is more or less a shorter way of saying DB select from blogs Sequel includes quite a lot of clever shortcuts like this The goal is to allow you to write Ruby code for most things where you would have needed SQL in other frameworks Once you have a dataset you can do some clever things with it Say you want to get aggregate information such as a count or maybe you re just interested in a specific entry RUBY DATABASE FRAMEWORKS lt 152 Download databases sequel_functions rb require rubygems require sequel url jdbc mysq1 localhost 3306 using_jruby user root amp password DB Sequel connect url p DB blogs count p DB blogs map C name jruby sequel_functions rb gt Languages Politics Environment Architecture Physics Memes There are a huge amount of these simplifying methods all over Sequel Once you master them
143. bcdbf adapter 0 9 7 2 java activerecord jdbcderby adapter 1 0 2 java 0 9 2 activerecord jdbch2 adapter 1 0 2 java 0 9 2 activerecord jdbchsqldb adapter 1 0 2 java 0 9 2 activerecord jdbcmssql adapter 1 0 2 java activerecord jdbcmysql adapter 1 0 2 java 0 9 2 activerecord jdbcpostgresql adapter 1 0 2 java 0 9 2 activerecord jdbcsqlite3 adapter 1 0 2 java 0 9 2 and then install the driver for your database For example if you were using MySQL you d type this jruby S gem install activerecord jdbcmysql adapter If you re using a commercial database like Oracle or Microsoft SQL Server you ll also need to download your vendor s JDBC driver and copy it into JRuby s lib directory For example with Oracle 10g you d look for ojdbc14 jar on the official download site For the most part your Ruby code will look the same whether you use the generic driver or a specific one We ll note the few places where you need to do something different between the two 2 http www oracle com technetwork database enterprise edition jdbc 10201 08821 1 html this copy is P1 0 printing RUBY DATABASE FRAMEWORKS Once you have chosen and installed your database adapter you can finally install ActiveRecord itself jruby S gem install activerecord At this point it s a good idea to check that everything is working by connecting to a database and executing some raw SQL Here s how you d do that using the gen
144. bookie_model rb E Internal Frame S Layered Pane 8 bookie_view rb gt E org rubyforge rawr UFrame Properties ceo gt Ubraries Properties Binding Events Code w Properties jefaultCloseOperationEXIT_ON_CLOSE itle i a Form Bookie mice 28 w Other Properties gt amp Other Components lwaysOnTop o gt E UFrame background O 238 238 238 cursor Default Cursor nabled iextendedState 0 ocusCycleRoot M ocusTraversalPolicy lt default gt ocusTraversalPolicyPro ne ocusable mM aly UFrame Figure 10 2 The Matisse GUI editor A almost the entire rectangle leaving only a thin strip along the bottom big enough for a button As you do this notice that Matisse helps you snap the component to the nearest edge of the window At this point you have two huge buttons with a splitter between them Don t panic the buttons are just placeholders which we ll soon fill in with real controls The first of these will be the chapter list Drag a List from the palette onto the left button Matisse will replace the button with the new control Filling in the other half of the layout follows a similar process Drag a Tabbed Pane onto the right button It won t have any tabs at first these will get created automatically as you drag controls into the middle of it Go ahead and do that now You ll nee
145. but different trade offs For instance Celerity is geared toward Javascript heavy pages Capybara supports several browser back ends but leaves out some features in the name of portability If you like this style of API but need some thing specific that Webrat doesn t offer you may want to take a look at one of these other toolkits x http celerity rubyforge org t http github com jnicklas capybara Then install the JSSh plug in for Firefox which adds the testability hooks that Watir uses Once that s done you can run the Cucumber story the same as before Now that we ve seen two different libraries that drive a live browser let s look at a different approach talking directly to a web application from Ruby Webrat Webrat is a Ruby library that provides a simple API for web testing With it you write calls like visit_link blog new or click_button Create to drive your site In addition to making tests easy to write Webrat aims to make them easy to run Your test code will call straight into your application code as long as it s written in one of the Ruby frameworks Webrat knows about Not only do you not need a web browser but you don t even need to launch your application in a web server Let s see what one test case might look like in Webrat Since we need a Ruby app to test let s use the Rouge restaurant guide from Chapter 5 1 http wiki openga org display WTR FireWati
146. by has while loops like Java does It also has a for loop but you ll almost never see it in real programs Instead Ruby offers something much more powerful blocks Blocks Blocks are a huge part of Ruby Basically they re little chunks of code that you can pass around your program as arguments You define them by wrapping some code in curly braces or the words do and end Most people prefer braces for single line blocks and do end for multiline blocks but use your own judgment list 1 2 35 4 list each n puts n list each do n puts n end This code calls an Array method called each this method takes a block each calls the block also known as yielding to it once for each item in the array Like functions blocks can take arguments That s the n you see in between pipe characters It s easy to write your own method that takes a block You can either explicitly name the final argument as a block by spelling it with a lead ing ampersand or just call yield from within your method def yield_thrice value yield value 10 yield value 20 yield value 30 end def call_thrice value amp block block call value 10 block call value 20 block call value 30 end Report this copy is P1 0 printing Janua A CLOSER LOOK lt 4 288 Both of these will print the numbers 110 120 and 130 yield_thrice 100 n puts n call_thrice 100 n puts n Every time the method yields to
147. c Rake tasks can perform any actions that you find useful even things unrelated to building software Rails uses Rake for all kinds of house keeping populating databases running tests launching web servers and so on To run a task pass its name to rake on the command line Download rake sessions rake_sandwich txt jruby S rake sandwich Cin code rake sandwich Slicing the bread Grating the cheese Grilling the sandwich If the Rakefile has a task called default Download rake sandwich Rakefile task default gt sandwich then you can invoke it by running rake with no arguments Like Ant and Make Rake will run all of a task s dependencies first You can see this for yourself by invoking Rake with the trace option Download rake sessions rake_trace txt jruby S rake trace Cin code rake sandwich Invoke default first_time Invoke sandwich first_time x Invoke bread first_time Execute bread Slicing the bread x Invoke cheese first_time x Execute cheese Grating the cheese Execute sandwich Grilling the sandwich x Execute default Here you can see how Rake looks for the default task finds and runs its prerequesities and then ends up back in default this copy is P1 0 printing Making sandwiches is all well and good but what does that have to do with Java Let s look at something more pertinent using Rake to build a Java program Files and Processes Consi
148. c coverage of the API What Is Rails Rails is a web application framework It has seen great success in the past few years because of several revolutionary differences from earlier web frameworks It has given countless developers the tools to create web applications in an easy and intuitive way Rails removes the need for giant configuration files gives you a set of reasonable defaults uses Ruby s expressiveness to keep your code readable and focuses on mak ing the most common use cases dead simple When you combine the rapid development of Rails and the power of the JVM you can do the following e Handle an entire site s worth of traffic in a single Rails instance thanks to Java s multithreading WHAT IS RAILS Connect to a huge range of legacy databases without struggling with native database drivers Use one of Java s many libraries for persistence messaging or image processing from your Rails app Deploy clean compact Ruby code to a Java only server environment Wrap a web interface around a legacy application such as the Tracker 7 software that s keeping the world safe from nuclear proliferation Principles Although the success of Rails can be credited to the way it changed how we build web applications Rails is also distinguished by brilliant marketing including the propagation of several slogans and buzzwords Here are a few of the more common slogans together with their mean ings in the contex
149. code is an excerpt from the props rb file we saw a moment ago stripped down to just the structure of the tabs tabs do tabs_shadow tabs_holder do tab_button Edit button tab_button Preview button end edit_pane preview_pane end Compare this code with Figure 10 5 Each object corresponds to a graphical element in the screenshot Most of these connections are obvious but what about tabs and tabs_holder Well tabs is just the this copy is P1 0 printing Janua LIMELIGHT lt 266 whole screenshot tabs_holder is a container that wraps the two tab but tons We ve added this prop to make layout easier Let s look at its style code Download guis limelight bookie bookie styles rb tabs_holder extends fill_parent float on y 715 x 37 F This is one of the more intricate styles in the project so we ll go over it line by line Starting at the bottom and working our way up we see a relative x and y position that will keep the buttons nicely centered no matter the window size The next line up float on resembles the CSS property of the same name It allows the tab holder to overlap other controls Here we want to overlap the tab shadow to make the entire section look like a cohesive unit Finally we come to extends fill parent This notation is Limelight s way of sharing common styles Several of Bookie s props need to expand to fill their containers So we ve defined a common fill_parent style a
150. com titles achbd the rspec book Now all you have to do to share your program with someone is hand them these two jar files and tell them what command to run But why deliver two files when we can deliver one this copy is P1 0 printing PACKAGING FOR DEPLOYMENT lt 187 One Big Jar All we have to do to combine the two jars into one is extract JRuby into a temporary directory Download rake scrape Rakefile directory tmp desc Extract jruby complete so we can combine it with the app task extract_jruby gt tmp do Dir chdir tmp do sh jar xf jruby complete jar end end and rerun the jar command telling it to include the new path as well Download rake scrape Rakefile desc Combine app launcher and JRuby into one jar task big_jar gt install_gems build_launcher extract_jruby do sh jar cfm scrape jar big manifest Launcher class scrape rb C vendor C tmp end Since we re just using one jar now the manifest is even simpler than the previous one Download rake scrape big manifest Manifest Version 1 0 Class Path Main Class Launcher And that s it One deliverable jar file containing your app and every thing it needs If you need to repeat this procedure from project to project you may be interested in the Rawr library which automates some of these tasks Creating Web Archives with Warbler Now that you have an inkling of how a Ruby application can be easily
151. compressed You re left with just the parts you need to read in order to understand what failed autotest makes continuous testing easy If you follow a few simple nam ing conventions it will figure out which tests it needs to run for each file Every time you save a modification to your class autotest will run the corresponding tests This smoothes your workflow dramatically you can continue coding functionality with the assurance that you will be notified as soon as something fails multiruby allows you to run code against multiple Ruby implementa tions including JRuby This capability is a life saver for library writers who must wrestle with compatibility across some ten different Ruby implementations All of these tools are documented on Ryan Davis s blog We encourage you to give them a try once you have a growing body of test code to maintain Now we re going to move on to one more crucial facet of unit testing test doubles 8 3 Mocking and Stubbing In most projects you ll eventually end up needing to test code that relies on external libraries or services Your unit tests should minimize 5 http blog zenspider com Report erratum 1 0 printing January 2011 MOCKING AND STUBBING lt 213 Sa bt lan Says Mocks vs Stubs What s the difference between mocks and stubs They can both be used in place of a real object but mocks are pick ier they care how they re called Therefore only
152. course just copy those same two lines to any project s Rakefile yourself but it s nice that Warbler offers this convenient short cut The function of Warbler Task new is to define several Rake tasks to per form the packaging work Of these Warbler s main task is the war task If you have other work to do before packaging up your war file you can make the war task depend on your other tasks this copy is P1 0 printing Jai PACKAGING FOR DEPLOYMENT As an example the popular asset_packager plug in creates single file compressed versions of your JavaScript and CSS for production use 1 To make sure the compressed files are up to date before packaging you might consider putting this in your application s Rakefile Warbler Task new task war gt asset packager build_all You can also create multiple Warbler Task configurations in your Rake file You might do this if you wanted to build two different war files from the same code base Just pass a different name for the main task in an argument to Warbler Task new For instance let s say we wanted to create an extra war file that had its Rails environment set to staging for use on a staging server Here s what we d add to our Rakefile production_task Warbler Task new staging_task Warbler Task new C war_staging staging_task config webxml rails env staging staging_task config war_name staging To build these two war files y
153. ctive Shell Just as Ruby ships with irb for trying code interactively JRuby has jirb jirb irb main 001 0 gt Hello world join gt Hello world irb main 002 0 gt ybuRJ morf reverse gt from JRuby irb main 003 0 gt As with the REPL from any other dynamic language jiro gives you instant feedback on the results of each command you type into it Although this technique is a great way to explore the language we re guessing that you re interested in running some actual programs too 1 4 The Command Line To get a feel for running interpreted and compiled programs in JRuby we re going to write a really trivial program and run it in a couple of different ways The Simple Case Put the following code into a file called example rb Download introduction example rb puts So how are you liking the pace so far pace loop do puts 1 Move it along puts 2 Just right puts 3 Not so fast 10 Read eval print loop an interactive environment for programming Report this copy is P1 0 printing Janua THE COMMAND LINE res gets to_i break res if 1 3 include res end puts pace 2 Great see you in the next section Thanks we ll see what we can do Now run it from the command line like so jruby example rb Go ahead and give us an answer we can take it So how are you liking the pace so far 1 Move it along 2 Just right 3 Not so fast
154. d such as data validations and callbacks With ActiveModel you can easily make any Ruby object not just database classes at home in Rails Bundler Although not part of Rails Bundler is a utility developed in parallel with the Rails 3 release to aid in gem dependency management in any Ruby project even a non Rails one Bundler locks down your dependencies to make sure you can repeatably deploy the same configuration across different environments and machines You ll get comfortable with Bundler in the tutorial shortly Most parts of Rails work fine on their own even in non Rails applica tions For instance ActiveRecord is widely used in other frameworks and applications That said some components are more reusable than others There s a lot functionality just in the Rails core Thanks to the plug in architecture there s also a universe of extensions available to take Rails in more directions or sometimes fewer directions the Rails team will often spin off a seldom used feature into a plug in What About JRuby on Rails The previous sections described how Rails is put together and we will soon take a look at how to actually create an application using JRuby on Rails But first why would you want to use JRuby together with Rails The short answer for exactly the same reasons you would want Report erratum P1 0 printing January 2 WHAT IS RAILS lan Says A RESTful web service provides a set of discove
155. d Historian1 java package book embed import java util Arrays import java util List import org jruby embed InvokeFai ledException import org jruby embed ScriptingContainer Now add the bare minimum connection to Ruby Download ruby_from_java historian src book embed Historian1 java public class Historianl public static void main String args ScriptingContainer container new ScriptingContainer container runScriptlet puts TODO Make history here This is the simplest way to drive Ruby from Java pass in a chunk of Ruby code as a String and let JRuby handle the rest including output The ScriptingContainer class is part of JRuby s core embedding API You can compile the script using Ant ant 7 Embed Core is part of a collection of JRuby embedding APIs known together as JRuby Embed or Red Bridge A REAL LIFE EXAMPLE SOURCE CONTROL and run it using the launcher we ve provided bin historianl TODO Make history here There s nothing mysterious going on inside this launcher We re just setting up the classpath to contain both Historian and jruby complete jar If you prefer you can do this manually java cp lib jruby complete jar build classes book embed Historianl Now that Java is at least able to run a trivial JRuby program let s put some actual behavior in there Here s the new body of the main function If you re using the same filenames as we are
156. d a Text Pane for the first tab and an Editor Pane for the second You may need to scroll down in the palette to find these controls MONKEYBARS lt 253 Figure 10 3 The GUI layout Youre almost done with the GUI Drag a Button into the lower left cor ner of the layout You should now have something that looks like Fig ure 10 3 At this point we have nearly the same layout as our previous incarna tions of Bookie The controls don t have the right labels though and we need a little plumbing to connect to Ruby Before we get to that let s take a peek behind the veil and see what Matisse has done for us Click the Source button above the layout and you ll see a file of Java code Inside the listing click the just to the left of the words Generated Code The text will expand to show you the generated Swing layout code This is what Matisse has saved you the drudgery of writing One thing you may notice in the generated code is that the variable names are pretty generic jSplitPane1 jScrollPane1 and so on Let s change those to something a little more developer friendly Click the Design button to get back to the layout view Select the list control you created a minute ago In the bottom right area of the Net Beans window you should see a Properties pane for the list Inside this pane click the Code button You should see a property called Variable MONKEYBARS lt 254 Name Double click its valu
157. d a new one All of our event handlers will call update_view when they re done with their work The next event handler is for when the user selects a different chapter Download guis monkeybars src bookie bookie_controller rb def chapters_value_changed e unless e value_is_adjusting new_index e source get_selected_index old_index e first_index e last_index find i i new_index Report this copy is P1 0 printing Jan LIMELIGHT lt 260 if new_index gt 0 amp amp old_index model text view_model text model switch_to_chapter new_index update_view end end end After making sure we re actually switching chapters and not just receiv ing one of those extra Swing notifications we follow a similar flow to what we did before We grab the text of the Edit window update the model and tell the view to update the controls We need just one more event handler When the user switches from one tab to another we need to update the Preview window Download guis monkeybars src bookie bookie_controller rb def tabs_state_changed e model text view_model text update_view end Technically we need to update only if we re switching to the Preview window Feel free to add that optimization if you want There s a lot more to Monkeybars than we have time for here But you ve at least had a chance to see how it helps you split up the responsibilities of your code in an MVC like fashion In particular the busines
158. d of Java s Comparable class does Ruby s case statement calls this operator to see which branch matches the argument It s sometimes called the relationship operator because it s more general than equal ity You have already seen the first of these operators It s used to match a regular expression against a string The second version is just its inversion it will return false if it the regu lar expression matches apir These two operators create ranges usually ranges of num bers With two dots the range includes the final element and with three dots it doesn t While we re at it its worth mentioning that Ruby does not have the or operators that some languages do Why not It doesn t fit into the everything is an object model If Ruby allowed these operators then nonsensical expressions like 4 would be possible Fortunately that doesn t mean you re stuck typing x x 1 all the time Most binary Ruby operators can be combined with an equal sign and thus become an assignment operator So something like x x 5 can be more succinctly written as x 5 This ability to combine with isn t just limited to arithmetic A very common idiom in Ruby is to use the operator to say Assign a value to this variable but only if it doesn t already have a value Report erratum 1 0 printing January 2011 A CLOSER LOOK lt 285 Assume foo doesn t exist yet foo 4
159. dd to your application The directories you will spend most of your time in from now on are the following e app Contains most of the application s functionality models controllers and views e config Holds configuration settings such as the database server location e test Go on guess You ll notice we passed an extra template http jruby org option when we generated the application This flag tells Rails to apply some extra JRuby specific configuration to the new application If you are following along and ran the command yourself you might have noticed a couple of extra lines at the bottom of the rails new com mand output Download introduction_to_rails output rails rouge txt apply http jruby org apply http jruby org templates default rb gsub Gemfile this copy is P1 0 printing GOING ROUGE lt 4 108 Nick Says The rails new command supports a number of options A cou ple of the more interesting ones are database mysql for setting up an application for use with MySQL and skip active record for avoiding using ActiveRecord or databases at all See jruby S rails help new for more information JRuby needs to use the activerecord jdoc adapter gem to connect to databases via Java s JDBC API so JRuby has made some small mod ifications to the default Rails application s Gemfile What goes in the Gemfile you say We re glad you asked Installing Dependencies with Bundler Bundler
160. definitions the ones beginning with has_many describe collections The first one is simple and says that every blog has zero or more posts The assumption here is that there also exists a Post model class and that the blog posts will be a collection of these The second has_many declaration creates a many to many association It doesn t use a typical join table you can do that too using has_and_ belongs_to_many Instead it uses another Ruby class the Post model as the intermediate object Here a blog s authors are the set of people who have ever written a post on that blog There are definitely more nuances and fine tunings of data models but these pieces represent the most common uses of ActiveRecord Validations Nearly all database driven programs require data validation at some point Sometimes you want to apply constraints that are more strin gent than a typical RDBMS s primitive type checking Or you might want to catch errors before the database ever sees them ActiveRecord provides a declarative way to get this behavior by describing validations on your model class Although you can put almost anything in a validation there are several common checks you end up doing quite often This code gives a few examples of what you can specify in your model Report erratum 0 printing Janu RUBY DATABASE FRAMEWORKS lt 143 AA Ola Says ActiveRecord allows you to validate just about any property you can thi
161. der the following Java class Download rake baseball Pitcher java public class Pitcher Rx Tosses a pitch across the plate return a description of the pitch see Catcher public String pitchO return curveball To teach Rake how to compile this code into Pitcher class you create a file task file Pitcher class gt Pitcher java do sh javac Pitcher java end Since we ve marked the class file as depending on the java file Rake will use the two files modification times to decide whether the code needs to be recompiled If you re used to using Ruby s backtick operator for launching external programs for example rake javac Pitcherjava you might wonder why Rake defines its own alternative sh The answer is that sh does more than just running programs It checks exit codes so that the entire build will halt if javac detects a syntax error in the java file It also understands Rake s dry run option which prints out what each task would do if invoked for real Directories When you re using Rake with external tools such as compilers and doc umentation generators you naturally end up juggling files and direc tories a lot Rake can help you out here by automatically creating any directory structure you need For example consider the following Ruby code that generates Java documentation Report erratum Download rake baseball rakelib doc rake sh javadoc d doc java
162. ds like the official mathematical definition Download java_from_ruby ackerizer rb class Ackermann def self ack m n return n 1 if m 0 return ack m 1 1 if n 0 return ack m 1 ack m n 1 end end This implementation is far too slow for a production app as will become painfully clear after we wrap a Swing user interface around it To build our GUI we re going to use a Ruby helper called Rubeus Go ahead and install that now jruby S gem install rubeus We ll talk more about Rubeus in Chapter 10 Building GUIs with Swing on page 240 For this short example the code is simple enough to show without much explanation It s just a couple of text inputs and a button Download java_from_ruby ackerizer rb require rubygems require java require rubeus include Rubeus Swing JFrame new Ackerizer do frame frame layout java awt FlowLayout new m JTextField new 3 n JTextField new 9 JButton new gt do result text Ackermann ack m text to_i n text to_i to_s end 8 http en wikipedia org wiki Ackermann_function 9 http code google com p rubeus SEEING JAVA THROUGH RUBY GLASSES result JTextField new 10 frame pack frame show end Throw those two code snippets into a file called ackerizerro and then launch the app You ll most likely need to increase the JVM s stack size using Java s standard Xss setting together with JRuby s J pass throu
163. e jListl and change it to chapters If you then go back and view the generated source you ll see that the variable name has now changed Using the same method change the variable names for the following GUI components e jTabbedPane l click the gray area just above the tabs Change to tabs e jTextAreal click the first tab and then the white area underneath Change to edit e jEditPanel click the second tab and then the white area under neath Change to preview e jButtonl Change to add_chapter While we re at it lets change the tab names Click the first tab wait for a second and click it again Change the name to Edit Do the same for the second tab which you ll call Preview and for the button which you ll call Add Chapter You re in the home stretch now just a few more properties to set In the previous sections we had to pass certain parameters into our controls when we created them For example we had to pass a Default ListController into the JList constructor We ll need to wire up the same kinds of code related properties in Matisse Select the chapter list inside the layout and then in the Properties win dow click the Properties button In the row containing the model prop erty click the button to the right of the value A dialog will appear choose Custom code and enter the following new javax swing DefaultListModel Once you ve closed the dialog box look right below the model property
164. e careful not to remove them unless you know what you re doing Report erratum P1 0 printing January 2 PACKAGING FOR DEPLOYMENT lt 196 Warbler Extras Warbler is built upon Rake internally and draws heavily on lots of Rake features Even the command line is structured the same as Rake So in order to receive a list of available tasks that Warbler can do for you you use the T or tasks option Download rake sessions warble_t txt jruby S warble T warble config warble executable warble gemjar warble pluginize warble version warble war warble war clean warble war debug Generate a configuration file to customize your war Feature make an executable archive Feature package gem repository inside a jar Install Warbler tasks in your Rails application Display version of Warbler Create the project war file Remove the war file Dump diagnostic information As you can see from the previous list there are several additional tasks that you can use to extend your war or integrate Warbler better with your application s build process Running warbler pluginize installs a small warbler rake designed to be used in a Rails project directory Download rake sessions warble_pluginize txt jruby S warble pluginize mkdir p vendor plugins warbler tasks Looking at warbler rake we see the following Download rake sessions warbler rake require warbler Warbler Task new You could of
165. e performance advantages to this approach but it does tend to make for more low level code to handle everything 8 http en wikipedia org wiki Here_document RUBY DATABASE FRAMEWORKS lt 149 When performance and memory usage are not an issue you can gloss over results sets and just use the select_all and select_one methods shown earlier So let s see how this works Download databases dbi_result rb require rubygems require dbi DBI connect DBI Jdbc mysq1 localhost using_jruby Poot driver gt com mysql jdbc Driver do dbh sth dbh prepare SELECT FROM blogs sth execute while row sth fetch puts Values from DB row inspect end sth finish end Not much difference really You call fetch on the statement object and it will return a new row every time until there are no more rows to return Its important to call finish after you re finished with the state ments otherwise the database will stop responding at some point Not fun The statement object actually has a Ruby style each method so you can iterate over it like a traditional Ruby collection instead if that strikes your fancy DBI also supports preparing statements with placeholders for data This works like in JDBC the data will be quoted correctly based on what kind of column it s going into This is very convenient and also makes it much easier to avoid security holes ActiveRecord has taken a lot of fla
166. e the amount of boilerplate you need like looping and splitting Combined with flags like 0 and F you can create some pretty powerful one liners enter something at the console and assigns the resulting input to the _ global variable The a flag adds autosplitting to this loop it calls Ruby s String split on the input and stores the resulting array in the global variable F The p option prints out the value of _ at the end of each pass through the loop Here s what these flags look like in action jruby n e if _ quit exit else puts you said _ end hello you said hello goodbye you said goodbye quit t tbo t jruby a n e if _ quit exit else puts F end hello goodbye hello goodbye quit t 4 ft 4 jruby p n e if _ quit exit else _ last line _ end hello last line hello goodbye last line goodbye quit tetet An experiment paints a thousand words We highly encourage you to try these flags together or separately on a short test program this copy is P1 0 printing Janua COMMAND LINE OPTIONS lt d 305 F pattern The F flag and the global are a matched set They specify what char acter to use by default for splitting strings into arrays jruby F bar e p foobarbaz split foo baz Normally JRuby will split strings on spaces if you call split without any parameters but we ve over
167. e their own cus tom scripting interfaces Others run on web servers and can be driven through HTTP And if all else fails you can grit your teeth and code to a full on GUI automation framework Report erratum ACCEPTANCE TESTING lt 221 9 2 Acceptance Testing If you re testing a program through its user interface youll need some kind of automation library tailored to the GUI technology you re using There are libraries out there for Swing SWT Flash HTML and more Once you ve seen how to hook one or two of these up to Cucumber you should be able to do so for any of them So we re going to go for bang for the buck here and just look at web testing frameworks After all there s a fair chance you re coming to this book from the web development world Your approach to writing your scripts should suit the type of web appli cation you re testing Some apps are really simple they wait for a net work request and then reply to it with HTML You don t need a real web browser to drive these just a Ruby script that knows how to send a request and what kind of reply to expect Other web applications may involve multiple requests authentication cookies JavaScript and so on Rather than teaching Ruby to understand all of these concepts you may find it simpler to launch a regular web browser and use its scripting interface to visit the site In this section we re going to write a few different styles of test We ll
168. e to avoid name clashes by putting compiled code into packages JRuby has you covered here Since most of the other compiler hints have names that start with java_ perhaps you ve guessed that the way to specify a Java package name is to use the java_package directive Download compiler waveform waveform_with_package rb java_package com example If you add the previous line to your Ruby file the resulting Java class will be generated into the com example package Implementing an Interface Most Java based systems will eventually need to implement an inter face For jrubyc you can do this by specifying java_implements inside the body of the class Download compiler waveform waveform_with_interface rb require java java_package com example class Waveform java_implements Runnable other methods here java_signature void runQ def run puts inside runnable implementation puts rms end end this copy is P1 0 THE DETAILS Remember since jrubyc generates Java source you must implement all of the interface s required methods Otherwise you ll get a compiler error from javac Adding Annotations to a Class or Method Many Java frameworks require you to add annotations to your classes or methods These annotations may be used to tag tests indicate de pendency injection points or configure a database mapping In jrubyc you can specify annotations using the java_annotation line He
169. e_model rb class BookieModel attr_reader chapters attr_accessor text index def initialize chapters text index 0 end def add_chapter chapters lt lt switch_to_chapter chapters size 1 end def switch_to_chapter new_index chapters index text text chapters new_index index new_index end end This code is similar to what you ve written in the previous exercises But notice one key difference there is no reference of any kind to the GUI or to Monkeybars This is just a simple class that holds a list of chapters plus an index and text denoting the currently selected chapter All the knowledge of the GUI is in the view and the controller View Let s turn to the view All the modifications you ll make to src bookie bookie_view ro will go inside the BookieView class you edited a moment ago Go ahead and add the first connection to the GUI Download guis monkeybars src bookie bookie_view rb map view gt edit text model gt text Report this copy is P1 0 printing Jar MONKEYBARS lt 257 This code tells Monkeybars how to set the contents of the Edit window from the model Whenever it s time to update the view in response to some action from the user Monkeybars will run the equivalent of this edit text model text The Preview window takes its content from the model s text property as well But we need to process it to HTML before sending it to
170. ecall that the syntax editable false is shorthand for setting a Java property as in setEditable false this copy is P1 0 printing to the JList class But it s safer to confine our changes to just this one instance That s what the class lt lt chapters line does Inside add_chapter we find out how many chapters are currently on the list and then add a new item at the end We then make the new chapter the selected item Now let s move on to GUI events Download guis swing bookie rb contents Hash new chapters add_list_selection_listener do e unless e value_is_adjusting new_index e source get_selected_index old_index e first_index e last_index find i i new_index contents old_index edit text edit text contents new_index preview text RedCloth new edit text to_html end end This code creates a table to hold our chapters indexed by number and then gives the JList an event listener to update the text in the window when the user selects a new chapter The event listener is a bit of a mouthful but it s easy to understand if we break it down a piece at a time chapters add_list_selection_listener do e sex end Each time the end user selects a chapter Swing will call all the listen ers registered to that control In Java you d put your event code in a ListSelectionListener But since this interface has only one method you can just pass a Ruby block to add_list_selection_
171. ecord instead it allows you to work with a thin wrapper over the direct database driver Report erratum 0 printing Janu RUBY DATABASE FRAMEWORKS lt 147 It was originally heavily inspired by the Perl DBI library but has now diverged a bit with the addition of more idiomatic Ruby features DBI works well with JDBC and once you are connected to the database using JDBC you can use the standard DBI interface to work with your data The JDBC interface for working with DBI is still quite young so make sure to play around with it before committing to it To use DBI you first need to install the dbi and dbd jdbc gems jruby S gem install dbi dbd jdbc Once you have these in place you can connect to a database and grab some data The multirow select_all method is the workhorse of DBI Download databases dbi_test rb require rubygems require dbi DBI connect DBI Jdbc mysq1 localhost using_jruby root driver gt com mysql jdbc Driver do dbh p dbh select_all SELECT FROM foo end For single row queries you use the select_one method instead Here s how to get the current version of a MySQL server Download databases dbi_version rb require rubygems require dbi DBI connect DBI Jdbc mysql localhost using_jruby root driver gt com mysql jdbc Driver do dbh row dbh select_one SELECT VERSION puts Server version row 0 end If you want to run a script that u
172. ed language This means that all objects must be of exactly one class Unlike Java you can create classes and add or remove methods at any time even while your program is running A CLOSER LOOK lt 4 276 Ruby is also a single inheritance language although that is not the full story In Ruby just like in Java every class has exactly one parent class or superclass If you don t specify one it will be Object So everything is an object and all objects must have a class Does that mean classes have a class too Yes and as you might have guessed it s called Class And like all classes Class has a superclass it s called Module and we ll encounter it in a little while Have we tied you in a knot with all this abstract talk Let s breathe some life into these lofty concepts with some real code Imagine you want to keep track of all the various ways to reach your authors by phone mail and so on In this admittedly contrived example you might define a class called Locator that could represent a phone number or street address class Locator def initialize location location location end end Any Ruby method named initialize acts like a Java constructor Ruby calls this method automatically for each new object Unlike Java con structors Ruby initializers are inherited When we get around to defin ing PhoneNumber and Address classes we won t need to write initializ ers for them they ll use Locators v
173. edded Ruby compile modes 74 hashing Ruby filenames 95 implementing Java interfaces 92 importing Java classes 91 Java package names 92 94 just in time JIT compilation 80 81 83 302 306 properties 306 jruby_head 22 JSR 223 framework 71 72 JtestR background server 229 integration with Ant 229 integration with Maven 231 reusing Java tests 231 JUnit 233 239 JVM Java Virtual Machine JRuby options 299 302 L layout managers 246 248 libraries external C 309 314 setting classpath 38 40 wrapping Java libraries 34 35 wrapping Ruby libraries 62 63 Limelight 260 268 SLOAD_PATH 40 Mo macros 209 211 Make 165 166 managed beans 317 318 Matisse GUI Editor 251 255 Maven executions 181 integration with JtestR 231 integration with Rake 181 integration with RSpec 182 JRuby Rake plug in 180 183 methods adding annotations 93 calling Java methods 34 35 class 278 279 implementing Java interfaces 54 55 instance 44 Java target method selection 290 291 mocking and stubbing 212 217 optional arguments 279 280 overloaded Java methods 50 53 parameter passing 45 50 64 68 redefining 279 rest arguments 279 MICROSOFT SQL SERVER RSPEC static 43 Microsoft SQL Server 136 migrations 111 113 138 141 Mocha 216 217 mocking and stubbing Mocha 216 217 RSpec Mocks 213 216 Model View Controller MVC design pattern 100 243 models in Monkeybars 250 256 in Rails 106 111 11
174. edding Ruby into Java and now using the compiler Where do we go from here Out into the world There s a rich set of Java and Ruby libraries out there ready for you to tame and bring into your own applications In the second part of the book we ll visit some of the more interesting libraries in both languages Our goal isn t to cover all the popular libraries but to highlight the ones that people new to JRuby usually ask about first We ll start off by get ting Rails the blockbuster web development framework up and run ning on JRuby We ll then look at popular libraries in both languages for building and testing software Finally we ll top things off with various approaches to designing Ruby GUIs on top of the Swing toolkit Report erratum 0 printing January 2011 Part II JRuby and the World 5 1 Chapter 5 Introduction to Ral Rails is the most cited reason that people are turning to Ruby from other languages It has with good reason been called Ruby s killer application From the initial release in July 2004 up to now the in crease of Rails adoptions products books blogs and articles has been staggering In this chapter we will first take a quick look at the different parts of Rails and where all the buzzwords and slogans fit into the picture Next we ll create a simple JRuby on Rails application from scratch the focus will be on getting up and running quickly rather than providing encyclopedi
175. ee eee ee ee 217 9 Beyond Unit Tests 218 9 1 Writing High Level Tests with Cucumber 218 9 2 Acceptance Testing s s lt o ce ee Hee es 221 9 3 Plugging nto Java 664546544 e466 ee 4 24 229 94 Wrapping Upe e s s sema ae beet ee Bee a a hs 239 10 Building GUIs with Swing 240 10 1 JRuby to the Rescue osasse sasae is 240 10 2 SWING ea ay pad eea WE aer T CHER EEE ES 241 10S RUDUS oeeo dien EG ee EG he EH ee ee eS 246 10 4 Monkeybars lt 6 eS on ee A a eA 250 10 5 Limelight lt s 252465258 6 564 eho Rewe es 260 10 6 Wrapping Up ioe 44 G2 6 es bh Be Rea kA 268 III Reference 271 A Ruby 101 272 Aol M etRUDY c o pcb eee owed She bee sas 272 A2 AClOser LOOK scores ea da ei he ARS ea eS 275 AS Getting thedJob Done cec6 ce eee ee 289 B Ruby Java Interoperability 290 B 1 How Method Selection Works 290 B 2 Parameter Types gt ec eS ea taea ae ek we ee 291 BS Return Values cpc 204 4 bah o 4 ee e 292 C Configuring JRuby 294 C 1 Command Line Options 294 C2 PROD CTEGS ive se gee a oe ee eo de howe WU ee eee che 306 D Calling External C Code 309 D 1 Foreign Function Interface 309 Report erratum is P1 0 printing January CONTENTS E JRuby for Sysadmins 315 E 1 Automating Tasks 4 315 E 2 Monitoring Applications 316 ES Wrapping Up res ewa a tei ob 42 eee ES 321 F Limelight Example Source 322 G Bibliography 330 Index 332 For
176. ence_of name has_many reviews has_many comments as gt commentable scope alphabetized order restaurants name ASC end this copy is P1 0 printing Jar OPEN TO THE PUBLIC Ww lan Says Relations are Rails 3 s way of expressing database operations like sorting or filtering They let the database do what it s good at slicing and dicing data and they let Ruby do what it s good at readable notation One nice feature of relations is that they re composable If you defined two relations called in_zip_code and alphabetized you could write Restaurant in_zip_code 97201 alphabetized For more on what relations can do take a look at AREL CA Relational Algebra the muscle behind ActiveRecord x http github com rails arel Now we need to put this list of restaurants in the view so that the reviewer can choose among them Rails s collection_select method will construct the right HTML lt select gt tag for us Add the following lines just above the restaurant title in app views reviews _form html erb Download introduction_to_rails rouge app views reviews _form html erb lt div class field gt lt f label restaurant gt lt br gt lt collection_select review restaurant_id restaurants id name gt lt div gt As you can see we ve had to pass in five somewhat opaque parame ters These become less mysterious once you have the decoder ring Together they specif
177. ene edit_pane style height 0 scene preview_pane style height 90 scene preview_tab style background_color sky_blue scene edit_tab style background_color white end def save if current_chapter current_chapter text scene edit_pane text scene preview_pane text current_chapter text end end end i Download guis limelight bookie devtool props rb refresh players gt button text gt Refresh Download guis limelight bookie devtool styles rb devtool width 100 height 100 background_color light_gray horizontal_alignment center vertical_alignment center Download guis limelight bookie devtool players refresh rb module Refresh def mouse_clicked e production theater stages map do stage scene stage current_scene production producer open_scene scene name stage if scene end end end p HE wf t is copy is P1 0 printing NUA or Shohei Ta z this copy is 0 printing Janua BLS94 CAD 09 Dij76 Fow03 HCO7 HTOO Mar06 RTHO8 Appendix G Jess Borgeson Adam Long and Daniel Singer The Com pleat Works of Wilm Shkspr Abridged Applause Theatre amp Cinema Books New York NY 1994 David Chelimsky Dave Astels Zach Dennis Aslak Helles y Bryan Helmkamp and Dan North The RSpec Book The Pragmatic Programmers LLC Raleigh NC and Dallas TX 2009 Edsger W Dijkstra The problem of The Next Permutation chapter 13 Prent
178. er Not only is there no background server but there are also fewer security restrictions on the kind of scripts you can run The user story for the web search looks exactly the same for Watir as it did for Selenium the only things that need to change are the step definitions and the setup teardown code Here are the new step defini tions Download beyond_unit_tests watir step_definitions search_steps rb Given AI am on the search home page do browser goto http www yahoo com end When AI search for C A do term browser text_field name p set term browser button id search submit click browser wait end Then Athe page title should begin with A J do title browser title 0O title length should title end and here s the new setup teardown code Download beyond_unit_tests watir support env rb require firewatir browser Watir Browser new at_exit browser close As you can see the API is similar to Selenium s but has a certain Ruby je ne sais quoi The trade off for this elegance is compatibility As we mentioned Watir comes in several browser specific flavors As of this writing only FireWatir the Firefox version is known to work well with JRuby To install it run the following jruby S gem install firewatir lt 4 223 ACCEPTANCE TESTING lt 224 Ww lan Says Webrat is part of a family of related web testing libraries that have similar APIs
179. eral adapter Download databases simple_connect rb require rubygems require active_record ActiveRecord Base establish_connection adapter gt jdbc driver gt com mysql jdbc Driver turl gt jdbc mysql localhost using_jruby username gt root password gt ActiveRecord Base connection execute CREATE TABLE FOO1 Cid INTEGER p ActiveRecord Base connection execute SHOW TABLES You may need to change some of the parameters to suit your circum stances The code assumes that you ve done the following 1 Install and start the MySQL server 2 Download and extract the MySQL JDBC drivers and copy the jar to JRuby s lib directory 3 Use the MySQL server s admin tools to create a database called using_jruby mysql user root Welcome to the MySQL monitor Commands end with or g Your MySQL connection id is 4 Server version 5 1 44 Source distribution Type help or h for help Type c to clear the current input statement mysql gt CREATE DATABASE using_jruby Query OK 1 row affected 0 00 sec mysql gt q Bye 3 http dev mysql com downloads mysql 4 http dev mysql com downloads connector j this copy is P1 0 printing lt q 137 RUBY DATABASE FRAMEWORKS lt 138 Once those steps are complete you re ready to run the code jruby simple_connect rb Tables_in_using_jruby gt FO01 If you choose to use the specific M
180. eral assert method will mark a test as failed if the value passed in is nontrue in other words is false or nil The assert_equal method will compare its arguments using the Ruby operator Lastly assert_raises will make sure that a block of code raises a specific error RSpec RSpec is the tool that managed to bring Behavior Driven Development to the masses It continues to challenge us to change the way we think about writing software to get to the heart of what Test Driven Devel opment was originally about Every test framework has at its core methods to check the truth or falsehood of statements about the code Test Unit has the assert_ family of methods By contrast RSpec has expectations which are methods added to every Ruby object at test time These methods are should and should_not Expectations take one argument an expression describing the behavior of some piece of the program Here are a few examples false should be_true redivider reverse should redivider 1 2 3 should include 1 should be_empty 1 should_not be_empty hello should match ell1 proc Math sqrt a string should raise_error ArgumentError 1 Ifwe had cleanup tasks to run after each test we could put them in a similar teardown method 2 Test Unit also provides an assert_nothing_raised check but it s usually not necessary Test Unit already interprets exceptions thrown by your code as failures Report erra
181. erally takes some intermediate inter preted form like JRuby s AST and converts it to a faster more direct representation The textbook definition of a compiler is somewhat more specific than we have time or space for here For now it s fine to think of a compiler as a tool for converting code from one form into another form Compiling a Ruby program is conceptually similar to compiling a Java program 1 http en wikipedia org wiki Abstract_syntax_tree Report erratum COMPILER 101 The process involves several stages of compilation 1 From rb source to JVM bytecode the resulting bytecode may live in memory or in a class file 2 From JVM bytecode to a VM specific internal representation 3 From the internal representation to native machine code 4 and conceptually several smaller phases at each level The compilers used at each stage can be roughly classified into two kinds just in time JIT and ahead of time AOT Just in Time Compilation You ve probably had more exposure to JIT compiled languages than you realize Just in time compilation is the act of taking executable code often code that s already running in an interpreter and compiling it quietly behind the scenes without any user intervention Some platforms such as Microsoft s NET runtime have no interpreter Their JIT compilers run immediately before the program is executed Other platforms including many JVM implementations perf
182. erences from Parameter Passing Kept as a Java object not converted to Ruby but gains some Java la g String Ruby methods If you need a true Ruby String call to_s java util List or Kept as a Java collection not converted to Ruby but gains some java util Collection Ruby methods If you need a true Ruby Array call to_a Kept as a Java array not converted to Ruby but supports basic Primitive attay indexing If you need a true Ruby Array call to_a Figure B 3 Return type edge cases When no simple mapping between Ruby and Java types exists JRuby uses the conversions in Figure B 2 B 3 Return Values What about returning values back to the Ruby world Most of the conversions we ve discussed in this appendix work the same in the other direction from Java to Ruby The exceptions are discussed in Figure B 3 port erratum this copy is P1 0 printing Janua d exclusively for Shohei Tanaka RETURN VALUES lt 293 There s no need to carry these tables around on little laminated cards or anything The conversions we ve seen are designed to stay out of your way and call the right overload with a minimum of typing on your part For that 1 percent of the time when you need to specify an overload you can use java_send java_alias and java_method C 1 Appendix C nfsuring JR This chapter is a reference to the most common command line argu ments and runtime properties for
183. erratum 1 0 printing January 2011 LIMELIGHT lt 262 Production Normally you d create a new Limelight app by creating a production and populating it with a scene jruby S limelight create production bookie cd bookie jruby S limelight create scene bookie But like the cooking show parody in the abridged version of Titus An dronicus we re going to haul a fully baked pie out from under the counter instead Why are we taking a shortcut Because Limelight programs tend to be quite a bit longer than their counterparts in other frameworks That s the downside of all that customizability You can still see the full source code by thumbing ahead to Appendix F on page 322 or by downloading it from the book s web page Once you have a bookie directory containing the entire project you can launch the app from inside that directory by using the open command jruby S limelight open A screenshot of the finished app appears in Figure 10 4 on the follow ing page The colors and styles are reminiscent of a more conventional Swing app but this version definitely has its own distinctive look To see how we arrived at that look let s go through some of the more prominent files in the project structure First peek inside production rb In a new Limelight project this would contain lots of commented out examples of how to attach Ruby code to various phases of the applica tion s life cycle We ve edited i
184. ersion 1 5 5 with spe cific versions of various libraries we mention in the text If you want to use a newer version of JRuby or one of the libraries see http github com jruby using_jruby to track our updates to the example code If something isn t working or you have a question about JRuby that we haven t covered here please let us know in the forums at http forums pragprog com forums 125 We d love to hear from you Report erratum 0 printing January 2011 OLONNAVA DINER CONES Conventions Let s skip the description of which fonts we re using for code and em phasis shall we You ll pick that up from context But there are a cou ple of situations that your typical tech book doesn t have to face It s probably worth adopting a few new conventions for those The first is function names Books seem to have a tradition of spelling functions and methods with trailing parentheses as in a Java class s main method In Ruby though parentheses tend to be optional and there are some contexts where they re almost never used So we ll fol low that dual convention in the print and PDF versions of this book When we mention function names in the text you ll see parentheses after someJavaMethod but not after some_ruby_method The next convention we ve adopted is a single notation for the command line for the most part Windows command prompts use something like C gt as your cue to begin typing wh
185. ersion automatically unless we tell them otherwise There is only one line of code in this method but it s an important one It creates a new instance variable called location and assigns the value of the incoming location argument to it As with the other variables we ve seen so far in this appendix you don t need to declare Ruby instance variables They just spring into being the first time you assign something to them as we re doing here We are making sure that every Locator that gets created will have an instance variable called location By itself Locator isn t terribly useful Let s define a couple of kinds of locators class PhoneNumber lt Locator def valid location A d 3 d 3 d 4 end end Report erratum P1 0 printing January 2011 A CLOSER LOOK lt 277 class Address lt Locator def valid location A d end end Both PhoneNumber and Address are defined to be subclasses of Locator which we indicate with the left angle bracket after the class name The next line of each class defines a method called valid The trailing ques tion mark is a Ruby convention that says this method is intended to be used as a boolean The body of each valid method checks whether the contents of the location variable match a particular pattern The pattern given in a regular expression syntax similar to java util regex Pattern does some extremely basic verification Phone numbers will matc
186. eshooting jdb debugger 299 JRuby debugging options 298 299 308 profiling 300 301 truthiness 283 type conversions 46 50 76 291 292f U unit testing Mocha 216 217 mocking and stubbing 212 217 RSpec 202 205 RSpec Mocks 213 216 Shoulda 207 211 test spec 205 207 Test Unit framework 200 202 ZenTest tools 212 unit_diff 212 UNIX signal callbacks 312 314 Vooo views 123 126 250 256 259 Vim 26 Wo war files 188 192 Warbler application autodetection 191 192 application deployment 189 configuration 193 195 gem packaging 192 194 installing 188 task listing 196 war file structure 188 191f web xml creation 192 195 Winstone web server 197 Watir 221 223 224 web testing frameworks Selenium 221 223 Watir 223 224 Webrat 224 228 Webrat 224 228 Win32API 310 Windows library calls 311 312 Winstone 197 es ZentTest 212 Available in paperback and DRM free eBooks our titles are here to help you stay on top of your game The following are in print as of January 2011 be sure to check our website at pragprog com for newer titles Title Year ISBN Pages Advanced Rails Recipes 84 New Ways to Build 2008 9780978739225 464 Stunning Rails Apps Agile Coaching 2009 9781934356432 248 Agile Retrospectives Making Good Teams Great 2006 9780977616640 200 Agile Web Development with Rails 2009 9781934356166 792 Arduino A Quick Start Guide 2011 9781934356661 275 Beginning Mac Programming
187. ess to do anything out of the ordinary Since we ve shown how easy it is to manipulate files execute commands and invoke arbitrary chains of tasks with Rake why not extend your Maven project with it The jruby rake plugin for Maven allows you to do just that Add the Plug in to Your POM Here we need to assume you know a bit about how Maven pom xml files are structured and are sufficiently vaccinated for angle bracket syn drome We ll be adding some plug in configuration and wiring up Rake tasks to specific phases of the Maven build If you need some back ground you can visit the main Maven website http maven apache org pom htmil for details To start ensure your pom xml has a project build plugins section and add the jruby rake plugin as shown You can freeze to a specific JRuby release by specifying a value in the lt version gt tag as we ve done here or just omit it to pick up the latest release Download rake maven pom outline xml lt project gt lt build gt lt plugins gt lt plugin gt lt groupId gt org jruby plugins lt groupId gt lt artifactId gt jruby rake plugin lt artifactId gt lt version gt 1 5 5 lt version gt lt plugin gt lt plugins gt lt build gt lt project gt Report erratum Add an Execution Each Maven plug in declaration allows for one or more executions Each execution is bound to a build phase This means we can bind and trig ger the rake plug in to more than o
188. esulting class file would be named something like 804618fe4c994ba2b7a39b949cae81C9301327 class Deploying to Mobile Platforms When you compile a Ruby class to bytecode JRuby normally saves one last stage of code generation for runtime This stage builds method handles one tiny Java class per Ruby method basically Some plat forms place restrictions on this kind of last minute generation For example the Android mobile operating system forbids any runtime code generation Report erratum is P1 0 printing January 2011 WRAPPING UP For these cases you can pass the handles option to jrubyc You ll typi cally use this alongside the previously discussed shal flag jrubyc shal handles When you use this option you ll see lots of extra little class files There s nothing to be alarmed about these are just the method handles that JRuby would normally have generated at runtime 4 4 Wrapping Up We started this chapter with a heady discussion of compiler nerd the ory But it was for a good cause That background information was useful to keep in mind as we considered all the different ways that JRuby can compile your Ruby code Most of the time your Ruby code can coast through JRuby s just in time compiler If you need more con trol for a particular project jrubyc and its many options are there for you By this point you ve been through all the core pieces of JRuby call ing Java from Ruby emb
189. et s look at another version of our HashMap test Download testing_with_jruby shoulda hashmap_shoulda rb require rubygems require shoulda require java java_import java util HashMap class HashMapTestCase lt Test Unit TestCase context New hashmap do setup do map HashMap new end 4 In Shoulda macros are reusable customizable tests The name evokes the more pow erful Lisp macros that inspired them RUBY TEST FRAMEWORKS lt 208 AA Ola Says ThoughtWorks has written several of the largest Rails applica tions in the world and for a number of these the developers chose Shoulda over RSpec Why They felt that extending the framework with custom tests and assertions was much more complicated in RSpec Since that time RSpec has improved its support for writing matchers but Shoulda is still held in high regard should be empty do assert map isEmpty end should raise error on entryset iterator next do assert_raises NativeException do map entrySet iterator next end end context with one entry do setup do map put hello world end should not be empty do assert map isEmpty end should have size one do assert_equal 1 map size end should associate a value with a key do assert_equal world map get hello end end end end this copy is P1 0 printing Jc RUBY TEST FRAMEWORKS lt 209 To run the example install the gem jruby S gem instal
190. ew project directory and copy a freshly downloaded or built version of jruby complete jar into it remove any version numbers from the filename Now put the following code in scrape rb Download rake scrape scrape rb require rubygems require open uri require hpricot doc open http pragprog com categories upcoming do page Hpricot page end doc div book each do book title book at div details h4 inner_htm href book at div thumbnail a href puts f title is at fhref end We re not going to spend a lot of time dissecting the code here A quick glance should give you the basic idea we fetch a specific URL and then search through it for the HTML tags we re interested in Before we move on to packaging make sure the program works jruby scrape rb Cocoa Programming is at http pragprog com titles dscpq cocoa programming ExpressionEngine 2 is at http pragprog com titles riexen expressionengine 2 4 http github com whymirror hpricot PACKAGING FOR DEPLOYMENT lt 185 Hello Android is at http pragprog com titles eband3 hello android iPad Programming is at http pragprog com titles sfipad ipad programming SQL Antipatterns is at http pragprog com titles bksqla sql antipatterns The RSpec Book is at http pragprog com titles achbd the rspec book During development the line require hpricot loads a library from your system s RubyGems path Your end user s system is
191. eword by Matz I love the term diversity Di ver si ty Doesn t that sound great JRuby surely embodies the value of diversity Some might think we can utilize our resources more efficiently without diversity But in the open source world the number of resources that is contributors is not really limited If a project is really attractive we can get more people interested in it If we had a less diverse ecosystem without projects like JRuby I don t think we would get more resources Instead a lot of existing contributors would have dismissed Ruby for lack of diversity I created Ruby to make my programming happier Since its creation it has helped other programmers as well Iam proud that my masterpiece has made the world of programming a little bit better JRuby made the Ruby language reach the Java world JRuby made it possible to run Ruby on platforms like Google App Engine and Android For this one thing I will appreciate JRuby forever Long live JRuby Long live diversity in the Ruby world I hope you will enjoy Ruby on the JVM Ruby will be with you Enjoy programming on whatever platform you love Yukihiro Matz Matsumoto August 2010 Foreword by Bruce T In late 2004 I was a Java author riding on an airport bus with Dave Thomas At the time I was frustrated with the increasing complexity of the Java language but thinking it was the only game in town Dave con vinced me to give Ruby a try When I finally did I
192. f chapters along with the event listener that manip ulates it is nearly the same as in pure Swing Again we are using in stance variables instead of local variables The following code goes right after the previous excerpt still inside the split pane Download guis rubeus bookie rb contents Hash new chapters add_list_selection_listener do e unless e value_is_adjusting new_index e source get_selected_index old_index e first_index e last_index find i i new_index contents old_index edit text edit text contents new_index preview text RedCloth new edit text to_htm end end Now for a few containers to carry all this stuff Because the JlabbedPane lives inside a JScrollPane their constructors follow the same nesting This is the last piece of code inside the split pane Download guis rubeus bookie rb JScrol1 Pane new preferred_size gt 400 250 do scrol1 JTabbedPane new TOP SCROLL_TAB_LAYOUT do tab tab add_change_listener do event if tab selected_component preview preview text RedCloth new edit text to_html end end edit JTextPane new preview JEditorPane new false HTMLEditorKit new preview editor_kit create_default_document preview editable preview editor_kit preview document tab set_titles Edit Preview end end Another shorthand that Rubeus allows is passing in common options to a component s constructor In the previous e
193. f course live on as long as the Java side holds a reference If you ve tried the techniques we ve described here and are still stuck you may want to peek at the relevant section of the JRuby wiki 13 2 9 Wrapping Up We ve been all over the map this chapter from the basics of loading libraries to the minutiae of parameter passing We ve seen how JRuby 12 Monkeypatching from a malapropism of guerrilla patching means modifying a class at runtime 13 http wikijruby org CallingJavaFromJRuby Report erratum WRAPPING UP sands off some of the rough spots where the two languages meet and how to steer around the remaining ones And we ve discussed what to do when things go wrong This broad set of topics might seem scattershot at first glance But we ve striven to show a common theme among them The examples we ve presented have all focused on the case where youre starting with a Ruby script that s calling into a Java library Of course there s been some back and forth with Java occasionally calling back into a Ruby object we gave it We re about to shift the emphasis in the Java direction In the next chapter we ll start with a Java project and add Ruby to it As with this chapter there will still be plenty of places where the two worlds are calling back and forth to each other Chapter 3 Ruby trom Java Embedding JR We ve just seen several ways for Ruby to call into Java libraries Now let s con
194. f submit Comment gt lt p gt lt end gt See the comment instance variable at the top That s the value we created with the Comment new line in the controller so that we could fill in the fields with their correct defaults This user interface is not particularly fancy But with some small touches of CSS it could be perfectly servicable Of course not every thing is hooked up yet If we want to be able to save a new comment we ll need to add an action to the GuideController Download introduction_to_rails rouge app controllers guide_controller rb def comment_on_restaurant restaurant Restaurant find params id restaurant comments create params comment comment Comment new flash notice Comment created render action gt show end OPEN TO THE PUBLIC We re almost finished with the app now The only major feature missing is reviews Reviewers and Reviews We ll start with a scaffold as before jruby script rails g scaffold Review title string content text migrate false skip The first change we need to make is to confine each reviewer to editing only their own reviews We ll use HTTP Basic Authentication as we did for the admin interface but with a twist we need to remember which reviewer is logged in Open app controllers reviews_controller ro and add this at the top after the class declaration Download introduction_to_rails rouge app controllers reviews_controller rb
195. f test steps and then assembles the results for JUnit 5 http jtestr codehaus org Report erratum PLUGGING INTO JAVA lt 233 Driving any of these frameworks from Ruby is as easy as any other Java integration You just call into the Java classes and methods using the same techniques we ve been discussing throughout this book That s all JtestR does when it runs JUnit and TestNG tests A JUnit Example To make this section a bit more concrete we ll take a quick look at how you can run Test Unit tests from JUnit Most of the code will be in Ruby the Java side will consist of a small JUnit adapter This general pattern a Ruby project with a thin Java wrapper pops up frequently in JRuby projects The first thing we need is a class that will present itself to JUnit as a test case We ll be using the older nonannotation JUnit API here this will work fine with either JUnit 3 or 4 The code looks like this Download beyond_unit_tests junit_integration TestUnitSuite java import org jruby embed ScriptingContainer import junit framework Test import junit framework TestCase import junit framework TestResult public class TestUnitSuite implements Test private void runTestCasesIn ScriptingContainer runtime TestResult result Object junit_adapter runtime runScriptlet JUnitAdapter Object instance runtime callMethod junit_adapter new result runtime callMethod instance run_tests public
196. for a lot of code structure questions but still requires a healthy amount of Swing knowledge Like Rails it emphasizes strict boundaries between the model view and controller which makes it especially appealing for large UI applications Its easy integration with RAD tools like NetBeans Matisse is another compelling point Limelight is the least Swing like of the frameworks The easy organiza tion and offbeat metaphors are reminiscent of Shoes the beloved GUI toolkit from the C Ruby world This independence is a double edged 10 http github com shoes shoes Report erratum is P1 0 printing January 2011 WRAPPING Up lt 270 sword On the plus side you might not need to crack open a single Swing reference manual while you re writing your app On the minus side you re going to have a hard time integrating existing Swing com ponents like the Flying Saucer HTML renderer or the WorldWind map viewer We hope you ve enjoyed touring the JRuby universe with us We ve been through a lot together from tentative first steps with the language through the best of Ruby and Java Please visit the forums to let us know how your journey went and what you re building with JRuby Happy coding 11 http forums pragprog com forums 125 Part III Reference A 1 Appendix A Remember that JRuby at its heart is just Ruby so you ll get the most out of JRuby by having a little knowledge of the language That s o
197. found a language that was more expressive and productive than anything I d ever used before In a short year I completed my first and second commercial Ruby appli cations and knew beyond a shadow of a doubt that Ruby was a better language for the types of applications I was writing I wanted to share that idea with managers like the ones I encountered in my consulting practice so I wrote From Java to Ruby TatO6 to emphasize that Ruby wasn t just a smart move for programmers Ruby made business sense Thankfully I didn t have to lean solely on my own thin experience To make the most critical points I interviewed some important experts in complex areas such as design adoption and deployment Among these people were Thomas Enebo and Charles Nutter two of the earliest committers of the JRuby project In those interviews they elegantly made the case that a mature Ruby implementation on the JVM would lead to a powerful set of advantages You see Ruby the beautiful language is only part of the story Even this powerful productive language needs a story that goes beyond the ideas embedded in the syntax and semantics Real applications will have requirements encompassing performance politics and deploy ment Truth be told in 2006 Ruby was sometimes difficult to sell into the back office for some of these reasons What a difference four years makes Thomas Charles and I have leaned hard on Ruby for these four years supported b
198. ful filtering capabilities You won t even have to resort to SQL to do subselects This capability can be very powerful but it also makes the library really easy to use You can run DELETE and INSERT statements in pure Ruby as well Download databases sequel_delinsert rb require rubygems require sequel url jdbc mysq1 localhost 3306 using_jruby user root amp password DB Sequel connect url blogs DB blogs blogs insert name gt Databases author gt Pramod Sadalage blogs filter name gt Databases delete This code does an INSERT using the parameters specified filters the table and then deletes the blogs selected by the filter This just scratches the surface on what is possible with filters in Sequel Sequel also offers models like ActiveRecord does Download databases sequel_simple_model rb require rubygems require sequel url jdbc mysq1 localhost 3306 using_jruby user root amp password DB Sequel connect url class Blog lt Sequel Model end blog Blog 1 p blog Here we first define a class that will become a Sequel model By default it will use the same naming conventions as ActiveRecord so this code will connect to the table called blogs using the existing database con nection The square brackets allow us to get a specific blog instance based on the primary key Sequel is fine with composite primary keys but also scales down in simplicity it will
199. ge war to the Tomcat webapps directory Usually webapps will be found in the Tom cat base directory If you chose to install Tomcat using your operating system s package manager it may be elsewhere for example Gentoo Linux places it at var lib tomcat 6 webapps For Glassfish use the asadmin command asadmin deploy rouge war Application deployed successfully with name rouge Command deploy executed successfully In both cases once you ve deployed rouge war you ll be able to access it in a browser at hittp localhost 8080 rouge How Warbler Packages We ve just seen a simple example of how Warbler looks for application code static assets and gem dependencies and packages them up along with JRuby and JRuby Rack into a war file rearranging the layout of the files to match the standard Java web application structure This directory shuffling is illustrated in Figure 7 1 on the next page static content gets moved to the root while application code is shuffled under the special WEB INF directory So how did Warbler figure out what to put in the war file How can you be sure that it didn t miss something Much like Rails itself Warbler is built with some assumptions about typical Ruby web applications that you d like to package and it uses that knowledge to discover what needs to be packaged If your application doesn t fit those assumptions that s fine too War bler is fully configurable We ll cover the bas
200. gems from your Gemfile Bundler configuration file 1 e Merb 1 0 applications Warbler loads the Merb environment and inspects Merb BootLoader Dependencies For all other applications you ll need to tell Warbler which gems to package See the configuration section further on for details Miscellany If you re a Java web developer you may have encountered web xml the configuration file for web applications Warbler will generate this file for you We ll get to a few of its gory details in a minute For now we ll 10 http gembundler com Report erratum PACKAGING FOR DEPLOYMENT just mention that Warbler uses this file to feed configuration settings to your app via JRuby Rack at boot time The most important of these settings is whether you re using the produc tion development or test environment Warbler provides a configuration setting in case you need something other than the default of production You might have noticed that Warbler doesn t include tests or Rakefiles by default since they are not typically needed in production This behav ior too can be overridden in Warbler s config file Previously we pointed out that Warbler packages copies of JRuby and JRuby Rack for you These jar files are sourced from the jruby jars and jruby rack gems that get installed alongside Warbler If you want to up grade these libraries you can do so by installing new versions of those gems Warbler will happily
201. gh option jruby J Xss64m ackerizer rb You should see something like Figure 2 4 on the following page Try clicking the button to calculate ack 3 9 The results will probably take several seconds to appear in the window Because our app is a one trick pony there s only one suspect worth investigating the ack method 1 There s a lot we could try in Ruby before jumping into Java At the very least we should be storing our intermediate values so that we don t have to calculate them over and over But let s say you ve done all that and you still need faster results Here s how you d move the calculation into a Java class Download java_from_ruby Ackermann java public class Ackermann public static int ack int m int n if m 0 return n 1 if n 0 return ack m 1 1 return ack m 1 ack m n 1 which you can then compile like so javac Ackermann java We need to make only one change to the Ruby code to use the new Java class In the middle of the button s on_click handler add the text Java to the beginning of the Ackermann ack call 10 On any nontrivial project you ll want to profile your code rather than relying on inspection and guesswork See Appendix C on page 294 for how to do that with JRuby DEALING WITH THE CLASSPATH 3 fo 4093 Figure 2 4 The Ackermann calculator result text Java Ackermann ack m text to_i n text to_i to_s
202. gt 2 1932s gt 0 rows AddFooTable migrated 2 19635 this copy is P1 0 printing Jc RUBY DATABASE FRAMEWORKS AddBlechColumnfable migrating s s ss s s 2 22 lt S s esse ae eee ese see add_column foo flax string gt 0 1170s gt 0 rows AddBlechColumnTables migrated 0 11905 s s lt s s s ss sssss AddBlechColumnTable reverting remove_column foo flax gt 0 0081s AddBlechColumnTable reverted 0 0092s AddFooTable reverting s s s s ss ss s sssssSsssSSSSssSSS 5 5 drop_table foo gt 0 0026s gt 0 rows AddFooTable reverted 0 00485 Migrations are definitely handy to have in your tool chest and making use of JDBC and JNDI to attach to different databases makes it much easier to do any of the DDL tasks you might want to do repeatedly Model Descriptions ActiveRecord includes a very rich DSL like syntax for describing your model classes and their associations with one other Creating a new model class is as simple as inheriting from ActiveRecord Base and then using certain class methods to tell ActiveRecord some facts about your model Instead of taking each piece in isolation we will show you a model class that uses most of the co
203. h For that we ll need a new view and controller action A Restaurant with a View Add the following method to GuideController Download introduction_to_rails rouge app controllers guide_controller rb def show restaurant Restaurant find params id comment Comment new end this copy is P1 0 printing lt q 123 OPEN TO THE PUBLIC Why are we creating a new comment here It will help us fill in some default form values in a moment Before we get to that though add a new view by creating app views guide show html erb and putting the following code in it Download introduction_to_rails rouge app views guide show himl erb lt h1 gt lt restaurant name gt lt h1 gt lt p gt lt b gt Address lt b gt lt restaurant address gt lt p gt lt p gt lt b gt Phone lt b gt lt restaurant phone gt lt p gt lt p gt lt restaurant description gt lt p gt lt h2 gt Revi ews lt h2 gt lt table gt lt tr gt lt th gt Title lt th gt lt th gt Author lt th gt lt tr gt lt restaurant reviews each do review gt lt tr gt lt td gt lt link_to review title action gt review id gt review gt lt td gt lt td gt lt review reviewer name gt lt td gt lt tr gt lt end gt lt table gt lt h2 gt Comments lt h2 gt lt restaurant comments each do comment gt lt p gt lt b gt By lt b gt lt comment said_by gt lt br gt lt
204. h if they conform to the typical U S format DDD DDD DDDD Addresses are expected to contain one or more digits a space and then one or more characters The operator also called the match operator returns a number if it finds a match and returns nil if it doesn t Because Ruby treats all numbers even zero as true and nil as false we just return the match result from the function Finally we can get to the definition of a Person class Person def initialize locators end def add_phone_number string number PhoneNumber new string locators lt lt number if number valid end def add_address string address Address new string locators lt lt address if address valid end end To be sure that we have somewhere to store all the locators for a person we use an initialize method to create an locators instance variable and set it to an empty array This class also has a couple of methods to add phone numbers and addresses Let s look at the first of those add_phone_number Inside it Report erratum A CLOSER LOOK lt 4 278 we create a new PhoneNumber object by calling new Recall that this will cause Ruby to call the new object s inherited initialize method for us with the same parameters we pass to new We store the freshly created object in a new local variable called number which like an instance variable springs into being the first time we set it to something We use the lt lt o
205. han falling back on Rake s stan dard search mechanism e args Pass arguments to Rake either task names to execute or NAME VALUE environment variables 2 http maven apache org guides introduction introduction to the lifecycle html Lifecycle_Reference Report erratum 0 printing Jar As a more extended example here s some plug in configuration to test your Java code using the expressive RSpec testing library We ll discuss RSpec in Section 8 1 RSpec on page 202 Download rake maven pom rspec xml lt plugin gt lt executions gt lt execution gt lt id gt rspec lt id gt lt phase gt test lt phase gt lt goals gt lt goal gt rake lt goal gt lt goals gt lt configuration gt lt script gt require rspec core raketask RSpec Core RakeTask new do t t pattern src spec ruby _spec rb end task default gt spec lt script gt lt configuration gt lt execution gt lt executions gt lt plugin gt Maven launches the JRuby process with the appropriate classpath so that any dependencies and Java classes compiled by Maven will be visible to JRuby and RSpec automatically Ensure Gems Are Installed Sometimes your Rake or Ruby code will need to rely on additional Ruby gems in order to function The install gems goal can be used to make sure these gems are present The jruby rake plugin will install these gems into SHOME gem jruby 1 8 Download rake maven pom gem xml lt plug
206. have saved us some effort We ll start by creating the Edit and Preview windows as a JTextPane and JEditorPane respectively Download guis swing bookie rb edit JTextPane new preview JEditorPane new preview editable false preview editor_kit HTMLEditorKit new preview document preview editor_kit create_default_document This should be fairly self explanatory We ve marked the Preview pane as noneditable because it s well a preview We also need to designate it as an HTML capable window since RedCloth renders Textile down to HTML Next we ll create a list box to contain the names of the chapters Download guis swing bookie rb chapters JList new DefaultListModel new chapters selection_mode ListSelectionModel SINGLE_SELECTION class lt lt chapters def add_chapter count model size model add_element count 1 selection_model set_selection_interval count count end end chapters add_chapter The first line creates a new JList and specifies two models one for the contents of the list and one for the selection Swing applies Model View Controller MVC concepts everywhere sometimes to an annoying degree Moreover it seldom offers sensible defaults Mastering Swing requires both writing new models and crawling through the API docs to find existing models The Add Chapter button which we haven t defined yet will need a way to append chapters to our list We could add an add_chapter method 3 R
207. hed against the familiar rocks of platform specific quirks The story is more hopeful today especially in the area of GUI devel opment If you write a Java GUI application on Windows it can also run on Mac OS Linux or any other platform where Java runs while taking on a native look and feel However for Java language developers this comeback has been hard earned Swing the primary GUI API for Java is a byzantine framework It works great once you ve invested your blood and sweat into mak ing a robust application But the amount of effort needed to learn the ins and outs of Swing often frustrates developers into abandoning the framework altogether JRuby to the Rescue There has been an explosion of GUI frameworks for JRuby Most of these work by papering over some of Swing s more puzzling complexi ties They also reduce the amount of boilerplate code you have to write by leaning on powerful Ruby features like blocks SWING lt 4 241 Why is there so much interest in JRuby GUI development As you might have guessed Java is part of the answer In Java shops enterprising coders have used Ruby frameworks to ease the pain of supporting their company s chosen platform There s another factor too mainstream Ruby The C version of Ruby has no widely used cross platform GUI toolkit Yes some builds of Ruby ship with support for the Tk graphical widget set But it s no exagger ation on our part to say that Tk is not
208. hen chances are you re using SQL either directly or through a mapping layer But most of the SQL that gets used is inefficient hard to maintain and sometimes just plain wrong This book shows you all the common mistakes and then leads you through the best fixes What s more it shows you what s behind these fixes so you ll learn a lot about relational databases along the way SQL Antipatterns Avoiding the Pitfalls of Database Programming Bill Karwin 300 pages ISBN 978 19343565 5 5 34 95 http pragprog com titles bksqla Seven Languages in Seven Weeks A Pragmatic Guide to Learning Programming Languages Bruce A Tate Batted by Jacquelyn Carter SQL Antipatte Avoiding the Pitfalls of Database Programming Bill Karwin amp n attend by cut Carter Fixing the Real Worl Your co workers resistance to new technologies can be baffling Learn to read users patterns of resistance and then dismantle their objections Every developer must master the art of evangelizing With these techniques and strategies you ll help your organization adopt your solutions without selling your soul to organizational politics Driving Technical Change Why People On Your Team Don t Act On Good Ideas and How to Convince Them They Should Terrence Ryan 200 pages ISBN 978 1934356 60 9 32 95 http pragprog com titles trevan Debug It will equip you with the tools techniques and ap
209. his case a table listing the restaurants we expect to see We need to make a similar table of the actual restaurants on the page Cucumber s Rails integration provides the tableish method for this purpose tableish takes as parameters the kinds of HTML tags we re looking for the hairy details of CSS3 selectors are a topic for another day and uses them to slice the document up into an array of Hash objects Name gt Kenny and Zuke s Phone gt Address gt Name gt Horse Brass Pub Phone gt Address gt Name gt New Old Lompoc Phone gt Address gt Did you notice the hash keys are all capitalized The ASCII art table in our scenario spelled the columns in all lowercase letters Do we rewrite the test or do some kind of translation We recommend the lat ter because it s easier to keep things up to date when the web designer changes the page The translation code is simple First we get the array of hashes into one of those powerful Cucumber table objects that s what the table method does Next we call map_headers to do the translation Finally we can compare the two tables via their diff method By default this comparison is forgiving of the extra Phone and Address columns that appear on the page but not in our test We don t care about them for this particular scenario One last thing we need to take care of the login step from the scenario backgro
210. his feature in JRuby is very expensive especially for a rarely used debugging feature If you re using a third party library that depends on this feature for advanced Ruby tech niques you ll need to set this property to true jruby launch inproc true false Ruby s system method is meant to launch an external process But if that external process would be a call to ruby or jruby JRuby will save you some time by reusing the same JVM albeit with a different JRuby instance If you really need to spin up a separate ruby process set this property to true Report erratum 1 0 printing January 2011 PROPERTIES lt 308 jruby debug fullTrace true false This property is the equivalent of the debug flag we discussed earlier It enables execution tracing for set_trace_func which many debugging libraries depend on Loading Files A related issue to code execution is code loading the final two options give you a window into that process jruby debug loadService timing true false Your app s startup performance takes a noticeable hit if you re loading complex files or doing a lot of up front code generation JRuby can help you identify the more obvious startup problems by logging how long each file takes to load together with its dependencies Set this property to true to enable load time logging jruby debug loadService true false If you have a pesky file being loaded from the wrong filesystem location and yo
211. hort description we can deduce some potential models e Restaurant e Administrator e Reviewer e Review e Comment attached to a Restaurant e Comment attached to a Review We will use a common Comment model for both restaurant comments and review comments it seems unnecessary to have two different models for essentially the same idea Establishing Structure Rails emphasizes a particular structure for your code The first step in creating a new application is to generate this structure The rails new command will build a minimal but well organized app from scratch using the directory name you provide on the command line We ll choose the name rouge for our project directory GOING ROUGE lt 4 107 Download introduction_to_rails output rails rouge txt jruby S rails new rouge template http jruby org create create README create Rakefile create config ru create gitignore create Gemfile create app create app controllers application_controller rb create app helpers application_helper rb create app views layouts application htm erb create app mailers create app models create config create config routes rb Rails tells you exactly which directories and files get created Repro ducing the entire list here would take more than two pages for the trees sake we ve truncated the output As you can see by the directory names there is one specific place for each piece of functionality you would want to a
212. html Report erratum 0 printing Jan MOCKING AND STUBBING lt 214 The basic idea is that you start with a mock object add some canned behavior to it and finally pass it into the code you re testing RSpec can create an empty object for you via the mock method but you can actually mock or stub methods on any Ruby object including classes For Java to be able to call your canned methods the mock object will need to implement a Java interface Since java util HashMap has been our guinea pig in this chapter let s see how we d use RSpec s mock objects to check one of its constructors the one that takes an existing Map What we expect is that the Java code will do the following 1 Call size on the Map 2 Ask for its entries 3 Get an Iterator from that entry set 4 Call hasNext on the Iterator until we get a false result Documenting these expectations is easy First we bring in the Java classes we need Download testing_with_jruby rspec_mock hashmap_spec rb require java java_import java util Map java_import java util HashMap java_import java util Iterator java_import java util Set Now we create a Ruby object implementing the java util Map interface and use the should_receive method to document our expectations Download testing_with_jruby rspec_mock hashmap_spec rb describe HashMap do it can be created from an empty Map do map Map new map should_receive size and_return 0 iter I
213. i posix rb module POSIX extend FFI Library FFRi_lib ie attach_function alarm uint uint attach_function sigaction int pointer pointer int remaining definitions will go here end Those two pointer parameters point to siginfo structures This structure varies from platform to platform We ll get to the Mac version of it in a minute But first we need to talk about callbacks UNIX signal callbacks can take one of two forms Download ffi defs c typedef void handler_func Cint typedef void action_func int struct siginfo void FOREIGN FUNCTION INTERFACE lt 313 Here s how to translate these two typedefs to Ruby Note that this code needs to go inside the module declaration Download ffi posix rb callback handler_func int void callback action_func int pointer pointer void Now for the data structures that house those callbacks The defini tion will look different if you re on Linux or another UNIX like system Caveat coder Download ffi defs c union sigaction_u handler_func sa_handler action_func sa_action 7 struct sigaction union sigaction_u sa_action_u sigset_t sa_mask int sa_flags K FFI provides its own Struct and Union types to represent those C entities Again these definitions live in the POSIX module Download ffi posix rb class SigActionU lt FFI Union layout sa_handler handler_func sa_action action_func end
214. ication as a standard war file and deploy it to any compliant Java web container 4 Web application archives or war files are a standard way of deploying web applica tions on Java servers Report erratum lt 104 GOING ROUGE Rails supports several different databases but in practice most shops use either MySQL or PostgreSQL Since JRuby on Rails allows you to use any database that has a JDBC driver you have access to a wider range of databases plus features such as data sources and connec tion pooling JRuby on Rails also works very well with JavaDB the in memory database that is distributed with Java The best way to think of JRuby on Rails is like regular Rails with a few intriguing new possibilities 5 2 Going Rouge It s time to get started with some code Through the rest of this chapter we ll build Rouge a simple web based restaurant guide By the time we ve finished you should be able to build your own JRuby on Rails application We can t cover all or even most of the functionality that Rails provides there are other books that can teach you this Getting Started Before starting the tutorial we need to install Bundler and Rails The example code in this chapter was written using Rails 3 0 1 Bundler 1 0 2 and activerecord jdbc adapter 1 0 1 To install Bundler and Rails just type this command Download introduction_to_rails output gem install txt jruby S gem install bundler rail
215. ice Hall 1976 Martin Fowler Patterns of Enterprise Application Architec ture Addison Wesley Longman Reading MA 2003 Cay S Horstmann and Gary Cornell Core Java Prentice Hall Englewood Cliffs NJ eighth edition 2007 Andrew Hunt and David Thomas The Pragmatic Program mer From Journeyman to Master Addison Wesley Reading MA 2000 Brian Marick Everyday Scripting with Ruby For Teams Testers and You The Pragmatic Programmers LLC Raleigh NC and Dallas TX 2006 Sam Ruby David Thomas and David Heinemeier Hansson Agile Web Development with Rails The Pragmatic Program mers LLC Raleigh NC and Dallas TX third edition 2008 TatO6 TFHO8 APPENDIX G BIBLIOGRAPHY lt 331 Bruce Tate From Java to Ruby Things Every Manager Should Know The Pragmatic Programmers LLC Raleigh NC and Dallas TX 2006 David Thomas Chad Fowler and Andrew Hunt Program ming Ruby The Pragmatic Programmers Guide The Prag matic Programmers LLC Raleigh NC and Dallas TX third edition 2008 mbols shebang 297 316 oe acceptance testing GUI automation libraries 221 web testing frameworks 22 1 228 Ackermann function 36 38 ActionMailer 103 ActionPack 102 ActiveModel 103 ActiveRecord 101 134 146 ActiveResource 102 ActiveSupport 102 Ant compile Java source files 177 create jar files 178 generate Java documentation 178 importing Rake tasks 179 integration with JRub
216. ich may have nothing to do with their filenames For example the following two lines of Ruby code refer to the same file require some_library require sub directory some_library Report erratum 0 printing January 2011 THE DETAILS e lan Says Does the SHA 1 Really Hide the Source The SHA 1 hash is generated from the Ruby source Does this mean you re once again stuck with shipping a bunch of rb files alongside your compiled code Well for now yes But the compiler will soon support stripped down rb files that contain the SHA 1 value and nothing else So you ll be protected from name collisions without having to ship your source code but the Java universe doesn t know that The next two lines of Ruby code refer to different files require math sin require mortal sin but to Java these would both be in classes called sin Clearly we need some way other than just the filename to distinguish between two different compiled Ruby files We need to know something about the file contents not just the name JRuby offers a way to name compiled files based on their source con tents The shal flag calculates a SHA 1 hash a 40 digit hex number that is overwhelmingly likely to be unique for each Ruby file in your program and uses that for the filename instead So JRuby could tell that two uses of some_ruby_class are referring to the same code because the contents would be the same The r
217. ics of custom configuration in a moment But first lets examine the basic assumptions so you know where you might need to drop into that configurability to ensure everything your application needs gets packaged 9 Web apps based on recent frameworks like Rails 3 are properly configured out of the box For older systems you may need to add some extra dependencies see Section 7 4 Warbler Configuration on page 193 Report erratum P1 0 printing January 2011 PACKAGING FOR DEPLOYMENT lt 191 v rails_app v a rails_app war jj images jj controllers jj javascripts helpers a stylesheets jj models jj views jj controllers jj helpers jj models jj views gt images jj config gt f javascripts gt i lib gt f stylesheets gt i vendor gt test gt vendor Figure 7 1 Rails vs WAR directory layouts Application Code Warbler assumes that your application code is found in any of the app config lib and vendor directories Those directories if they exist are copied wholesale into WEB INF in the war file Warbler also tries to infer what kind of application you re using so that it can set up the application boot process accordingly JRuby Rack can boot apps written to almost any Ruby web framework Rails Merb or anything else that uses the Rack API Warbler autodetects applications by inspecting the local Rake environment and looking on the filesystem 1 Firs
218. ide an object static Callable lt Object gt callable Runnable task There are two main ways to pass an interface into a Java function Implementing the Methods You can implement the Java interface completely in Ruby code Just include it in your class definition and any calls to the interface s meth ods become calls to your Ruby class Runnable has just one required method run Download java_from_ruby runnable_demo rb line require java java_import java lang Runnable class Foo 5 include Runnable def run puts foo end 10 end callable java util concurrent Executors callable Foo new callable call Report this copy is P1 0 printing Jar TROUBLESHOOTING Technically you don t have to include the interface name at line 5 JRuby can detect that this instance of Foo implements Runnable s meth ods But we like being explicit here Passing a Block For single method interfaces there s an even more direct path from Ruby to Java Instead of going through the mental overhead of creating and naming a Ruby class you can just pass a block of Ruby code straight to the Java method Download java_from_ruby runnable_demo rb callable java util concurrent Executors callable do puts foo end callable call This also works with Proc objects which are like blocks of code that can be stored in variables Download java_from_ruby runnable_demo rb myproc Proc new puts foo callable java u
219. ient families thank you for enduring our absence obsession and distrac tion To Matz thank you for creating Ruby our favorite programming language To Matz and Bruce thank you for your support of this pro ject and for the lovely forewords To the entire community of JRuby fans contributors and users thank you for your support of this our favorite implementation of Ruby Ready to jump into JRuby Let s go Report erratum P1 0 printing January 2011 Part I JRuby Core Chapter You re now standing on the threshold of the JRuby universe where you ll have your pick of the world s best Ruby and Java libraries With the techniques in this book and the tools available to you you ll be able to do amazing things with JRuby Here are just a few possibilities e Deploy a Ruby on Rails web application to Google s App Engine service e Target the latest Android smartphones with your Ruby code e Create dazzling cross platform GUIs with clean elegant code e Build your project on solid libraries written in Java Scala Clojure or other JVM languages Do these sound like intriguing projects They ll all be within your grasp by the time you reach the end of this book You ll see how to code test and package web applications for easy employment You ll learn the nuances of compiling code and how to adjust to the limitations of mobile platforms You ll design user interfaces using both graphical layout tool
220. iew with ID params id and reviewer reviewer name unless G review respond_to do format format html show html erb format xml render xml gt review end end Now consider the three other controller actions edit update and destroy All three of these act on an existing review and all three need modifications identical to the previous one The create action requires a slightly different change because it builds a new review instead of searching for and updating an existing one Download introduction_to_rails rouge app controllers reviews_controller rb def create review reviewer reviews build params review respond_to do format if review save format html redirect_to review notice gt Review was successfully created format xml render xml gt review status gt created location gt review else format html render action gt new format xml render xml gt review errors status gt unprocessable_entity end end end In the previous excerpt it wouldn t have been enough just to call Review new to create a new review We have to reach into the reviewer s reviews collection to make sure the new review gets associated with the right reviewer slusively for Shohei Ta this copy is P1 0 printing Jan vely for S A OPEN TO THE PUBLIC d 128 Matching Reviews to Restaurants As it stands there s no way for the user to specify which resta
221. ile Mac and Linux machines typically use or Windows uses backslashes to separate directory names while other platforms uses forward slashes Other than that there s little difference between invoking JRuby on one operating sys tem or the other Accordingly we re going to use the notation from bash the default shell on the Mac and on many Linux distributions When you see this jruby some_directory program rb youll know not to type the dollar sign and to use whatever kind of slashes your system requires Actually the latter is a bit of a moot point because JRuby does fine with forward slashes on Windows For the few specific cases where the syntax is significantly different between Windows s cmd exe and UNIX s bash we ll spell out both cases Speaking of differences between systems many UNIX like systems re quire you to log in as the root user before installing software Others have you preface any administration level commands with sudo Most of your authors run JRuby from regular nonadministrator directories in our own home directories making sudo unnecessary Accordingly the commands to install software in this book will typically just say gem install some_library rather than sudo gem install some_library Finally a word on program output We use three variations of the tradi tional Ruby hash rocket sign which looks like this gt to show the Report erratum 0 printing Janu ACKNOW
222. in gt lt executions gt lt execution gt lt id gt instal1 gems lt id gt lt phase gt generate resources lt phase gt lt goals gt lt goal gt instal1 gems lt goal gt lt goals gt lt configuration gt lt gems gt activerecord activerecord jdbc adapter lt gems gt lt configuration gt lt execution gt lt executions gt lt plugin gt this copy is P1 0 printing Ja PACKAGING FOR DEPLOYMENT lt 183 That s enough on building software for the moment Let s now move on to deployment 7 4 Packaging for Deployment Conceptually software deployment in regular Ruby isn t complicated The general steps go something like this 1 Install Ruby 2 Install the required libraries 3 Copy your rb files onto the target machine Depending on the kind of app though things can really break down during steps 1 and 2 The Mac you designed your GUI on may have shipped from the factory with Ruby on it but your customer s Windows box probably didn t Your web app might lean on a C based XML library that your ISP doesn t allow you to compile on their machine With JRuby a lot of these problems go away Most desktop machines already have a Java runtime on them so you might get away with out asking your users to install any extras If you re using a Ruby library that contains compiled code at least it s compiled Java code you won t have to ship multiple DLLs for different platforms Now the procedure l
223. ions can be used with Ruby s operator Download java_from_ruby special_cases rb java_import java util regex Pattern this copy is P1 0 printing Jan PASSING PARAMETERS simple_us_phone Pattern compile d 3 d 3 d 4 Call 503 555 1212 simple_us_phone gt 5 You can still match strings the Java way through the various methods of Pattern and Matcher But the Ruby syntax is much more convenient Collections If you re accustomed to indexing Ruby Array and Hash objects with the operator you ll find that the same technique works on Java Map and List objects as well Download java_from_ruby special_cases rb assume this came from some Java function java_list entries gt lock stock barrel first_item java_list 0 gt lock Moreover all Java Collection objects gain the traditional Ruby array operators lt lt length and join JRuby mixes the Ruby Enumerable interface into Java Collections and lterables So you can use Ruby s functional programming idioms directly on Java classes Download java_from_ruby special_cases rb assume this came from some Java function java_list_of_urls entries gt lt Java JavaNet URL Oxacecf3 gt lt Java JavaNet URL 0xf854bd gt protocols java_list_of_urls map do url url protocol end gt http ftp Java and Ruby each have a notion of Comparable objects Download java_from_ruby special_cases rb
224. is better quality in the shipping product Because of Ruby developers notorious passion for testing and because of programmers constant temptation to scratch one s own itch Ruby boasts an abundance of testing frameworks Which ones should you investigate We re going to walk the middle ground between showing you just our favorites and boring you with a laundry list of twenty dif ferent choices Test Unit The first framework most Ruby programmers encounter Test Unit is part of the Ruby standard library It is quite closely modeled on the original xUnit family of software including the JUnit framework for Java and as such doesn t use as many interesting Ruby features as some of the others do The main advantage of Test Unit is that it s available on all Ruby instal lations Because it doesn t use as many of Ruby s advanced features it s also quite straightforward to understand JRuby includes Test Unit and you can test Java code with it as easily as you can test Ruby The following example shows a simple test case that checks some prop erties of the java util HasnMap class in the Java core library We ve tried Report erratum 1 0 printing January 2011 RUBY TEST FRAMEWORKS lt 201 to use several different parts of Test Unit to give you a fair idea of the components in it Download testing_with_jruby test_unit hashmap rb require test unit require java java_import java util HashMa
225. itte SQL column You can use the same mapping mechanism to define associations among tables Download databases ribs_mappings rb blog belongs_to Owner blog has_one Layout name gt look blog has_n posts For this model we ve specified that every blog belongs to an owner This code will create an association named owner and will expect the wp_blog table to have a foreign key called owner_id You can change the name of this foreign key by providing a column parameter Next we ve declared that every blog has one layout accessible through the look property Ribs will expect there to be a column named blog_id on the layout table The has_n notation defines one to many relationships such as A blog has zero or more posts You can pass in a Ruby class name or as we ve done here for readability a plural noun These definitions will Report erratum 6 3 give you Hibernate associations between models and will create proxies to simplify working with these objects By default Ribs will just slurp in all your columns This might not be what you want especially if you have columns that are large or security sensitive The final two declarations in our class show how to deal with these situations Download databases ribs_mappings rb blog stats avoid blog auth avoid default gt abc Note that the default parameter allows you specify a default value for any skipped column This model has just one mapping
226. iving Java without having to bang our heads against the more obscure edge cases yet Download the latest jar for example iText 5 0 1 jar from the official site and copy it into the directory where you re following along in code Next add this snippet to a file called pdf_demo rb Download java_from_ruby pdf_demo rb require java pdf com itextpdf text Document new para com itextpdf text Paragraph new Brought to you by JRuby file java io FileOutputStream new pdf_demo pdf com itextpdf text pdf PdfWriter get_instance pdf file pdf open pdf add para pdf close In the spirit of walking before we run let s walk through the source before we run the program In the opening lines we create a few Java 6 The term impedance mismatch comes from electrical engineering It refers to the power lost to reflection when two circuits are connected It s also a poetic way to describe the conceptual losses between two different software domains 7 http sf net projects itext files Report erratum this copy is P1 0 printing January SEEING JAVA THROUGH RUBY GLASSES B pdf_demo pdf 1 page T we Brought to you by JRuby Figure 2 3 The generated PDF in all its glory objects the same way we d create Ruby ones by calling the class s new method We use a typical full package name for each class for example com itextodf text Document In JRuby Java methods look and act like Rub
227. k because it used to encourage quoting in Ruby instead of letting the database take care of it To prepare and use such a statement we use the prepare method like we did earlier Report this copy is P1 0 printing Janua RUBY DATABASE FRAMEWORKS lt 150 Download databases dbi_prepare rb require rubygems require dbi DBI connect DBI Jdbc mysq1 localhost using_jruby root driver gt com mysq jdbc Driver do dbh sth dbh prepare INSERT INTO blogs name author VALUES sth execute Architecture Richard Gabriel sth execute Physics Lee Smolin sth execute Memes Richard Dawkins sth finish end Here we prepare an INSERT statement and then run it with three differ ent pieces of data This technique is not limited to INSERTs of course You can use it with any kind of SQL statement DBI also allows you to get lots of metadata associated with a current connection result set or table This information is readily available from DBI s online documentation With these pieces in place you have everything you need to get started with DBI for low level database tasks Sequel Sequel is a relatively new database framework for Ruby It s quite dif ferent from both ActiveRecord and DBI sitting somewhere in between them on the ladder of abstraction It s closer to the database than ActiveRecord but more abstract than DBI You generally don t work with raw SQL comm
228. k mount 0 6 13 Using rack test 0 5 6 Using tzinfo 0 3 23 Using actionpack 3 0 1 Using mime types 1 16 Using polyglot 0 3 1 Using treetop 1 4 8 Using mail 2 2 7 Using actionmailer 3 0 1 Using arel 1 0 1 Using activerecord 3 0 1 Installing activerecord jdbc adapter 1 0 1 Using activeresource 3 0 1 Using bundler 1 0 2 Installing jdbc sqlite3 3 6 14 2 056 Using thor 0 14 3 Using railties 3 0 1 Using rails 3 0 1 Your bundle is complete Use bundle show gemname to see where a bundled gem is installed The beauty of having the dependencies stored in Gemfile is that you can ensure that anyone else working on your application has the same set of libraries Everyone simply needs to remember to run bundle install the first time or bundle update when someone changes the Gemfile Configuring the Database The next step after creating a new Rails application is to configure your database Open config database yml It will consist of three sections named after the three standard environments Rails creates for you this copy is P1 0 printing GOING ROUGE lt 4110 AA E Ola Says Be very careful when editing YAML files files that end in yml or yaml one single tab character in these files will render them unreadable to Ruby If you see strange errors after edit ing database yml check your whitespace for tabs test development and production Here s the setup fo
229. l ambiguous argument PASTA 28 lines of errors including things like at org jruby embed internal EmbedRubyObjectAdapterImp1 call at org jruby embed internal EmbedRubyObjectAdapterImp1 callMethod at org jruby embed ScriptingContainer callMethod at book embed Historian6 main Historian6 java 16 OK it got the job done but yuck Fortunately we can catch Ruby exceptions in Java using JRuby s InvokeFailedException Download ruby_from_java historian src book embed Historian7 java ScriptingContainer container new ScriptingContainer container setLoadPaths Arrays asList lib container runScriptlet require archive7 Object archive container runScriptletC Archive new try List lt GitDiff gt files List lt GitDiff gt container callMethod archive history new Revisions args 0 args 1 for GitDiff file files System out printInC FILE file getPath System out printiIn file getPatch catch InvokeFailedException e doSomethingSensibleWith e System out println Couldn t generate diff please see the log file this copy is P1 0 printing Jc THE NITTY GRITTY Here are the results bin historian7 PASTA NOODLES ruby_from_java historian lib git lib rb 700 in command git diff p PASTA NOODLES 2 gt amp 1 fatal ambiguous argument PASTA unknown revision or path not in the working tree Git GitExecuteError Use to separate
230. l shoulda and then run the Ruby file directly jruby hashmap_shoulda rb Loaded suite hashmap_shoulda Started Finished in 0 267 seconds 5 tests 5 assertions 5 failures 0 errors The output of running this code looks exactly the same as with Test Unit only the style of writing tests has changed Each individual test is a block passed to should rather than a method beginning with test_ And we ve used the context method to gather our tests into logical groups which can be nested The contexts lend their names to the generated test methods as you can see when you run the test suite with the v option jruby hashmap_shoulda rb v Loaded suite hashmap_shoulda Started test New hashmap should be empty HashMapTestCase test New hashmap should raise error on entryset iterator next test New hashmap with one entry should associate a value with a key test New hashmap with one entry should have size one HashMapTestCase test New hashmap with one entry should not be empty HashMapTestCase Finished in 0 264 seconds 5 tests 5 assertions 0 failures O errors One feature of Shoulda we re really fond of is the ease with which you can create custom macros reusable chunks of test code Imagine we wanted to test some of the other Map implementations in java util Since all of these classes share a common interface and even some common behavior with HashMap it would be nice to exercise them all
231. languages This chapter has provided a whirlwind tour of some of the better choices for working with databases from JRuby We first spent some time look ing at the different parts of ActiveRecord the most mature Ruby data base library and a good choice for many applications We also looked at DBI and Sequel to see how some of the existing Ruby libraries solve the task of database connectivity quite differently After looking at the pure Ruby libraries we moved on to Ribs and JDBC two options that are available only in JRuby It can sometimes be hard to pick one framework among all the different choices avail able but we hope that this chapter has shown you enough to make an informed decision for your project Of course you don t have to just choose one of these and stick with it Try them to see what fits best Be sure to reevaluate your choice as your application evolves Report erratum 7 1 Chapter 7 Over the previous few chapters we ve journeyed together through the process of writing software in JRuby We hope you ve had the chance to try some of the techniques on programs of your own Once you ve done the hard part of getting your code working packag ing it up and getting it onto the target computer should be a breeze right Well yes actually Both Ruby and Java have established build systems which developers have been relying on for years Over the next several pages we re going to see how these tools Rake
232. leaving the topic of testing Writing High Level Tests with Cucumber The first logical step upward from checking individual classes is wiring up several classes together and testing them as a group This is the focus of integration testing We ve seen how the RSpec framework and its cousins make it easy to write tests for Ruby and Java classes in a clear Ruby notation But even the most lucid programming language is still a programming language When youre writing about broader parts of the program your audience may include people outside your close knit circle of developers With that in mind the RSpec team created the Story Runner which allows you to write your tests in plain English This component has since spun off into a stand alone project Cucumber WRITING HIGH LEVEL TESTS WITH CUCUMBER lt 219 You might say that stories are the purest embodiment of BDD they help you focus on the app s behavior as a whole Cucumber separates the writing of a story from the implementations of the individual steps Programmers implement the steps in Ruby or Java and the whole team including nontechnical people can participate in writing and critiquing the overall stories To show you the flavor of Cucumber we ll write a small story about searching the Web In subsequent sections we ll hook this code up to a real browser and breathe life into this test Download beyond_unit_tests selenium search feature Feature Web search In
233. listener instead JRuby will take care of creating a listener class for you unless e value_is_adjusting F oooi end When the user changes the selection Swing may actually fire a stream of several events We have to test the event to make sure it s not in the middle of one of these streams If you feel surprised that Swing requires this kind of arcane knowledge just for a simple app you re not alone 4 For an explanation of adding methods to Ruby objects and classes at runtime see http ola bini blogspot com 2006 09 ruby singleton class html Download guis swing bookie rb new_index e source get_selected_index old_index e first_index e last_index find i i new_index The event object e has a first_Lindex and a last_index field One of them represents the previous selection and one the new selection but we can t know in advance which one is which We actually have to test them both against the result of get_selected_index Download guis swing bookie rb contents old_index edit text edit text contents new_index preview text RedCloth new edit text to_html This last bit saves away the old text and replaces the Edit pane with the new text It also updates the Preview pane with the HTML generated from RedCloth Now let s make a tab control for the Edit and Preview windows so that the user can toggle between them We do this by creating a JIabbedPane and adding the two windows to it Downl
234. llection classes Unless you re calling a Java library function expecting an ArrayList it s usually better just to use a Ruby Array instead But bear with us and try our slightly stilted example in jiro you should see something like this String List of Fixnum 3 Symbol assorted_items Now let s try something we couldn t have done in plain Ruby Let s hook into some Java platform specific functions and query a few properties of the JVM Download introduction jvm rb require java os java lang System get_property os name home java lang System get_property java home mem java lang Runtime get_runtime free_memory puts Running on os puts Java home is home puts mem bytes available in JVM Running on Mac OS X Java home is System Library Frameworks JavaVM framework Versions 1 5 0 Home 1592320 bytes available in JVM this copy is P1 0 printing WRAPPING UP As you can see we can access native Java classes such as java lang Runtime and java lang System using a dot notation similar to Java s import syntax One thing to note is that JRuby gives you the option of call ing Java functions like getProperty by more Ruby fitting names like get_property 1 8 Wrapping Up Now that you have JRuby installed and have taken it for a spin it s time to get some real work done In the upcoming chapters we ll tackle some of the most common ways people bring the Java and Ruby worlds together
235. log s collection of posts There are lots of ways of sticking together two associated objects For this case it makes sense just to call create on the associated posts collection and let ActiveRecord take care of the potentially tricky process of wiring them together A database mapping wouldn t be very useful if the only way to look up objects were through their IDs ActiveRecord models support a mind boggling number of ways to slice and dice data Here we re filtering blogs by author and then taking the first one that matches The docu mentation for ActiveRecord is full of examples of other techniques for searching through databases In the final line we delete the first Blog in the filtered list by calling destroy This will also make the instance immutable so if you try to modify any of the attributes of the instance after destroying it it will raise an exception This is really the minimum you need to know to be able to use ActiveRe cord models Armed with this information you should be able to add search for update or remove objects from your own databases In the next few sections we ll take a quick look at the other database libraries for Ruby and see how they compare While ActiveRecord is the premier Ruby database library there are times when one of the alternatives is a better fit DBI DBI is a very lightweight framework in that it tries to get really close to the database It is not a mapping framework like ActiveR
236. lp you in your own projects Finally we zoomed out to discuss the general trade offs among embedding approaches We hope this discussion has whet your appetite to introduce Ruby into your Java project In the next chapter we re going to take the next logical step and compile Ruby programs down to JVM bytecode 4 1 Chapter 4 By now you ve had the chance to run a few Ruby applications on the JVM You ve tried a few of the many Ruby libraries available in the wild You re probably becoming a whiz at calling from Ruby into Java and vice versa We hope you re getting the feel for how a JRuby application fits into the Java ecosystem and how you can start using it for your applications today Ready to take the next step toward JRuby mastery Compiler 101 A common theme in this book is that JRuby offers both sensible de faults and advanced control For quick scripts where you don t care what s going on under the hood you can just jump in and treat JRuby like a faster Ruby But when you have to plug into a legacy system or squeeze a little more performance into a complex system JRuby rewards further exploration The compiler is no exception JRuby ships with a compiler that s always looking for chances to optimize your code without any explicit instruc tions from you When the need arises you can override the defaults and tap into this power directly We ll talk about how this happens in a moment But first we need
237. lse If you d like to see a log of methods as they JIT you can enable this property 4 We should note that this feature is still a work in progress as of this writing Report erratum PROPERTIES lt d 307 jruby jit codeCache directory If you specify a codeCache directory JRuby will also save JITed meth ods to disk You can use this code cache in later runs to reduce the JIT ing cost or to ship pre JITed methods to one of those pesky restricted environments Configuring JRuby Features The next few settings deal with code execution jruby native enabled true false Normally JRuby uses several native libraries to provide specific bits of functionality For example lower level POSIX functions or C based extensions require us to be able to load native code On restricted envi ronments or in more secure server settings native libraries are often disallowed Specifying true for this property will turn off those native libraries and try to use pure Java equivalents as much as possible jruby compat version RUBY 1_8 RUBY 1_9 Like the 1 9 flag this property can be used to explicitly specify the compatibility mode The default is RUBY1_8 jruby objectspace enabled true false In C Ruby the ObjectSpace module provides access to various aspects of memory management For example ObjectSpace each_object makes it possible to walk through all objects in memory Because of the way the JVM works implementing t
238. lt 1 Thanks we ll see what we can do jruby takes a wide range of command line parameters to customize the way your programs run A full discussion is outside the scope of this chapter but it s worth talking about one of the more important ones Running Common Ruby Programs If you ve been coding Ruby for a while you re used to having certain tools available as executables such as gem and rake A typical Ruby program will install itself into your Ruby distribution s bin directory You may be tempted just to make sure JRuby s bin is at the front of your PATH and then run these commands directly just by typing in their names But it s best to invoke command line tools through JRuby rather than directly In particular Ruby s package manager RubyGems may not know whether to use plain Ruby or JRuby if you just type gem on the command line A much more reliable approach is to use Ruby s standard S option for launching stand alone scripts Instead of typing this gem install rspec you d type the following jruby S gem install rspec 11 For more information about this option see Appendix C on page 294 With all this talk of development environments what do we the authors use to write code for our JRuby projects By some strange cosmic coincidence four out of the five of us are heavy users of the Emacs text editor The odd man out hops between Vim and TextMate All three of these editors have
239. m install jruby rym use jruby If you re a long time RVM user you ll want to upgrade to the latest RVM version before using it to install JRuby From an Archive If you have a heavily customized setup or just like doing things your self you can get a zip or tar gz archive from the same download page Extract the archive somewhere convenient on your system such as C or opt You can run JRuby straight from its own bin subdirectory but you ll probably find it more convenient to add it to your PATH On UNIX including Mac OS X you can do the following export PATH PATH opt jruby bin On Windows you ll need to set both the PATH and JAVA_HOME variables C gt SET PATH PATH C jruby bin C gt SET JAVA_HOME C Program Files Java jdk1 5 0_19 You ll also need a recent version of the Java runtime at least version 1 5 6 5 http rvm beginrescueend com 6 http java com en download Report this copy is P1 0 printing Jan KICKING THE TIRES From Source Code If you re never satisfied with anything less than the latest features and bug fixes you may want to try your hand at building JRuby from source You ll need the following in addition to the Java runtime men tioned earlier e The Ant build system version 1 7 or newer e The Git source control system First grab the latest code with Git git clone git github com jruby jruby git Next jump into the jruby directory that just got created
240. make sure you name your new class Historian2 to match the file Download ruby_from_java historian src book embed Historian2 java ScriptingContainer container new ScriptingContainer container setLoadPaths Arrays asList lib String expr require git n outs Git open diffC HEADA HEAD container runScriptlet expr The call to setLoadPaths adds the project s lib directory to the scripting container s Ruby search path so that the require line in Ruby can find the git ro library Next we do a Git diff on our project home which happens to be a Git repository to see what has changed since the last commit Go ahead and run the new version of the app The results should look something like this bin historian2 diff git a lib archive8 rb b lib archive8 rb new file mode 100644 index 0000000 1d5967f dev null b lib archive8 rb 0 0 1 12 require git Our first real result Let s ride this momentum as we charge into some of the details of the embedding API Report this copy is P1 0 printing Jar A REAL LIFE EXAMPLE SOURCE CONTROL Passing Strings In and Out Ruby is still in charge of the output via its puts function Let s get rid of that call and just have our script return the result to Java as a string Download ruby_from_java historian src book embed Historian3 java ScriptingContainer container new ScriptingContainer container setLoadPa
241. mmon definitions and then describe them afterward Download databases ar_description rb require rubygems require active_record class Blog lt ActiveRecord Base set_table_name WP_BLOG set_primary_key blog_id belongs_to owner class_name gt Person has_one audit_log foreign_key gt watched_id I v has_many posts has_many authors through gt posts end RUBY DATABASE FRAMEWORKS lt 142 This code defines a Ruby model class named Blog sets the table name to WP_BLOG the default would have been blogs and sets the primary key to be blog_id instead of the default primary key of id We don t have to say anything at all about the blog s basic properties If for example the WP_BLOG table has a name a creator and a visit_count column each of these will automatically be accessible in Ruby with the same name it has in the database We see four different examples of associations in this code First let s look at belongs_to and has_one Each of these indicates a foreign key relationship In the case of belongs_to the foreign key will be a column called owner_id in this model s own WP_BLOG table The has_one declaration on the other hand shows that the watched_id foreign key lives in a separate audit_logs table and points back at this model As you can see ActiveRecord uses sensible naming conventions for column table and class names but allows you to override them The final two
242. mocks inside the test Download testing_with_jruby mocha hashmap_spec rb describe HashMap do it can be created from an empty Map do map Map new map expects size returns 0 iter Iterator new jter expects hasNext returns false set Set new set expects iterator returns iter map expects entrySet returns set HashMap new map size should 0 end end this copy is P1 0 printing WRAPPING UP lt 217 What have we gained apart from a syntax that s less likely to overflow our right margin For one thing Mocha isn t tied to one test frame work so you can reuse your knowledge in other frameworks Though it s beyond the scope of this example Mocha also has really sophisti cated argument checking tests Finally if you use JtestR discussed in Section 9 3 JtestR on page 229 Mocha allows you to mock concrete classes instead of just interfaces It s tempting to discuss how some of our other favorites like Schmock and FlexMock play in JRuby 9 But doing so wouldn t get us any fur ther along in this book s mission which is to shed light on how Java and Ruby interact So lets break camp here and move on to wider testing topics 8 4 Wrapping Up In this chapter we ve seen how Ruby s top notch unit test frameworks can seamlessly test Java code Since isolating the code under test is a key part of this process we ve also looked at a couple of mocking and stubbing libraries Ama
243. nally end this copy is P1 0 printing GETTING THE JOB DONE lt 4 289 As you can see we also used an ensure clause which Ruby will run no matter what exceptions are raised or rescued A 3 Getting the Job Done You ll eventually come into contact with most of the previous concepts as a natural part of working with Ruby But you may be wondering about specific getting started tasks such as writing text to the screen or loading code from another library So let s end this chapter on a light note and talk about these uses There are two methods that are most often used to display informa tion in Ruby The first one is called puts It calls to_s on its arguments effectively telling them Convert yourself to a string and then prints the resulting strings to standard output with each one followed by a newline puts slightly more verbose cousin p calls inspect on each argu ment Give me some details about yourself and prints the results to standard error Based on these definitions you ve probably deduced that puts is more useful for regular program output and p is more useful for debugging That covers a bare minimum of output how about input Ruby pro vides a method called gets which is the inverse of puts It waits until the user types in something ending in a newline and then returns the result Here s a small example of Ruby I O puts Welcome to my program What s your name name gets
244. nd task default gt jar create javadoc create As is the case with any Ruby function namespace has a return value a Rake NameSpace object We store our namespaces in the jar and javadoc variables so that we can refer to them later when we define our default task Cleanup and File Lists After our jar file finishes building we have no need for the intermedi ate class or Manifest files We could define our own cleanup task that deletes a bunch of hard coded filenames But once again Rake gives us a handy shortcut for cleanup the rake clean add on Download rake baseball rakelib clean rake require rake clean CLEAN include x class Manifest CLOBBER include jar doc this copy is P1 0 7 2 When you load this file Rake defines two new tasks clean and clobber plus two new lists for you to add filenames to When you run rake clean Rake will delete anything you ve add to the CLEAN list The even more destructive rake clobber deletes everything on both lists What s the difference between clean and clobber The first one is meant for deleting just the intermediate class and Manifest files and leaving your final jar intact clobber on the other hand deletes all generated files leaving you with only the source code in your project directory Behind the scenes CLEAN and CLOBBER are Rake FileList objects They act like arrays but they understand wildcards such as asterisks and can be
245. nd of number validates_length_of Checking the length of something can be done either by comparing to a maximum or by comparing to a range Anything that responds to the message length can be used so a String value works fine and so does an association validates_uniqueness_of This validation is a bit different in that it doesn t check any property of the value itself but instead makes sure that there is nothing else with the same value for that prop erty validates_inclusion_of If you want to make sure that a value is in a range of values you can use this validation You can give it any kind of object that has the include method so arrays and ranges both work fine validates_format_of You may sometimes find it necessary to check that a string field matches a specific format In this example we ve used an extremely simple regular expression to make sure that a string looks a little bit like an email address validates_each There are several ways to do custom validation The low level way is to override validate validate_on_create or val idate_on_update The better way is to just define a custom valida tion with validates_each With this approach you simply provide the names of the proper ties to be checked plus a block that actually does the testing The block gets three arguments the model instance under validation the name of the property that is being checked and the new value that is about to be inserted in
246. ne another See http java sun com products jndi 6 See your JNDI implementation s instructions for how to create and name this object 7 http api rubyonrails org classes ActiveRecord Base html this copy is P1 0 printing RUBY DATABASE FRAMEWORKS lt 139 Ola Says Migrations are so useful that offen use them outside the con text of Rails applications wnenever want to be able to make controlled changes to my database structure code that runs when you re creating your database for the first time or when youre rearranging it later as your app evolves A typical migration will create a new table to represent a new class you re adding to your program or add a column to an existing table Migrations can also run in reverse dropping tables when you need to roll back to a previous version of your code Migrations are named with a timestamp so that they run in the order in which you created them This sequencing allows you to grow your database organically If you need a table you add a new migration for it If you need a new column add a new migration to add that column It just so happens that most of the complexity in activerecord jdbc adapter lies in the code related to migrations The reason is that Data Definition Language DDL is the least specified part of SQL and all vendors have different ways of manipulating the database structure That said most standard databases work fine when combining migra ti
247. ne phase of our build For example we might want to do some copying or processing of resources to be included in a jar file during the generate resources phase but we might also want to use Rake to launch a custom testing framework during the test phase We ll write one execution for each phase of the build where we d like to use Rake Each execution declaration should have at least three parts an ID a phase and a goal Give your execution a unique ID to keep Maven happy and name the phase of the build where you want to attach the plug in A full list of phases appears in the Maven life cycle reference Specify rake in the goals goal section Download rake maven pom simple xml lt plugin gt lt executions gt lt execution gt lt id gt my custom resource step lt id gt lt phase gt generate resources lt phase gt lt goals gt lt goal gt rake lt goal gt lt goals gt lt execution gt lt executions gt lt plugin gt This setup assumes you have a companion Rakefile in the same direc tory as your pom xml and it contains a default Rake task Maven will invoke this task during the generate resources phase OK that s a pretty good start but let s say you want to do a little more than rely on defaults You can add a configuration section with one or more of these tags inside e script Rather than using an external Rakefile just embed your Rake tasks right inside pom xml rakefile Specify a Rakefile rather t
248. need to create this history yourself by doing a git init plus a few commits 2 Java already has a library for accessing Git repositories JGit But let s say you were itching to use one of the many Ruby bindings to Git instead 3 http repo or cz w rubygit git 4 http git scm com 5 http jruby org s3 amazonaws com downloads 1 5 5 jruby complete 1 5 5 jar 6 http wikijruby org DownloadAndBuildJRuby Report erratum P1 0 printing January 2 A REAL LIFE EXAMPLE SOURCE CONTROL As we proceed you ll notice that we re building up this project in stages from Historianl java up to Historian8 java You might find it slightly ironic that we re using such an old school naming convention with such an advanced revision control system We want the filenames on the printed pages of this book to be explicit about what stage of the process we re in We ll give instructions for building the project on the command line with Ant see Chapter 7 Building Software for Deployment on page 165 If you prefer the IDE experience we ve also included project files for NetBeans Getting the Two Worlds Talking Let s start with the basics Within the project structure we ve described create a file called Historian1 java in the src book embed folder Put the following imports at the top we won t need some of these classes until later but let s go ahead and import them now Download ruby_from_java historian src book embe
249. ng class that just happens to have a method called initialize which is the name Ruby uses for constructors Download java_from_ruby MethodClash java public class MethodClash public void initialize String data System out printInC Now we re set up with data Report erratum WRAPPING UP If you try to call this method the usual way JRuby will think you want the no argument Ruby initialize constructor Download java_from_ruby method_clash rb the_clash MethodClash new the_clash initialize everything gt 8 wrong of arguments 1 for 0 ArgumentError Actually we got lucky this time If the Java method had taken zero arguments instead of one Ruby would have silently called the wrong method instead of reporting an error Again java_send comes to the rescue Download java_from_ruby method_clash rb the_clash MethodClash new the_clash java_send initialize java lang String everything gt gt Now we re set up with everything Fortunately there are very few cases like this one object_id _id_ and __send__ come to mind but they are not likely to appear in a typical Java class Lost Monkeypatches JRuby lets you monkeypatch Java classes with a catch The Java side will be unaware of any new attributes or methods you define in Ruby In fact your additions will evaporate completely if Ruby lets go of all its references to the object The original Java part of the object will o
250. ng is for the programmers from Java land who prefer not to use any fancy Rubyisms beyond the ones they supply They are perfectly key_typed key_pressed key_released focus_gained focus_lost button_pressed and value_changed Report erratum 0 printing Jar WRAPPING UP lt 269 Tom Says In our complete Bookie example we have an additional scene called devtool with a single button labeled Refresh We used this scene as we wrote the example code Every time we tweaked our layout or styling we d click the button to update the bookie scene with the latest changes This was much faster than exiting and restarting the app To run Bookie with this debug helper enabled set the BOOKIE_DEV environment variable before launching BOOKIE_DEV 1 jruby S limelight open Adapting this tool to your own Limelight productions is easy just copy the code and point it at the scene you re developing It s a huge time saver happy developing their own ad hoc frameworks to suit their needs After all not invented here is a valid critique if the alternative is staring at an error log wondering which incantation will pacify a framework Rubeus is for those who want a little of Ruby s brevity to help cut out Swing boilerplate but who still feel comfortable with the Swing APIs They re fine with organizing the components and code for large projects on their own just as they did in Java Monkeybars provides answers
251. nistrator model Download introduction_to_rails output script generate scaffold txt jruby script rails g scaffold Administrator username string password string migration false skip invoke active_record identical app models administrator rb invoke test_unit identical test unit administrator_test rb identical test fixtures administrators yml route resources administrators this copy is P1 0 printing Jan RESTAURANT ADMINISTRATION 101 lt 119 invoke scaffold_controller create app controllers administrators_controller rb invoke erb create app views administrators create app views administrators index html erb create app views administrators edit html erb create app views administrators show html erb create app views administrators new html erb create app views administrators _form html erb invoke test_unit create test functional administrators_controller_test rb invoke helper create app helpers administrators_helper rb invoke test_unit create test unit helpers administrators_helper_test rb invoke stylesheets create public stylesheets scaffold css The migration false and skip options tell Rails that we ve already written the migrations for this model The username and password fields deter mine what goes into the generated HTML form Go ahead and start the web server using the script server command we saw earlier and visit htip localhost 3000 administrators in your browser Poke aro
252. nit_junit rb class TestUnitResultHandler private def add_fault fault case fault single_character_display when F result_handler add_failure current_test AssertionFai ledError new fault to_s when E result_handler add_error current_test java lang Throwable new fault to_s end end def test_started name current_test RubyTest new name result_handler start_test current_test end def test_finished name result_handler end_test current_test end end What s that RubyTest object we re creating inside test_started It s just a tiny Ruby class that implements the required methods from JUnit s org junit TestCase interface Download beyond_unit_tests junit_integration test_unit_junit rb class RubyTest lt TestCase def countTestCases 1 end def run result end def toString name end end Whew That s a lot of detailed API work to tie these two test frameworks together The good news is that it needs to be written only once You should be able to drop these two files into any JRuby project add some tests and run them with Ant Let s do that now PLUGGING INTO JAVA The Actual Tests Go ahead and drop a couple of _test ro files into the test directory For this example we ve copied the HashMap tests from the previous chapter into a file called test nashmap_test rb Download beyond_unit_tests junit_integration test hashmap_test rb require test unit require java java_import
253. nk of made an example in Rails once that was a database of Ruby scripts As one of the validations added a check to make sure that the Ruby script saved was actually valid Ruby code Download databases ar_validations rb require rubygems require active_record class Blog lt ActiveRecord Base validates_presence_of title message gt should be provided validates_numericality_of age only_integer gt true validates_length_of title in gt 5 35 validates_length_of posts maximum gt 30 validates_uniqueness_of title validates_inclusion_of blog_type in gt w work personal validates_format_of contact with gt A 4 validates_each title text do record attr value unless value buddha_nature record errors add attr doesn t have the Buddha nature end end end This example checks quite a lot of things on the Blog model Let s take them in order e validates_presence_of This method will make sure that the named attributes are not nil or blank All validations allow you to provide a custom message if you don t like the one provided and in this case an error message would say title should be provided this copy is P1 0 printing RUBY DATABASE FRAMEWORKS lt 144 validates_numericality_of As the name says it checks that an attri bute is a number You can decide if any kind of number is fine or if you only want to allow integers The default is to allow any ki
254. not likely to have Ruby or any gems on it You ll need to put Hpricot somewhere in the final product where scrape rb can find it Following common Ruby prac tice we ll install a private copy of Hpricot to a vendor subdirectory of our project for later inclusion in the build Download rake scrape Rakefile directory vendor desc Install Ruby gems into vendor task install_gems gt vendor do sh jruby S gem install i vendor hpricot end With that in place we re ready to build the jar A Minimal jar Recall that a jar file is basically a renamed zip file that follows a few con ventions The convention that interests us here is the Manifest which contains among other things the name of the Java class to run when the user launches the jar Notice that we said Java class Alas there s no direct way to give the name of a Ruby class instead If you ve been following along with the embedding chapter you re prob ably thinking Why not just write a tiny Java program that uses the JRuby embedding API to launch the main Ruby class from inside the jar You re right that s exactly what we re going to do Download rake scrape Launcher java import org jruby embed ScriptingContainer public class Launcher public static void main String args ScriptingContainer container new ScriptingContainer container runScriptlet require scrape PACKAGING FOR DEPLOYMENT lt 186 We ve alre
255. nternet love ins and flame fests So maybe it was inevitable that someone would try to combine the two JRuby is an implementation of the Ruby programming language written in 100 percent Java Why JRuby JRuby is just another Ruby interpreter It runs the same Ruby code you ve been writing all along But it s also a better Ruby interpreter You get true multithreading that can use all your computer s cores from one process plus a virtual machine that s been tuned for a decade and a half All of this book s authors have seen our Ruby programs speed up just by moving them to JRuby JRuby is also just another jar file You don t need to install anything on your Java workstation to try it And you don t need to do anything special to deploy your Ruby code to your production server Just hand your sysadmin a jar like you always do and they might not even notice you used Ruby except that you delivered your app in half the time and encountered fewer bugs down the road WHAT S IN THIS BOOK bt lan Says Ruby in Real Lif At work we needed to sift through a mound of engineering data Ruby was a natural fit for this task and we had working code in minutes But sharing this program with colleagues was a different story With regular Ruby we ran into trouble getting the code from one machine to another even though they were both run ning Windows XP We had to direct people to install a particu lar outdated version of MySQ
256. oad guis swing bookie rb tabbed_pane JTabbedPane new JTabbedPane TOP JTabbedPane SCROLL_TAB_LAYOUT tabbed_pane add_tab Edit edit tabbed_pane add_tab Preview preview tabbed_pane add_change_listener do event if tabbed_pane selected_component preview preview text RedCloth new edit text to_html end end Notice that this control also gets an event listener When the user switches to the Preview window we want to regenerate the HTML in case they ve modified the chapter Download guis swing bookie rb split_pane JSplitPane new JSplitPane HORIZONTAL_SPLIT split_pane add chapters split_pane add tabbed_pane The previous code creates a split pane with the chapter list on one side and the Edit Preview windows on the other Download guis swing bookie rb button javax swing JButton new Add Chapter button size Dimension new 40 40 button add_action_listener chapters add_chapter this copy is P1 0 printing RUBEUS lt q 246 10 3 When the user clicks the Add Chapter button the block we supply here gets called Like the other listeners this block has access to the chapters list control which is a local variable that we defined outside the block The final step is to create a top level window or JFrame to hold every thing else Download guis swing bookie rb frame JFrame new Bookie frame size Dimension new 500 300 frame layout BoxLayout new frame content_pane BoxLayout
257. ode history viewer in Java The program let s call it Historian will use a Ruby library to peer into a Git repository and print patches In a deli cious bit of recursion we ll view the history of Historian s own source code Setting Up Your Workspace Before we get started let s quickly examine the layout of the Historian project You can create this structure from scratch but we strongly recommend following along with the book s source code src book embed contains the Java source to our program which is what we ll be spending most of our time looking at lib contains the Ruby glue code we ll write to connect the Java world to the Ruby library we re wrapping lib git ro and lib git comprise a local copy of a popular Ruby Git library This library requires you to have Git installed on your system so grab that if you don t already have it bin get jruby liobs downloads jruby completejar a bundle containing the parts of JRuby needed by our Java program into the lib direc tory You ll need to run this script once at the beginning of the project or build your own jar from source bin make history sets up a new Git repository in the current direc tory and adds a couple of revisions for Historian to play with As with the previous script you should run this once before you dive into the code git contains the history of the project s own source code If you re creating this project from scratch you ll
258. oduction chapter_contents each do chapter_model this copy is P1 0 printing Januc APPENDIX F LIMELIGHT EXAMPLE SOURCE chapter text gt chapter_model title model gt chapter_model tid gt chapter_ chapter_model title end end update_selection end def update_selection selected scene dual_pane current_chapter select selected title if selected end def select chapter click_mouse false children each prop prop deselect chapter scene find chapter_ chapter if chapter chapter select chapter mouse_clicked nil if click_mouse end end end Download guis limelight bookie bookie players dual_pane rb module DualPane attr_reader current_chapter def update_preview_pane preview_content RedCloth new current_chapter text to_htm preview_content gsub lt br s gt n scene preview_pane text preview_content end def current_chapter chapter save current_chapter chapter scene find chapter_ current_chapter title select scene edit_pane text current_chapter text update_preview_pane scene chapter_list update_selection end def edit scene preview_pane style height 0 scene edit_pane style height 90 scene edit_pane style background_color sky_blue scene preview_tab style background_color white scene edit_tab style background_color sky_blue end APPENDIX F LIMELIGHT EXAMPLE SOURCE def preview save update_preview_pane sc
259. of DiffFiles which are now also Java GitDiffs Recall from Section 2 5 Arrays on page 46 that Ruby Arrays are also java util List instances Together these two facts mean that our return value is now castable to List lt GitDiff gt Here s how the Java code will process the results now Download ruby_from_java historian src book embed Historian5 java ScriptingContainer container new ScriptingContainer container setLoadPaths Arrays asList lib container runScriptletC require archive5 container putC revisions new Revisions args 0 args 1 List lt GitDiff gt files List lt GitDiff gt container runScriptlet history this copy is P1 0 printing A REAL LIFE EXAMPLE SOURCE CONTROL for GitDiff file files System out printInC FILE file getPathQ System out printiIn file getPatch Cool One cast and we are using the result like any other POJO Notice the sequence we re using now stash the input arguments in a global and then call a top level function that takes no parameters That may do for BASIC programs written in the 1980s but Ruby provides better abstractions Let s pass the revision information into history as a parameter instead of using a global While we re at it well move the function into a class Download ruby_from_java historian lib archive rb require git class Git Diff DiffFile include Java book embed GitDiff end class Archive def history
260. of the IDE and have everything you need to start coding With NetBeans you can do some of the many things in Ruby that you re used to doing in less dynamic languages automatically com pleting code stepping through a program in a debugger designing a GUI and performing simple refactorings 13 http www netbeans org Report erratum this copy is P1 0 printing Janua THE COMPILER Because NetBeans is cross language its level of Ruby specific integra tion is not quite as deep or polished as RubyMine s But it s a close second 1 6 The Compiler Throughout most of this book we re going to run JRuby programs the same way people run programs in plain Ruby hand the text of the pro gram over to an interpreter The interpreter walks through the program piece by piece translating and running code as it encounters it If you spend time in the Java universe you re probably wondering whether JRuby allows you to compile your Ruby code into class files up front and treat them like compiled Java code The answer is yes Here s how you d compile the previous example jrubyc example rb Compiling example rb to class example The compiler supplies a main method for you so you can now run the program straight from the java command adjust the path here to point to your JRuby installation java cp opt jruby lib jruby jar example Note that your compiled program still depends on some JRuby defined suppo
261. ong OverloadDemo what_type_is Fun gt string OverloadDemo what_type_is Hash new gt object Sometimes though things get a little hairier In the following Java class the overloaded methods both take integer types Download java_from_ruby HowManyBits java public class HowManyBits public int neededFor int i return 32 public int neededFor long 1 return 64 this copy is P1 0 printing CALLING OVERLOADED METHODS When we try to call the version that takes a 32 bit integer JRuby ends up promoting our parameter to a long instead Download java_from_ruby how_many_bits rb bits HowManyBits new bits needed_for 1_000_000 gt 64 How do we tell JRuby No I really mean the int version Forcing a Specific Overload In Java you can choose which overload you want by casting arguments to specific types For instance you might use System out printin char 70 to call the version of printin that takes a character rather than the one that takes an int But Ruby has no casting syntax are we stuck For tunately not We can use JRuby s java_send method to specify the int version of the neededFor method from earlier Download java_from_ruby how_many_bits rb bits java_send neededFor Java int 1_000_000 gt 32 If you ve used Ruby s built in send method the notation should look familiar Notice that this is a bit more cumbersome than a plain method call For this
262. ons and JDBC Let s take a look at an example migration Rails uses a structure of one file per migration and that works really well But if you want to do something ad hoc or maybe just see how migrations work in a code example it s fine to put several migrations in one file as in the upcom ing example Report erratum RUBY DATABASE FRAMEWORKS Assuming you have an establish_connection call at the beginning of your file as we ve discussed on the previous pages you can define a series of migrations like this Download databases ar_migrations rb class AddFooTable lt ActiveRecord Migration def self up create_table foo do t t string foo t text ibar t integer qux end end def self down drop_table foo end end class AddBlechColumnTable lt ActiveRecord Migration def self up add_column foo flax string end def self down remove_column foo flax end end Once you ve defined your migrations you can run them normally up or in reverse down Download databases ar_migrations rb AddFooTable migrate up AddBlechColumnTable migrate up AddBlechColumnTable migrate down AddFooTable migrate down The code will generate simple output like this provided everything was configured correctly Behind the scenes your SQL database will contain the new tables and columns jruby ar_migrations rb Addroolable niQRatl tg S s ssss s ss se Sasa See ee a ae create_table foo
263. ooks something more like this 1 Copy jruby complete jar and a bunch of rb files onto the target machine So you can reduce a bunch of hemming and hawing over version num bers and DLLs into a few simple file copies For desktop programs this means handing users a zip file which they can extract and run with a single command java jar jruby complete jar my_program rb For web apps you just scp a directory of source files up to the server or use a tool like Capistrano to do the copying for you Java Archives Although these approaches remove the risk and heartache of Ruby deployment they still expose Ruby filenames and directory structures 3 http www capify org Report erratum 0 printing January 2011 PACKAGING FOR DEPLOYMENT lt 184 to the owner of the target machine Wouldn t it be nice to use a mech anism Java developers are already familiar with like jar files Fortu nately you can The App We re going to build a tiny program that nonetheless has a couple of the same kinds of dependencies external Ruby libraries and compiled code that real world projects do Specifically we re going to do a bit of web scraping with the Hpricot library which uses a mix of Ruby and Java code Go ahead and install Hpricot first jruby S gem install hpricot Now let s write a small program that uses the library to get a list of recent books published by the Pragmatic Programmers Create a n
264. open http www yahoo com end When AI search for C A do term browser type p term browser click search submit browser wait_for_page_to_load 10 end Then Athe page title should begin with A J do title browser get_title 0 title length should title end Behind the scenes calls like click or wait_for_browser_to_load are sending instructions to the selenium server which is in turn controlling Firefox The Sbrowser global is an instance of Selenium SeleniumDriver It repre sents a connection we need to set up before the first test step runs and tear down after the last one completes In Cucumber this kind of setup code goes in a file called support env rb Download beyond_unit_tests selenium support env rb require selenium browser Selenium SeleniumDriver newC Jocalhost 4444 firefox http www yahoo com 15000 browser start at_exit browser stop To run a stand alone Cucumber test just pass the feature name to the cucumber command jruby S cucumber search feature this copy is P1 0 printing ACCEPTANCE TESTING Selenium s API calls are easy to write if not quite idiomatic Ruby They re also fairly easy to run though they do require the extra step of starting a separate server Watir Since it was created just for Ruby writing Watir code feels more natural in a Ruby project Watir also uses a more direct technique for control ling the brows
265. ops rob is spartan and its code in styles ro only defines its look Where is its behavior Limelight organizes player behavior in a scene s players directory The convention is one file per player with one Ruby module inside it both of them named after the player For instance the behavior for the Add Chapter player goes into the AddChapter module defined in players add_chapter rb Download guis limelight bookie bookie players add_chapter rb module AddChapter def mouse_clicked e contents production chapter_contents title contents length 1 to_s new_content title gt title text gt contents lt lt new_content scene chapter_list repopulate end end There is only one method in here mouse_clicked You don t have to do anything special to hook this code up to the mouse Limelight knows to look for it by name These kinds of implicit callbacks make reacting to user input a snap even for custom components 9 Limelight supports this style for several other events including mouse_clicked mouse_entered mouse_exited mouse_pressed mouse_released mouse_dragged mouse_moved Report erratum 0 printing Jar lt q 267 WRAPPING UP At the end of the callback we find the bookie scene and tell its chap ter_list prop to repopulate itself with the updated chapter contents Sometimes you have behavior that is common to more than one prop For example both the Edit and Preview buttons need to
266. or messages jruby J cp derby jar ribs_use rb Now we ll execute some raw SQL This practice is not recommended for day to day operation but can be useful for creating tables adding data in batch form and so on The following code will create a new table add some rows and then print the result of a SELECT Download databases ribs_use rb Ribs with_handle do h h dd1l DROP TABLE book rescue nil hoeddl lt lt SQL CREATE TABLE book id INT NOT NULL GENERATED BY DEFAULT AS IDENTITY CSTART WITH 1 INCREMENT BY 1 title VARCHAR 255 NOT NULL author VARCHAR 255 NOT NULL PRIMARY KEY id SQL stmt INSERT INTO book title author VALUES h insert stmt To Say Nothing Of The Dog Connie Willis A Confederacy Of Dunces John Kennedy Toole Ender s Game Orson Scott Card p h select SELECT FROM book end This code uses a database handle to manipulate the table structure Only low level Ribs calls require a handle We use the handle s ddl method to execute SQL queries We remove and then create a table of this copy is P1 0 printing books and then we use a prepared statement to insert three rows of data Finally we extract the data with a simple SELECT statement So far this looks more or less the same as the DBI database code The main difference is that it s Hibernate doing all the work Ribs is easiest to use when you follow its conventions In the simplest case you
267. or debugging or profiling scripts that use Kernel set_trace_func to track execution events like calls and exceptions If you want to use set_trace_func at all you should pass debug ng and ng server Running any JRuby program means waiting for the JVM to start For long running processes like web servers this brief delay doesn t matter But for quick shell scripts that you run over and over again even the shortest pause becomes annoying Report erratum COMMAND LINE OPTIONS lt 299 The Nailgun project is designed to let any Java based project take an end run around the JVM startup time It works by starting one in stance of the JVM in the background and then using a fast C client to connect to it JRuby comes with Nailgun To use it just start a server and leave it running jruby ng server Then pass the ng flag to JRuby jruby ng e puts Hello from Nailgun Before using Nailgun for the first time you ll have to compile the C client except on Windows where JRuby comes with a precompiled client Fortunately this step takes only a few seconds From JRuby s tool nailgun subdirectory type the following configure amp amp make There are a few interesting interactions between Nailgun and long running JRuby programs So we recommend you stick with the tra ditional launcher for servers daemons and GUI programs and use Nailgun just for quick shell scripts x optional directory
268. orm JIT compilation only as code becomes hot in other words gets called frequently This approach can speed up application startup It can also boost performance down the road because the compiler can use live runtime information to make optimization decisions JRuby includes a JIT compiler that optimizes your application as it executes Later we ll see how to make the most of its power Ahead of Time Compilation If you ve ever manually run a compiler against a piece of source code to create an executable file you ve performed ahead of time AOT com pilation AOT compilers often represent the first phases of a program s life cycle especially if the program s source code form is not generally executable on its own as is the case for languages like C or Java Most Ruby implementations including the standard implementation do not incorporate AOT compilers into their life cycle Instead they either walk through an AST at runtime as Ruby 1 8 does or run a lower level intermediate form of the code as Ruby 1 9 does AOT compilers often do less to optimize code than their JIT cousins since they can only use information available at compile time They are Report erratum 0 printing Janu COMPILER 101 useful for languages that don t have interpreters or that need to expose a standard compiled form to other libraries and languages They are also sometimes used for code obfuscation since the compiled form
269. orm waveform_with_sigs rb require java class Waveform java_signature Waveform double points def initialize points points points end java_signature double rms def rms raise No points unless points length gt 0 squares points map p p p sum squares inject s p s p mean sum squares length Math sqrt mean end end At this point you could retry the compilation step from earlier by run ning jrubyc java to generate a java file and then running javac to com pile that to a class Or you could combine the two steps into one The javac option will compile the generated Java code for you jrubyc javac waveform rb Generating Java class Waveform to Waveform java javac d cp jruby jar Waveform java this copy is P1 0 printing A SIMPLE COMPILED EXAMPLE a Charlie Says Filenames and Case Sensitivity 22222 The java_require directive has an interesting quirk on non case sensitive file systems the default on Mac and Windows These systems can t tell the difference between Waveform class which is a generated Java wrapper around Ruby code and wave form class which is just compiled Ruby code When some piece of Ruby code tries to require waveform JRuby will try to load Waveform class instead which will throw an error The solution to this is easy make sure your generated Java class has a different name than your Ruby source file For example
270. ou d type rake war war_staging which would create both rouge war as well as rouge staging war Another useful feature of Warbler is the executable war command This adds Winstone a small 166KB Java web server to the resulting war file To use it you run the executable task first and then the war task Download rake sessions warble_executable txt jruby S warble executable war rm f rouge war Creating rouge war Now you can run your web app on its own without needing a separate Java server Download rake sessions war_execute txt java jar rouge war Winstone 2010 05 19 00 00 07 Beginning extraction from war file Winstone 2010 05 19 00 00 07 WARNING The Servlet 2 4 2 5 spec XSD wa Winstone 2010 05 19 00 00 07 No webapp classes folder found privat webapp 2010 05 19 00 00 10 Info using runtime pool timeout of 30 seconds webapp 2010 05 19 00 00 10 Warning no min runtimes specified webapp 2010 05 19 00 00 10 Warning no max runtimes specified 11 http github com sbecker asset_packager 12 http winstone sourceforge net this copy is P1 0 printing WRAPPING UP lt 4 198 Winstone 2010 05 19 00 00 10 HTTP Listener started port 8080 Winstone 2010 05 19 00 00 10 Listener winstone ajp13 Ajp13Listener no Winstone 2010 05 19 00 00 10 Listener winstone ssl HttpsListener not Winstone 2010 05 19 00 00 10 Winstone Servlet Engine v0 9 10 running Once
271. ou can use something like the following Download databases jdbc_connect rb require java java_import java sql DriverManager DriverManager register_driver com mysql jdbc Driver new begin url jdbc mysq localhost using_jruby conn DriverManager get_connection url root ensure conn close rescue nil end Even this low level code looks a bit simpler than the equivalent Java code The lack of types make it quite readable The next step would be to get some data out of the database Download databases jdbc_select rb require java java_import java sql DriverManager DriverManager register_driver com mysql jdbc Driver new begin url jdbc mysq localhost using_jruby conn DriverManager get_connection url root stmt conn create_statement rs stmt execute_query SELECT FROM book while rs next p rs get_int 1 rs get_string 2 rs get_string 3 end ensure rs close rescue nil stmt close rescue nil conn close rescue nil end Of course this little piece of code makes it obvious that it would be nice to have some Ruby sugar on top of the Java ResultSet r Shohei Tan So let s make a new version Download databases jdbc_select2 rb require java java_import java sql DriverManager java_import java sql ResultSet DriverManager register_driver com mysql jdbc Driver new module ResultSet include Enumerable def each count self meta_data column_count while self next
272. ou don t provide an argument the default target Report erratum is executed Of course if there s no default target and you don t specify one then nothing gets run Rake with Ant So far we ve had a taste of how easy Rake makes scripting builds and we ve seen the power of calling portable Ant tasks from a Ruby environment Now let s bring Rake and Ant together by revisiting our Baseball example We ll see how mixing in a little Ant can improve the project If you re unfamiliar with Ant you might want to have the Ant user manual handy as you put it to use and discover the myriad tasks that are available One of the problems with using Make like rules to compile java files is that there are many more Java source files in a typical project Spawning the Java compiler individually on every file is inefficient So although our Rake rule for compiling the Pitcher and Catcher classes is clever it won t scale up well The Ant javac task is ideally suited for compiling Java sources Let s put it to use in our Rakefile in a task called ant compile Download rake baseball rakelib ant_compile rake require ant namespace ant do task compile do ant javac srcdir gt end end As we can see the javac task has some smart defaults built in to look for java files We can compile more files with less code than we did before Download rake sessions ant_compile ixt jruby S rake ant compile Cin code rake
273. ould certainly be possible to write a build script see Chapter 7 Building Software for Deployment on page 165 to search recursively through your project directory for source files and compile each one individually But there s an easier way As an alternative to passing a single rb filename to jrubyc you can pass a directory name If you couple this technique with the t option and a target directory JRuby will make the compiled Java package names mirror the directory structure of the Ruby source In other words if you have com example gui rb and com example data base rb and you type the following jrubyc t build then the resulting gui and database classes will be part of the com ex ample package Hiding the Source Many JRuby users simply want to compile their ro files to hide the source code In simple cases the simple jrubyc command works fine for this purpose It takes rb source files and outputs class files either in their own dedicated location or alongside the rb files In JRuby the require foo method will load either foo rb or foo class So you can usually just leave the rb files out of your deployment and run entirely from classes Avoiding Name Clashes On a bigger project you may run into a few issues with running from class files The hairiest of these is the difference between the way Ruby loads code by looking for rb files and the way Java loads code by look ing for classes wh
274. p class HashMapTestCase lt Test Unit TestCase def setup map HashMap new end def test_new_hashmap_is_empty assert map isEmpty end def test_hashmap_with_entry_is_not_empty map putC hello world assert map isEmpty end def test_value_is_associated_with_added_key map putC hello world assert_equal world map get hello end def test_entry_set_iterator_next_raises_error_for_empty_hashmap assert_raises NativeException do G map entrySet iterator next end end end You can run the code with this command jruby hashmap rb Loaded suite hashmap Started Finished in 0 029 seconds 4 tests 4 assertions 0 failures O errors There are several things going on here let s look at them one by one First we create a new test case by defining a class that inherits from Test Unit TestCase Then we define the setup method which runs before this copy is P1 0 printir RUBY TEST FRAMEWORKS lt 202 each test method much as its counterpart does in JUnit and other frameworks Finally we define the tests themselves Every method whose name begins with test_ will be run as a test by Test Unit Each test method is stand alone and depends only on the setup method for its preconditions and invariants Like most frameworks in the xUnit lineage Test Unit allows you to test your code using several different assertions The most common ones are assert assert_equal and assert_raises The gen
275. pdates the database say to drop or create a table you can call the do method on the database handle RUBY DATABASE FRAMEWORKS lt 148 Download databases dbi_table rb require rubygems require dbi DBI connect DBI Jdbc mysq1 localhost using_jruby root driver gt com mysq l jdbc Driver do dbh dbh do DROP TABLE IF EXISTS blogs dbh do lt lt SQL CREATE TABLE blogs id INT UNSIGNED NOT NULL AUTO_INCREMENT name VARCHAR 255 author VARCHAR 255 PRIMARY KEY id SQL dbh do lt lt SQL INSERT INTO blogs name author VALUES C Languages Ola Bini C Politics Roy Singham C Environment Al Gore SQL end This code will drop the table if it exists and then create the table from scratch and add some data to it The do method will return the number of updated rows after the command has finished This can be useful when checking whether an UPDATE statement actually did something for example Note that we re using the Ruby heredoc syntax to make the SQL statements more readable We re going to show a few more examples on how to use DBI As you will see DBI is actually much closer to JDBC than any of the other database tools described in this chapter When you extract values from the database DBI doesn t automatically give you back everything in one collection instead you get a handle to a result set so you can traverse the results in any way you want There ar
276. perator to append the new object to our list but only if it s valid note the trailing if expression Here s how you might use the code from this project ola Person new The following locators get added because they re in the right format ola add_phone_number 555 231 4555 ola add_address 1 Did It My Way The following locator gets ignored because it s not a valid US phone number ola add_phone_number 42 We have deliberately written this code with a variety of punctuation choices Some method definitions or calls have parentheses and some don t Some strings use single quotes and others use double quotes Ruby s flexible syntax allows you to use whichever style suits your pro gram best Defining and Calling Methods We ve seen a couple of method definitions already Lets dive a little deeper into the subject Class Methods So far we ve only seen instance methods methods that act on a single instance of an object What about static methods which belong to the entire class instead of one object Doesn t Ruby have those Yes and no Ruby has something that looks and acts similar to Java s static methods It s called a class method There are multiple ways to define one but the most popular ways are to name it self method_name or ClassName method_name Report erratum 0 printing Jar A CLOSER LOOK 279 Here s how those two styles would look for defining something like a f
277. ple_ant_test gt lt description gt Simple example Ant project for jtestr lt description gt lt taskdef name jtestr classname org jtestr ant JtestRAntRunner classpath Jib jtestr jar gt lt taskdef name jtestr server classname org jtestr ant JtestRAntServer Classpath Jib jtestr jar gt lt target name test description Runs all tests gt lt jtestr gt lt target gt lt target name test server description Starts test server gt lt jtestr server runtimes 3 gt lt target gt lt project gt This file gives you two new build targets test and test server To use them first open a new console window and run ant test server there Leave that running and then use the test target as usual By default JtestR assumes your tests are in the test directory but you can adapt this setting to your project this copy is P1 0 printing Jai lt 4 230 PLUGGING INTO JAVA A minimal Maven 2 POM for JtestR would look like this Download beyond_unit_tests jtestr pom xml lt xml version 1 0 encoding utf 8 gt lt project gt lt modelVersion gt 4 0 0 lt modelVersion gt lt groupId gt org jtestr lt groupId gt lt artifactId gt jtestr maven example lt artifactId gt lt packaging gt jar lt packaging gt lt version gt 0 1 lt version gt lt name gt JtestR Maven Example lt name gt lt build gt lt directory gt target lt directory gt lt outputDirectory gt target classe
278. port java lang StringBuffer The latter is handy for importing a bunch of similarly named packages together Download java_from_ruby loading_classes rb Frame Dialog Button each do name java_import org netbeans jemmy operators J name Operator end You can also pass a block to java_import in case you need to do some thing else to the package name such as renaming it to avoid a conflict with some existing Ruby class Download java_from_ruby loading_classes rb java_import java lang String do pkg cls puts cls lives in pkg IString don t clobber Ruby s String class end You may encounter code in the wild that uses the shorter import alias We recommend sticking with java_import to avoid conflicts with libraries such as Rake that define their own import method Finally we can move on to actually calling external code this copy is P1 0 printing Jal USING OBJECTS 2 4 Using Objects It s taken a bit of housekeeping to get to this point We ve had to find libraries load classes and resolve names Now comes the payoff driv ing a Java object from Ruby Static Methods Let s start with the easiest kind of Java method to invoke static meth ods Since these aren t attached to any particular class instance we can punt on the whole issue of object creation for now You can calla static Java method directly from JRuby Download java_from_ruby static rb java_import java lang System
279. proaches to help you tackle any bug with confidence These secrets of professional debugging illuminate every stage of the bug life cycle from constructing software that makes debugging easy through bug detection reproduction and diagnosis to rolling out your eventual fix Learn better debugging whether youre writing Java or assembly language targeting servers or embedded micro controllers or using agile or traditional approaches Debug It Find Repair and Prevent Bugs in Your Code Paul Butcher 232 pages ISBN 978 1 9343562 8 9 34 95 http pragprog com titles pbdp The Pre amatic fogrammers Driving Technical Change Why People On Your Team Don t Act on Good Ideas and How To Convince Them They Should Terrence Ryan Edited by Jacquelyn Carter Find Repair P amp Prevent Bugs in Your Code Paul Butcher ae ed by Soc Carter The Pragmatic Bookshelf features books written by developers for developers The titles continue the well known Pragmatic Programmer style and continue to garner awards and rave reviews As development gets more and more difficult the Pragmatic Programmers will be there with more titles and products to help you stay on top of your game Visit Us Online http pragprog com titles jruby Source code from this book errata and other resources Come give us feedback too Register for Updates http pragprog com updates Be notified when updates and new book
280. puts Slicing the bread end desc Only the finest Emmentaler for our sandwich task cheese do puts Grating the cheese end Sure the notation is clearer But there s much more going on here than just syntax You have the entire power of the Ruby environment at your disposal should you need it Conditional expressions loops functions classes libraries you name it And of course with JRuby you have the reach of the Java platform as well Getting Started with Rake If you re coming to JRuby from Java you ll find that the procedure for kicking off a build with Rake is similar to what you ve used with Ant The rake command looks in the current directory for a Rakefile a description of the tasks that can be performed here If you name your file Rakefile Rakefile ro or a lowercase version of either of those Rake will find it automatically When you encounter a new Rakefile it s a good idea to get the lay of the land by running rake first with the T option This prints out a list of top level tasks Report erratum 0 printing Jar Download rake sessions rake_tasks txt jruby S rake T Cin code rake sandwich rake bread I guess sliced bread really is the greatest thing rake cheese Only the finest Emmentaler for our sandwich rake sandwich Make a tasty lunch Notice how Rake helpfully prints each task s description alongside it These came from the Rakefile in the lines beginning with des
281. quest_with_http_basic do user_name password Administrator find_by_username_and_password user_name password end end end Notice the before_filter declaration With this in place Rails will call our authenticate method before any action on an AuthenticatedController or on one of its subclasses Inside authenticate we check for any HTTP Basic Authentication credentials and look for a matching administrator account The final step is to make all three controllers inherit from AuthenticatedController instead of ActionController For example the first line of app controllers administrators_controller ro should look like this class AdministratorsController lt AuthenticatedController At this point we have a utilitarian but working administrative user interface in place One thing we can do to spruce things up a little bit is add a common link bar for the administration options Open the three controller files back up and on the second line of each add this line of code layout authenticated Then add a new file called app views layouts authenticated html ero with the following Download introduction_to_rails rouge app views layouts authenticated html erb lt DOCTYPE html gt lt html gt lt head gt lt title gt Administration lt title gt lt stylesheet_link_tag all gt lt javascript_include_tag defaults gt lt csrf_meta_tag gt lt head gt lt body gt this copy is P1 0 printing OPEN
282. r truncated listing WEB INF WEB INF app WEB INF config WEB INF gems WEB INF 1ib WEB INF 1ib jruby core 1 5 WEB INF 1ib jruby rack 1 0 1 j WEB INF 1ib jruby stdlib 1 WEB INF 1og WEB INF tmp WEB INF vendor images javascripts stylesheets As you can see the Rails application code and directory structure gets stashed below the WEB INF directory in the archive and the images stylesheets and javascripts directories get promoted to the document root Warbler also tries to figure out what Ruby gems your application uses and then creates an embedded gem repository for you in WEB INF gems Most importantly Warbler bundles a copy of JRuby as jar libraries as well as JRuby Rack a small bridge from the Java Servlet API to Ruby s Rack API To the Java server our Rails application looks just like any other Java Servlet Let s go ahead and deploy this file to a Java application server Two pop ular open source servers are Apache Tomcat and GlassFish 6 http github com nicksieger jruby rack See also http java sun com products serviet and http rack rubyforge org 7 http tomcat apache org 8 http glassfish org this copy is P1 0 printing lt 189 PACKAGING FOR DEPLOYMENT lt 190 Although we ll leave it as an exercise for you to install and boot one of these servers we can give you an idea of how to deploy to them For Tomcat you ll simply copy a properly configured rou
283. r Download rake baseball Rakefile task default gt jar javadoc this copy is P1 0 printing Jar Rake will run the two subtasks one right after the other If each one takes six seconds you can t do any better than twelve seconds total But these two actions are independent there s no real reason to make Rake wait for one to finish before starting the next So let s create a new task called parallel that runs these two subtasks in separate threads In plain Ruby this wouldn t buy us much but JRuby uses Java s threads which are significantly more powerful All you have to do to mark a group of tasks as independent of one another is to define it with multitask in place of task Download rake baseball Rakefile multitask parallel gt jar javadoc If you run this example with rake parallel on a multicore machine you should see two of your cores doing work here Multiple Files As a passionate developer you no doubt care about modularity in your software and want to apply the same principle to your build scripts as well Breaking a complicated Rakefile into a group of related files makes a lot of sense But how do you tie them all together Since Rake is just Ruby you could use Ruby s built in require mecha nism to load a file full of subtasks into your main Rakefile You could also use Rake s alternative which is called import and has slightly dif ferent semantics But the simplest
284. r Installation 2 http github com brynary webrat 3 If Webrat isn t aware of your particular web framework you can go back to running your own server and use the simple Webrat API on top of Selenium or other back ends Report this copy is P1 0 printing Jan ACCEPTANCE TESTING Introduction to Rails on page 98 From the rouge directory you created in that chapter make a subdirectory called features and a file called features manage_restaurants feature with the following text Download introduction_to_rails rouge features manage_restaurants feature Feature Manage restaurants In order to provide up to the minute listings As a guidebook author I want to add remove and modify restaurants Background Given I am logged in as an admin Scenario Add a restaurant Given the following restaurants name Kenny and Zuke s Horse Brass Pub When I add the following restaurant name New Old Lompoc Then I should see the following restaurants name Kenny and Zuke s Horse Brass Pub New Old Lompoc This format should feel familiar from the previous Cucumber examples We ve added a couple of new twists though The Background section adds a step that will run at the beginning of each Scenario It doesn t really save you any typing if you have only one test case But it spares the linguistic awkwardness of Given am logged in And the following restaurants Also note that you can define tables of test code
285. r Java project already includes other scripting languages you probably don t want to use a separate API for each language JRuby supports the two most popular Java embedding APIs Bean Scripting Framework the older of the two began at IBM and is now Report erratum THE NITTY GRITTY hosted by the Apache Jakarta project javax scripting also known as JSR 223 is part of the official JDK Both have a similar flavor you connect a general purpose script manager to a language specific scripting engine In case you re curious here s how the final Historian example from earlier would look in JSR 223 minus the exception code First the imports at the top need to change a little Download ruby_from_java historian src book embed Historian8 java package book embed import java lang NoSuchMethodException import java util List import javax script Invocable import javax script ScriptEngine import javax script ScriptEngineManager import javax script ScriptException Now for the Ruby embedding code Download ruby_from_java historian src book embed Historian8 java public static void main String args throws ScriptException NoSuchMethodException ScriptEngineManager manager new ScriptEngineManager ScriptEngine engine manager getEngineByName jruby Invocable invocable Invocable engine engine eval LOAD_PATH lt lt lib engine eval require archive8 Object archive engine eval Archi
286. r the develop ment database which is the one you ll use during most of this chapter Download introduction_to_rails rouge config database yml development adapter sqlite3 database db development sqlite3 pool 5 timeout 5000 If you were developing the application with a database server such as MySQL or PostgreSQL you d edit this file to change the connec tion information Since we ll be using the embedded SQLite database there s no need to change anything here for now Before you start the application we should point out there is another step you d need to perform had we started with MySQL creating the databases Rails provides a handy command that will create a separate database for each environment As with many maintenance tasks you run it using Rake the Ruby build and maintenance tool This step is unnecessary with SQLite which will create the files for us the first time our Rails app hits the database If you re really curious you can safely run the command anyway Download introduction_to_rails output rake db create txt jruby S rake db create all Cin code introduction_to_rails rouge 7 Your automated tests will use the test database instead It s important to keep this one separate since Rails destroys and re creates it every time you run the tests 8 We ll cover Rake in more detail in Chapter 7 Building Software for Deployment on page 165 BUILDING OUR MODELS 111 5 3 The R
287. r things that your user will see and Symbols for things that the rest of your Ruby program will see class names method names database columns and so on Regular Expressions Another part of Ruby s Perl heritage is its extremely good support for regular expressions These allow you to succinctly describe the struc ture of a piece of text and then see whether some string has that struc ture You create a Regexp by enclosing your pattern in slashes pattern A C A Z 2 d 5 if Portland OR 97201 pattern puts Yay it matches puts City 1 puts State 2 puts ZIP 3 end A CLOSER LOOK lt 283 Regular expression syntax is a language all its own The previous exam ple shows a few common operations You use square braces to match a single character of a certain kind plus signs or braces to denote repeti tion and parentheses to say Store this partial match in a variable for later Booleans In Ruby booleans are just like any other values They have a class you can call methods on them and you can even add your own methods to them In Ruby true is the sole instance of a class called TrueClass and false is the only instance of FalseClass The equivalent of Java s null is called nil and it is the only instance of NilClass One important thing to note is that Ruby considers nearly any value true enough to satisfy conditional expressions like if Only false and nil
288. rable uniquely named documents resources Client code which may or may not be a browser can read and modify resources by using the HTTP protocol s four simple verbs POST GET PUT and DELETE For example suppose you re creating a photo editing site With a traditional approach you might send a GET request to http example com show php to display an image or send POST requests to new php edit ohp or delete ohp to upload modify or remove an image With REST you d present each photo as a resource with a unique ID such as _hitp example com photos 12345 All operations viewing modifying and so on would take place through GET POST PUT and DELETE requests to that same address Think of it as convention over configuration applied to your API design x This is not the same thing as the four CRUD create read update destroy operations performed by many web apps see http jcalcote wordpress com 2008 10 16 put or post the rest of the story to use JRuby on any project speed stability infrastructure and so on The slightly longer answer is that Rails in its current incarnation is very good at many things but not absolutely everything JRuby can smooth over some of the remaining rough spots Deployment is proba bly the most interesting of these Deploying a Rails application is fairly well documented but getting everything right can still be difficult With JRuby you can package your Rails appl
289. race option 166 using with Warbler 196 198 Rakefile ro 166 Rawr 250 RedCloth 242 regular expressions 282 relational databases 133 164 remote administration 319 321 REPL read eval print loop 24 REST Representational State Transfer 103 104 Ribs 154 161 RSpec integration with Maven 182 RUBEUS TEST DOUBLES RSpec Mocks 213 216 unit testing framework 202 205 Rubeus 36 246 250 Ruby driving Java annotated classes 53 54 93 calling Java functions 30 catching Java exceptions 50 extending Ruby programs 36 38 implementing Java interfaces 54 55 67 92 loading Java classes 41 42 method selection 290 291 monkeypatches 58 name mapping 41 44 overloaded Java methods 50 53 return values 292f 292 setting classpath 38 40 testing Java code 200 202 229 239 troubleshooting 55 58 type conversions 46 50 291 292f using Java objects 29 44 45 wrapping Java libraries 34 35 Ruby from Java calling compiled Ruby 87 91 catching Ruby exceptions 69 compile mode options 74 embedding strategies 74 76 passing strings 64 ScriptingContainer objects 62 66 72 74 supported embedding frameworks 70 thread support 72 73 wrapping Ruby libraries 62 63 Ruby language assignment operator 284 blocks 287 288 booleans 283 class definitions 275 278 class methods 278 279 class modifications 279 collections 285 control structures 286 data types 281 283 displaying information 289 dynamic typing 272 27
290. rate ALL src bookie The word ALL in the final command indicates that Monkeybars should generate a model view and controller Report erratum 1 0 printing January 2011 MONKEYBARS lt 251 If you look at the new top level bookie directory you ll find a structure that may remind you of a Ruby on Rails application Since all Mon keybars applications share this layout learning the conventions once means you ll know your way around any new project Here are the more important files and directories e lib java Location of jar files for JRuby and Monkeybars e lib ruby External Ruby libraries such as RedCloth e src application_controller ro and src application_view ro Code shared across all user defined controllers and views e src manifest ro Where you ll specify external dependencies e src bookie Your custom model view and controller Once you have the project structure in place it s time to hook it up to NetBeans Launch the IDE and then select New Project from the File menu In the dialog box that appears choose Java in the left pane and Java Project with Existing Sources in the right pane Hit Next and browse to the bookie directory Type Bookie for the project name Hit Next again Add the src subdirectory to the list of project source directories When you click Finish you should see the Bookie project in the list on the left side of the screen Right click the project icon and choose Prop erties Click
291. re s a simple example of a JUnit 4 test which uses annotations to indicate which methods are tests Download compiler waveform test_waveform rb require java require waveform_with_sigs java_import org junit Test class TestWaveform java_annotation Test java_signature void testRms def test_rms de 10 rms Waveform new dc rms org junit Assert assert_equals rms 1 0 0 001 end end Like most of the other java_ directives the annotation line must be specified as a string so it can be inserted into the generated Java out put This technique isn t just for spelling out test cases It s fully compatible with more complex uses like the Jersey framework With Jersey you can serve requests with a simple Java object thanks to a few annota tions that tell the server the URL that goes with each method Deploying Compiled Code We ve talked about compiling Ruby code to make it more pleasant to run faster execution integration with frameworks and so on Now let s talk about compiling Ruby to make it easier to deploy 3 http blog headius com 2010 06 restful services in ruby using jruby Atm rratum this copy is P1 0 printing Ja THE DETAILS Compiling Several Files at Once For larger projects you will likely have a carefully arranged directory of Ruby source code with each component in its own folder What s the easiest way to compile an application with this kind of setup It w
292. re it started out as the project RBehave which in turn owes its heritage to JBe have Both of these were created by Dan North a coder at ThoughtWorks and one of the fathers of BDD JBehave and the projects it inspired did much to define and spread the BDD way of developing software to the world All three steps are listed as undefined because we haven t yet told Cucumber how to visit the home page search for a term or look at the page title We ll eventually fill in that behavior The end of the test report gives us a starting point three Ruby snippets we can paste into a text editor Given AI am on the search home page do pending express the regexp above with the code you wish you had end When AI search for C A do arg1 pending express the regexp above with the code you wish you had end Then Athe page title should begin with C A do arg1 pending express the regexp above with the code you wish you had end What goes inside those three blocks If you re using Cucumber for inte gration testing the job might be as simple as creating a couple of Ruby objects gluing them together and seeing how they interact You had probably lean fairly heavily on mocks to stand in for other parts of the system On the other hand functional and acceptance tests typically drive the full app instead of just a few pieces The method by which you do that is highly context dependent Some applications hav
293. re meant to be used not just Software Development read Agile Cards for Agile Teams Agile in a Flash Speed Learning Agile Software Sao I Development Z Jeff Langr and Tim Ottinger 110 pages ISBN 978 1 93435 671 5 15 00 http pragprog com titles olag Jeff Langr and se The Agile Samurai Faced with a software project of epic proportions Tired of over committing and under delivering Enter the dojo of the agile samurai where agile expert Jonathan Rasmusson shows you how to kick start execute and deliver your agile projects n You ll see how agile software delivery really works The Agile Samurai and how to help your team get agile fast while pe ones having fun along the way Great Sotware 5A sA The Agile Samurai How Agile Masters Deliver Great Software Jonathan Rasmusson 275 pages ISBN 9781934356586 34 95 http pragprog com titles jtrap Jonathan Rasmusson Stet by Susannah Davidson Pfaizer The Pickaxe book named for the tool on the cover is the definitive reference to this highly regarded language e Up to date and expanded for Ruby version 1 9 e Complete documentation of all the built in classes modules and methods Complete descriptions of all standard libraries Learn more about Ruby s web tools unit testing and programming philosophy b The Pragmatic Programmers Guide Raby a Programming Ruby 1 9 The Pragmatic Programmers Guide Dave
294. rea E Deets Mediterraneo will never leave you disappointed gt i functional DESC m a restaurant address 1244 Kings Cross Road London WC1X 8cc gt aparma restaurant phone 44 1432 3434 v unit A gt E helpers z E restaurant save 2 ActiveRecord Base save ActiveRecord Base Ls iministratne test O save_with_transactions perform_validatio ActiveRecord Transactions a bd Found TORON O save_with_transactions ActiveRecord Transactions S e save_with_validation perform_validation ActiveRecord Validations elo ca 782 38 a save_with_validation ActiveRecord Validations 2 a Choosing item with will overwrite the rest of identifier after caret 5 N i P 1B 9 Changes E1 0 Messages C96 TODO 26 20 Insert MacRoman B BiMofi27 Figure 1 1 The RubyMine IDE EI As you can see in Figure 1 1 there s a lot to RubyMine We ll just men tion a couple of points that are hard to show in a screenshot For one thing the tool is aware of popular test and directory naming conven tions for Ruby projects so you can jump automatically between a piece of code and its tests It also supports several refactoring techniques on Ruby code NetBeans NetBeans is an open source development environment with support for several different programming languages 3 You can download a Ruby specific build
295. reason JRuby provides a couple of shortcuts The sim plest is java_alias which lets you choose a new name for the Java over load Download java_from_ruby how_many_bits rb class HowManyBits java_alias needed_for_int neededFor Java int end puts bits needed_for_int 1_000_000 The other alternative is to use java_method to get a reference to an overload You can pass this reference around your program and call it at any time Download java_from_ruby how_many_bits rb bits_needed_for bits java_method neededFor Java int bits_needed_for call 1_000_000 gt 32 CALLING OVERLOADED METHODS Not only will java_alias and java_method clean up your code they ll also make it a little faster since JRuby won t have to keep looking up the same Java overload Annotated Classes Some Java methods expect the objects handed to them to have specific annotations Assume we ve defined a custom PerformedBy annotation containing the name of someone who performs a feat of skill Download java_from_ruby Sorcery java PerformedBy name Charlie public class Sorcery Nothing up my sleeve If we wanted to describe the feat of skill at runtime we could do so by reading the annotation Download java_from_ruby Chronicler java import java lang annotation Annotation public class Chronicler public static void describe Class lt gt c PerformedBy p PerformedBy c getAnnotation PerformedBy class
296. require test spec require java java_import java util HashMap describe an empty HashMap do 3 There s actually a slight difference of syntax RSpec expectations favor spaces and underscores while test unit uses dots everywhere this copy is P1 0 printing RUBY TEST FRAMEWORKS lt 206 before each do map HashMap new end it should be empty do map isEmpty should be true end it with an added entry should not be empty do map putC hello world G map isEmpty should not be true end it should associate a value with a key do map putC hello world map get hello should equal world end it should raise error on entryset iterator next do proc do G map entrySet iterator next end should raise NativeException end end and running would look the same as in Test Unit jruby hashmap_test_spec rb Loaded suite hashmap_test_spec Started Finished in 0 02 seconds 4 tests 4 assertions 0 failures 0 errors There is nothing really revolutionary here but that s kind of the point Readability is noticeably better than in Test Unit particularly when we have a failure Let s see what happens if we force one of the tests in hashmap_test_spec rb to fail jruby hashmap_test_spec rb Loaded suite hashmap_test_spec Started yal x Finished in 0 117 seconds 1 Failure test_spec an empty HashMap 003 should associate a value with a key an empty hashmap_test_spec
297. revisions git Git open git diffCrevisions start revisions finish to_a end end So far we ve been calling the history method by building up a string in Java with the word history in it But JRuby can actually call the method directly using the callMethod operation callMethod takes the Ruby object whose method we re calling the receiver the method name and whatever parameters you re passing in Download ruby_from_java historian src book embed Historian java ScriptingContainer container new ScriptingContainer container setLoadPaths Arrays asList lib container runScriptlet C require archive6 Object archive container runScriptletC Archive new List lt GitDiff gt files List lt GitDiff gt container callMethod archive history new Revisions args 0 args 1 this copy is P1 0 printing A REAL LIFE EXAMPLE SOURCE CONTROL for GitDiff file files System out printiInC FILE file getPathQ System out printiIn file getPatch This is more like it We re passing a parameterized list straight into a Ruby method There s just one more thing we need to do before we call it a day So far we have been running our program with valid Git revision iden tifiers like HEAD 2 What happens when we give it an invalid revision bin historian6 PASTA NOODLES ruby_from_java historian lib git lib rb 700 in command git diff p PASTA NOODLES 2 gt amp 1 fata
298. ridden the default here i extension Using the i flag you can process a large number of files at once in place Like the n flag it wraps a loop around your program But instead of passing in input from the user it passes in the contents of external files The filenames are passed on the command line after the flag After each pass through the loop JRuby overwrites the contents of the external file with your program s output That s why this flag takes an extra parameter it s a file extension so that JRuby can back up the input files Here s what in place processing looks like in action echo matz gt tmp test cat tmp test matz jruby p i bak e _ upcase tmp test cat tmp test MATZ cat tmp test bak matz Here we ve combined the i flag with p so that for each file the con tents of the _ variable will get written back out to the original file l You ll notice in the 0 example we saw earlier the strings we processed still had their record terminators attached the q and n characters If you want to clean that up without explicitly calling String chop on each line pass I to JRuby This flag calls chop on each line for you which removes record separators in the sense of the 0 flag from the end of a string Here s an earlier example modified to use 4 echo fooqbarqbaz jruby 1 0161 e 3 times p gets bar baz Report erratum PROPERTIES lt d
299. rk in a loop A complicated method might get called frequently but have many cold paths through the code An extremely long method can exceed limits set by JRuby or the JVM itself In all these situations a method will remain interpreted forever Both JRuby s JIT compiler and the principles of good software design favor breaking large algorithms into smaller methods Moving On to AOT As we ve seen JRuby usually runs in full auto mode You don t have to decide when to interpret or compile a particular section of your code There are however times when you want to invoke JRuby s ahead of time compiler yourself and generate bytecode Just as Java program mers are used to typing javac SomeJavaProgram java to generate Some JavaProgram class you can type jrubyc some_ruby_program rb to generate some_ruby_program class Why would you want to do this There are a few different situations where this technique comes in handy e Youre deploying to a system that requires your code to be in class files e You don t want your original Ruby source code to appear in your finished program e You re writing a plug in for a tool that isn t sophisticated enough to call the Ruby Embed API e You re looking at one of those rare cases when AOT compilation really is faster such as the Android platform It s not difficult to take an existing Ruby library compile it and call it from Java In fact it s only a short step beyond
300. rld Webrat Methods World Rack Test Methods Once that s done you can run an all in one Rake task that takes care of setting up the database and running the test jruby S rake cucumber Because this test doesn t require a browser or server it s easy to run on a variety of machines from your development team s PCs to the contin uous integration server But Webrat doesn t try to be a full browser and you may have some tests that require one Many projects successfully use a mix of both styles this copy is P1 0 printing Jan PLUGGING INTO JAVA 229 9 3 Plugging Into Java By this point we ve seen several compelling Ruby test frameworks Some of them are only of tangential interest to Java users but oth ers can provide inspiration for real Java projects In this section we ll talk about which ones are good candidates for your Java project We ll finish up with a discussion of how JRuby and the existing Java test frameworks play together JtestR JtestR is a new framework that simplifies using Ruby for testing Java projects It doesn t include much original code instead it collects sev eral state of the art Ruby libraries together with some glue code geared toward Java testing Why use Ruby to test Java Because the ease of writing tests in Ruby will encourage you to write more and better tests With JtestR you don t have to hook up any of the plumbing that would normally be necessary to integrate
301. rname string password string jruby script rails g model Reviewer name string description string username string password string jruby script rails g model Review restaurant_id integer reviewer_id integer title string content text jruby script rails g model Comment said_by string content text commentable_id integer commentable_type string this copy is P1 0 printing Ja BUILDING OUR MODELS lt 4 116 Note that the Comment model doesn t have a restaurant_id or a review_id column Instead it has a commentable_id and a commentable_type Rails will use these fields to track whether a particular comment was made about a restaurant or about a review We ll see how in a moment first though we need to migrate the database Download introduction_to_rails output rake db migrate 2 txt jruby S rake db migrate Cin code introduction_to_rails rouge CreateAdministrators migrating s s S create_table administrators gt 0 0060s gt 0 rows CreateAdministrators migrated 0 00805 s s s CreateReviewers migrating s s s s SS S S s s SS create_table reviewers gt 0 0050s gt 1 rows CreateReviewers migrated 0 0060s s s s S CreateReviews migrating s s s s s ssSSs ssSSSS sSSSS 5 5 create_table
302. rry The syntax is exactly like what you d use for any other function Explicit Coercion Though JRuby s mapping between Ruby and Java types will cover most of the cases you ll encounter you may occasionally want to coerce Ruby types explicitly to specific Java ones For instance if JRuby s auto matic conversion is likely to be time consuming you might want to pre convert the object Download java_from_ruby string_demo rb ruby_string This is a large string we don t want to convert frequently java_string ruby_string to_java StringDemo method_taking_a java_string When you require java every Ruby object gains a to_java method Either you can call it with no parameters to get the nearest Java type or you can specify a particular Java class you want to convert to The Extra Mile The Ruby Java conversions we ve seen so far have been like the sim ple translations in a tourist s phrasebook They re fine for rudimentary communication But as a seasoned traveler you enjoy speaking in a more fluent idiomatic way JRuby includes tons of extra conveniences for using Ruby idioms with Java classes and vice versa Here are a few of the most common ones Strings and Regular Expressions Ruby s to_s and Java s toString are a natural fit for each other Define to_s on your Ruby object pass it into Java and any Java code expecting to find toString in your class will be able to call it Java regular express
303. rt routines so jruby jar needs to be on your CLASSPATH Also the compiler compiles only the files you specifically pass to it If you refer ence some_ruby_library rb you ll have to compile that extra rb file yourself or ship it in source form alongside your class file When you look at compilation in detail there are a lot more shades of distinction between no compilation at all and compile everything up front JRuby may compile parts of your program to Java bytecode at runtime to improve performance You ll find a detailed discussion of this and other aspects of compilation in Chapter 4 The JRuby Compiler on page 78 14 There s more on how JRuby uses the Java classpath in Chapter 2 Driving Java from Ruby on page 31 Report erratum 1 7 JAVA INTEGRATION Java Integration JRuby can use Java objects much as if they were Ruby objects Here s a simple example that exercises Java s ArrayList class Download introduction interop rb require java list java util ArrayList new list lt lt List of list lt lt 3 list lt lt assorted_items list each do item puts fitem class item end As you can see we can add a variety of objects including native Ruby types like Symbols to the list JRuby even provides appropriate Ruby iteration idioms for Java collections which is why we can call each on the list in this example Of course Ruby has its own perfectly respectable co
304. ry we need to use the Windows stdcall calling convention Next we specify the two functions we need based on their signatures Notice that we can do simple type definitions so that the function decla ration will use the window handle type familiar to Windows developers We ve deliberately chosen an API call that takes a buffer so that we can talk about how to share strings with the C world The call to Memory Pointer new allocates a buffer that stays in memory just for the lifetime of the attached block Since this is just a generic pointer to raw storage Report this copy is P1 0 printing Janua FOREIGN FUNCTION INTERFACE lt 312 we have to tell FFI to interpret the result as a string using the get_string call If you save the program as windows ro and run it you should see something like this C gt jruby windows rb jruby Cmd Ready for something a little more intricate Let s move on to our second example A Mac Example and More This program will get into a couple of FFTs more advanced features callbacks and data structures We re going to use the UNIX signal handling system to set a timer and then wait for it to fire As before we are going to call two C functions Here are their C declarations Download ffi defs c unsigned int alarm unsigned int int sigaction Cint struct siginfo struct siginfo FFI takes great pains to represent these functions legibly in Ruby Download ff
305. s Successfully installed bundler 1 0 2 Successfully installed activesupport 3 0 1 Successfully installed builder 2 1 2 Successfully installed i18n 0 4 1 Successfully installed activemodel 3 0 1 Successfully installed rack 1 2 1 Successfully installed rack test 0 5 6 Successfully installed rack mount 0 6 13 Successfully installed tzinfo 0 3 23 Successfully installed abstract 1 0 0 Successfully installed erubis 2 6 6 Successfully installed actionpack 3 0 1 Successfully installed arel 1 0 1 Successfully installed activerecord 3 0 1 Successfully installed activeresource 3 0 1 5 See Agile Web Development with Rails RTHO8 GOING ROUGE lt 4 106 Successfully installed mime types 1 16 Successfully installed polyglot 0 3 1 Successfully installed treetop 1 4 8 Successfully installed mail 2 2 7 Successfully installed actionmailer 3 0 1 Successfully installed rake 0 8 7 Successfully installed thor 0 14 3 Successfully installed railties 3 0 1 Successfully installed rails 3 0 1 24 gems installed Our restaurant guide will make it easy for someone who s considering a restaurant to find reviews for it They ll want to search restaurants read reviews and comment on either a review or a restaurant Visitors will be generating most of this content but we ll also need an administrator account for creating restaurants You ll see later how to offer these two different views of the same data Deciding on Our Models From the previous s
306. s a strong parallel between the Ruby and Java ways of passing extra search paths on the command line Ruby uses the I switch ruby I path to library my_program rb Report erratum DEALING WITH THE CLASSPATH N fed Charlie Says 5 The Default Package Notice here we re using the Java prefix In this case it s because our Java based Ackermann class is in the default package Such classes can be accessed immediately under the Java namespace EN JRuby supports I for Ruby code naturally but also understands Java s cp classpath option for Java classes jruby J cp path to library jar C gt jruby J cp C path to library jar Remember that J specifies that JRuby should pass the cp option to the underlying Java runtime With an Environment Variable As we did with the command line arguments we re going to draw a parallel between the ways Ruby and Java use environment variables If you re a lazy typist like we are you re probably used to storing your most commonly used Ruby search paths in the RUBYOPT environment variable export RUBYOPT I path to common 1 ibraries C gt set RUBYOPT IC path to common ibraries JRuby supports RUBYOPT for finding Ruby code and the Java equivalent CLASSPATH for finding Java classes export CLASSPATH CLASSPATH path to 1ibrary jar C gt set CLASSPATH CLASSPAT
307. s and straightforward code Before we get into those specific uses we d like to take you on a tour of the best of JRuby in this chapter We ll start by showing you a couple of easy ways to get JRuby onto your system including a hassle free no installation option and what to do with it once you have it 1 http rails primer appspot com 2 http ruboto org 3 http www infog com presentations martin jruby limelight INSTALLING JRUBY When you have JRuby running you ll see firsthand how JRuby is a top notch Ruby environment You ll try out code interactively in a live interpreter which is a great way to learn the language and its libraries You ll write a stand alone script just like the ones you use for everyday system automation tasks We ll also show you how JRuby does a few things other Rubies can t do You ll compile a Ruby program to a Java class file You ll call seamlessly into Java libraries just as easily as calling Ruby code Ready to begin your journey 1 1 Installing JRuby JRuby is built for easy deployment After all it needs to fit in envi ronments ranging from your development laptop to a tightly controlled production server Accordingly there are a lot of ways to get it onto your system We ll look at a couple of the more common ones here Using an Installer The easiest way to install JRuby is to use one of the prebuilt installers available from the official download site These will take care of
308. s are private there s usually no need to get at them from outside the class let alone outside the language Still there may be times when you really need this capability If you have the following Java class Download java_from_ruby FieldDemo java public class FieldDemo private int somePrivateField 0 public FieldDemo you can reopen that is modify the class in JRuby and specify a Java to Ruby mapping for the field Download java_from_ruby field_demo rb class FieldDemo field_accessor somePrivateField gt some_field end obj FieldDemo new obj some_field 1 obj some_field gt 1 This will always work for public fields of a particular Java type and if your JVM s security settings are lenient enough most default configu rations are it will work for protected package visible and private fields as well Passing Parameters Even the simple method calls in the past few sections are the result of careful choreography on JRuby s part As we saw with the URL construc tors JRuby seems to know which among several overloaded versions of a Java method is the best fit for the way you re calling it in Ruby What about method parameters Unless it was written specifically for JRuby a Java method will not expect to be passed a bunch of Ruby objects So JRuby will automatically convert certain parameters from the original Ruby types to the Java types needed by the method Report err
309. s become available Join the Community http pragprog com community Read our weblogs join our online discussions participate in our mailing list interact with our wiki and benefit from the experience of other Pragmatic Programmers New and Noteworthy http pragprog com news Check out the latest pragmatic developments new titles and other offerings If you liked this eBook perhaps you d like to have a paper copy of the book It s available for purchase at our store pragprog com titles jruby Contact Us Online Orders www pragprog com catalog Customer Service support pragprog com Non English Versions translations pragprog com Pragmatic Teaching academic pragprog com Author Proposals proposals pragprog com Contact us 1 800 699 PROG 1 919 847 3884
310. s logic in your Ruby domain models can be kept separate from the GUI 10 5 Limelight And now for something completely different Up to this point we ve considered frameworks of varying levels of abstraction But even the most helpful frameworks still expose us to some of Swing s gory details Limelight is a radical departure from the other frameworks Although it uses a few Swing classes for things like menus most of the drawing is done directly onto a canvas object The result is that Limelight has only a minimal connection to Swing Limelight uses a theater metaphor for the various parts of your pro gram Here are its main concepts Production Your application Stage A top level window what Swing would call a frame Report erratum 0 printing Jar LIMELIGHT lt 261 Theater A collection of stages Prop Any visible component of the UI Player A prop that also has behavior Scene A collection of props that can be loaded into a stage Cute huh Even if you re not normally a fan of these kinds of extended metaphors we d like you to suspend your disbelief hey another theater expression for a few pages Consider how these concepts might apply to a program Imagine you re writing a hardware configuration wizard You d use one theater with a single stage because wizards are typically single window programs Each time the user advances through a step you d cycle to the next scene which would have i
311. s lt outputDirectory gt lt sourceDirectory gt src lt sourceDirectory gt lt plugins gt lt plugin gt lt groupId gt org jtestr lt groupId gt lt artifactId gt jtestr lt artifactId gt lt version gt 0 6 lt version gt lt configuration gt lt port gt 20333 lt port gt lt configuration gt lt executions gt lt execution gt lt goals gt lt goal gt test lt goal gt lt goals gt lt execution gt lt executions gt lt plugin gt lt plugins gt lt build gt lt project gt To use the background server with this configuration file execute the jtestr server goal JtestR can be made to work with IDEs as well For an example of Eclipse integration see http www evalcode com 2008 08 jruby jtestr in eclipse Reusing Java Tests With JtestR you can take your existing Java tests written for the JUnit or TestNG framework and run them right alongside your new Ruby this copy is P1 0 printing Ja PLUGGING INTO JAVA 232 tests All you have to do is add the names of your Java test classes to JtestR s config file which is called jtestr_config ro by default Download beyond_unit_tests jtestr jtestr_config rb junit com example SomeTest com example SomeOtherTest You can also go the other direction and let JUnit drive your Ruby tests as we ll see in a moment JtestR includes many smaller but still useful features For instance as we discussed in Section 8 3 Mocha on page 2
312. s stated goal is to manage an application s dependencies through its entire life across many machines systematically and repeat ably In more pragmatic terms it helps prevent conflicting or missing gems Although you can use Bundler with any Ruby application the integration story is particularly good with Rails 3 As we hinted in the previous section one of the files the rails new com mand creates is called Gemfile Let s take a look inside Download introduction_to_rails output Gemfile source http rubygems org gem rails 3 0 1 Bundle edge Rails instead gem rails git gt git github com rails rails git if defined JRUBY_VERSION gem activerecord jdbc adapter gem jdbc sqlite3 require gt false else gem sqlite3 ruby require gt sqlite3 end 6 http gembundler com GOING ROUGE lt 4 109 The Gemfile is just a place to declare the gems and libraries your appli cation needs Bundler shines when it s time to configure those depen dencies at install time and runtime To make Bundler install the depen dencies run the bundle install command Download introduction_to_rails output bundle install ixt jruby S bundle install Fetching source index for http rubygems org Using rake 0 8 7 Using abstract 1 0 0 Using activesupport 3 0 1 Using builder 2 1 2 Using 118n 0 4 1 Using activemodel 3 0 1 Using erubis 2 6 6 Using rack 1 2 1 Using rac
313. se designations appear in this book and The Pragmatic Programmers LLC was aware of a trademark claim the designations have been printed in initial capital letters or in all capitals The Pragmatic Starter Kit The Pragmatic Programmer Pragmatic Programming Pragmatic Bookshelf and the linking g device are trademarks of The Pragmatic Programmers LLC Every precaution was taken in the preparation of this book However the publisher assumes no responsibility for errors or omissions or for damages that may result from the use of information including program listings contained herein Our Pragmatic courses workshops and other products can help you and your team create better software and have more fun For more information as well as the latest Pragmatic titles please visit us at http www pragprog com The team that produced this book includes Editor Jacquelyn Carter Indexing Potomac Indexing LLC Copy edit Kim Wimpsett Production Janet Furlow Customer support Ellie Callahan International Juliet Benda Copyright 2011 The Pragmatic Programmers LLC All rights reserved No part of this publication may be reproduced stored in a retrieval system or transmit ted in any form or by any means electronic mechanical photocopying recording or otherwise without the prior consent of the publisher Printed in the United States of America ISBN 10 1 934356 65 4 ISBN 13 978 1 934356 65 4 Printed on acid free paper P
314. sider the other side of the coin embedding Ruby code in a Java project There are several situations where this capability comes in handy Here are a few examples A Java program might need to perform some task for which there is no Java library or for which the Ruby libraries are easier to use than their Java counterparts For example Ruby s image_voodoo library exposes a simpler API than the native Java2D framework Users might want to extend your Java game or animation program with their own scripts With JRuby you can use Ruby as your project s extension language You might be deploying a Ruby program into an otherwise Java heavy environment where your team wants to test your Ruby code using their JUnit or TestNG harness If you re wrestling with an existing Java code base you might want to get the benefits of Ruby s flexibility by rewriting parts of your program in Ruby All these uses look the same from the Java side so we re going to con centrate on the first case using a Ruby library from a Java program 1 http rubyforge org projects jruby extras A REAL LIFE EXAMPLE SOURCE CONTROL 3 1 A Real Life Example Source Control Over the next several pages we re going to build a Java app that calls into Ruby with increasing sophistication We ll start with a simple Hello world like program and end up performing a useful task What useful task Glad you asked We re going to build a source c
315. so obvious Slowdowns are revealed only by careful profiling Here s how we might have profiled the Ackerizer program jruby sample J Xss128m ackerizer rb Here are the relevant lines of the output trimmed a bit to fit on the page 29 6 org jruby RubyFixnum i_method_1_O RUBYINVOKER op_equal call 24 5 org jruby internal runtime methods Cal1Configuration 3 pre 14 0 org jruby internal runtime methods JittedMethod call 11 1 org jruby RubyFixnum i_method_1_O RUBYINVOKER op_minus call 5 8 org jruby RubyFixnum i_method_1_O RUBYINVOKER op_plus call 5 0 ruby jit ruby Users username ackermann ack3178554_ 3306611 file _ 4 2 org jruby runtime callsite CachingCal1Site call 4 1 ruby jit ruby Users username ackermann ack3178554_ 3306611 file __ The program spends 98 3 percent of its calculation time either in ack itself or in the basic math operations that underlie it It s a small wonder that fixing this one function made the program so much more respon sive J Sometimes you need fine grained control over the performance of the Java runtime The java command has its own set of parameters for this purpose and you can use any of them from JRuby Just prepend J to the Java option you want with no spaces For example you may want to specify how much memory to allocate to the JVM In Java you d pass the Xmx option to the runtime like this java Xmx512m com example someJavaProgram COMMAND LINE OPTIONS lt d 3
316. sq property to display all the generated SQL code We re also marking the database explicitly as the default The default database is the one Ribs will use for data operations that don t name a specific database There s an easier way to set the default which we ll see in a moment The next few examples are all designed to build on one another You ll create a Ruby file with just the connection information and gradually add code to it The program should work with little modification on just about any database system Setting up most commercial servers with Hibernate is not for the faint of heart it involves finding installing and configuring both JDBC drivers and Hibernate dialect classes Instead we re going to base our example on the lightweight Apache Derby database which is much easier to install 3 Just download a recent build and copy derby jar into your project directory 13 http db apache org derby Report erratum is P1 0 printing January 2011 As we did with the MySQL example a moment ago we need to start by connecting to the Derby database Download databases ribs_use rb require rubygems require ribs Ribs DB define do db db dialect Derby db uri jdbc derby using_jruby create true db driver org apache derby jdbc EmbeddedDriver end Let s do a quick check to make sure Hibernate and Derby can find each other The following code should produce empty output with no err
317. ssfully run an empty test let s actually exercise the Restaurant model First we ll check that we can create a restau rant all of these tests should be added inside the RestaurantTest class in test unit restaurant_test rb Download introduction_to_rails rouge test unit restaurant_test rb def test_can_create_restaurant_with_only_name Restaurant create name gt Mediterraneo end There are several ways to create new instances with ActiveRecord In this case we ll use the create method which will save a new object to the database immediately The exclamation mark signifies that the method will raise an exception if something goes wrong By contrast the nonpunctuated create method will ignore errors In test cases it s usually easier to let ActiveRecord raise an exception so that the test harness can record it as a failure In the next test we ll make some changes to a restaurant and save it to the database Download introduction_to_rails rouge test unit restaurant_test rb def test_can_instantiate_and_save_a_restaurant restaurant Restaurant new restaurant name Mediterraneo restaurant description lt lt DESC One of the best Italian restaurants in the Kings Cross area Mediterraneo will never leave you disappointed DESC restaurant address 1244 Kings Cross Road London WC1X 8CC restaurant phone 44 1432 3434 restaurant save end this copy is P1 0 printing Jan or Shohei Tan BUILDING OUR MODEL
318. sting all kinds of pro grams because macros give your tests the same level of expressive power For example if somewhere in your Rails code you have an asso ciation like this has_many fubars you can test it like this using the Rails helpers that come with Shoulda should_have_many fubars Many of these features are present to some degree in other frameworks But where Shoulda really shines is in its simplicity We ve covered most of its core usage here All that s left are a few specific conveniences for Rails developers There s no hazing period on the learning curve and even the source code makes for good reading or Shohei Tan GOING TO THE NEXT LEVEL WITH ZENTEST lt 212 8 2 Going to the Next Level with ZenTest ZenTest is a collection of useful tools written by Ryan Davis and others for simplifying Ruby testing The ones most applicable to JRuby are unit_diff autotest and multiruby You can get them all in one fell swoop by installing the ZenTest gem note the capitalization jruby S gem install ZenTest unit_diff reformats test logs so you can eyeball a printout and see exactly what went wrong Java developers will recognize this feature from JUnit All you have to do is pipe your test output to the unit_diff com mand like this jruby test your_test_case rb jruby S unit_diff This will give you output similar to what you d normally see but with the error messages conveniently
319. t Warbler looks for a Rails app by checking for a Rails specific Rake task named environment 2 Next it looks for a Merb app by checking for a Merb specific task named merb_env Report erratum this copy is P1 0 printing Jan PACKAGING FOR DEPLOYMENT lt 192 3 Finally it looks for a generic Rack based application by checking for a Rack specific configuration file named config ru Note that this process sometimes loads the full application environ ment which may perform heavyweight actions such as connecting to the database If you don t want that to happen you can turn off autode tection see Section 7 4 Warbler Configuration on the following page Static Assets Warbler uses Rails convention of expecting static assets to be in the public directory It copies these assets to the root of the war file and strips the public prefix from all the filenames Ruby Gems Packaging gems is where it gets a little trickier since Ruby allows you to require a library without explicitly declaring it as a gem Warbler only knows of three explicit ways of declaring what gems your application uses e Rails 2 applications Warbler loads the Rails environment and looks at config gems as specified in the config environment ro file As long as you declare your gem dependencies here Warbler will be able to find them e Rails 3 applications and other projects that use the Bundler gem packaging system Warbler uses the list of
320. t aculo us You Never Knew 2007 9781934356012 448 JavaScript Could Do This Rails for NET Developers 2008 9781934356203 300 Rails for PHP Developers 2008 9781934356043 432 Rails Recipes 2006 9780977616602 350 Rapid GUI Development with QtRuby 2005 PDF Only 83 Release It Design and Deploy Production Ready 2007 9780978739218 368 Software Scripted GUI Testing with Ruby 2008 9781934356180 192 Seven Languages in Seven Weeks A Pragmatic 2010 9781934356593 300 Guide to Learning Programming Languages Ship It A Practical Guide to Successful Software 2005 9780974514048 224 Projects SQL Antipatterns Avoiding the Pitfalls of 2010 9781934356555 352 Database Programming Stripes and Java Web Development Is Fun 2008 9781934356210 375 Again Test Drive ASP NET MVC 2010 9781934356531 296 TextMate Power Editing for the Mac 2007 9780978739232 208 The Agile Samurai How Agile Masters Deliver 2010 9781934356586 280 Great Software The Definitive ANTLR Reference Building 2007 9780978739256 384 Domain Specific Languages Continued on next page Title Year ISBN Pages The Passionate Programmer Creating a 2009 9781934356340 232 Remarkable Career in Software Development The RSpec Book Behaviour Driven Development 2010 9781934356371 448 with RSpec Cucumber and Friends ThoughtWorks Anthology 2008 9781934356142 240 Ubuntu Kung Fu Tips Tricks Hints and Hacks 2008 9781934356227 400 Web Design for Developers A Programmer s 2009 9781934356135 3
321. t down to the one hook Bookie needs Download guis limelight bookie production rb module Production attr_reader chapter_contents def production_opening require redcloth chapter_contents title gt 1 text gt end end 7 See The Compleat Works Of Wilm Shkspr Abridged BLS94 8 http pragprog com titles jruby source_code Report erratum this copy is P1 0 printing Jar LIMELIGHT lt 263 Bookie AOO i i 1 Edit Preview 2 Growl 3 saw the best Macs of my generation distracted by notifiers cluttered hysterical faded Add Chapter Figure 10 4 Bookie in Limelight The production_opening hook runs at startup which gives us the chance to bring in the libraries we need and do some initialization Notice that we ve also added an attr_accessor to make the list of chapters visible from our players and props The second file to look at is stages ro Limelight has defined a default scene for us We need to make our bookie scene the default instead Download guis limelight bookie stages rb stage default do default_scene bookie title Bookie location 200 25 size 400 400 end this copy is P1 0 printin LIMELIGHT lt 264 Notice that this file uses a concise readable syntax to describe the stage You ll find nice touches like this throughout Limelight Scene and Props Now let s go through the various props and players in the bookie scene
322. t for this example we ll assume the dental plan is outstanding MONITORING APPLICATIONS lt 316 Here s how you might generate a monthly report on signatures Download jmx check_sigs usr bin env jruby Dir home each do d if grep Initrode d signature empty puts The signature in d isn t good for the company end end Just like any other UNIX shell script you can use the first line of code the shebang line to associate this program with JRuby You can then give yourself execute permission for this file and run it directly chmod u x check_sigs check_sigs The signature in home ian isn t good for the company On Windows there are a couple of extra setup steps but nothing too tricky Using Explorer rename the file to check_sigs ro and then asso ciate ro files with the jruby exe program Finally add rb to the end of your PATHEXT environment variable Now you can run check_sigs directly from the command line C gt set PATHEXT PATHEXT rb C gt check_sigs The signature in home ian isn t good for the company As you can see Ruby can loop through directories and call out to other programs easily These tasks are the bread and butter of day to day automation E 2 Monitoring Applications Java has evolved a number of APIs that are useful to admins who have to keep application servers running and healthy The best known of these is JMX the Java Management Extensions librar
323. t of Rails Don t Repeat Yourself DRY According to the DRY principle each piece of information should live in exactly one place If you re writing a payroll app where each Employee needs a name and a salary you shouldn t have to define those fields in the database and your Ruby class And indeed in Rails you don t property information resides only in the database Convention over Configuration Also known as sensible defaults when you do things the way Rails expects you to you won t need to configure much For exam ple Rails will automatically find the table for your Recipe class provided the table is named recipes in the database It will also implicitly assign URLs like http example com recipes to Ruby methods like RecipesController index This idea is closely related to the DRY principle After all the best way of not repeating yourself is to not say anything at all 1 http exportcontrol org library conferences 2657 9 __Tracker_7_System_Overview pdf 2 See The Pragmatic Programmer HTOO Report erratum WuatT Is RAILS lt 100 AA Ola Says Rails embodies the Model View Controller MVC software pattern understanding this pattern will help you learn Rails A frequent trap for application developers is letting business logic creep into user interface code MVC tries to avoid this problem by providing three different buckets for your code the model the view and the controller
324. t the top of the file Download guis limelight bookie bookie styles rb fill_parent width 100 height 100 We ll show just one more style example before moving on the rounded corners of the right tab button Download guis limelight bookie bookie styles rb right_tab top_right_rounded_corner_radius 4 top_right_border_width 1 bottom_right_rounded_corner_radius 4 bottom_right_border_width 1 left_border_width 0 right_border_width 1 top_border_width 1 bottom_border_width 1 LIMELIGHT You can see how the right side of the button has a rounded border on both corners while the left side has no border at all because that s where the left tab button is The code is straightforward but verbose Unlike the CSS syntax that inspired it Limelight requires you to put each style on its own line We encourage you to look through the rest of the styles file to see how the scene is laid out When you re ready to move on catch the debut of our scene s players in the next section Players Players are just props that happen to contain behavior There are in fact two different types of players built in and user defined The built in types are the usual suspects buttons text areas and so on The user defined ones are for things like tab controls where we ve had to write custom code to show and hide each tab Let s just look at a simple control for now the Add Chapter button The button s definition in pr
325. t to an integer Fortunately the ActiveRecord library automates much of this mapping for you In the simplest cases if you follow the naming conventions you won t have to write anything except the class name There s a lot more to ActiveRecord than what s in Fowler s original design pattern These extra features allow ActiveRecord to handle the most common database related tasks you re likely to encounter Broadly speaking the library can be divided into four parts e Migrations e Model descriptions e Validations e Model usage We ll describe and give examples each of these parts soon but first we need to talk about how JRuby and ActiveRecord work together Report erratum RUBY DATABASE FRAMEWORKS lt 136 JRuby has supported ActiveRecord for quite a long time A collection of gems gives you a choice among various JDBC drivers to use with ActiveRecord You can choose to use either a driver specific to your database or a general driver it doesn t make much difference either way To install the general gem run this command the exact version number may vary jruby S gem install activerecord jdbc adapter Successfully installed activerecord jdbc adapter 1 0 2 java 1 gem installed To use a database specific gem instead first do a search for available gems jruby S gem search r activerecord jdbc REMOTE GEMS ActiveRecord JDBC 0 5 activerecord jdbc adapter 1 0 2 java 0 9 2 activerecord jd
326. ta preconverted and pass that in instead Or you could move that time sensitive loop into your Java code We don t mean to scare you away from the direct approach Start out by passing a Java object into Ruby If this doesn t meet your performance goals then measure and rework Returning Data to Java Getting data back into Java land is a little more involved Java knows less about JRuby than JRuby knows about Java In general there are three options e Return a Ruby object that implements a Java interface e Return a Ruby object that extends a Java class concrete or abstract e Construct a Java object in Ruby and return it 11 Technically there s a fourth option calling become_java on a Ruby class But we don t recommend it Report erratum EMBEDDING STRATEGIES The first two options are similar in that you are returning a Ruby object that is tied to the JRuby runtime it came from If your Java code calls methods on the object these invocations will land back in the same JRuby runtime As we saw in Section 3 2 Containers and Contexts on page 72 this reuse of runtimes can have interesting consequences for multithreaded Java programs If you are passing objects between threads without using THREADSAFE mode you can crash the Ruby runtime The third option is much less prone to threading issues than the other two choices It can also be slightly faster since you re not dispatching function calls from
327. tably omits foreign key relationships and composite primary 3 Fora discussion see http lists rubyonrails org pipermail rails core 2006 February thread html 794 Report erratum lt 101 WHAT IS RAILS lt 102 keys Most of these can be added with the use of plug ins For more details on this component of Rails see Chapter 6 JRuby and Relational Databases on page 133 ActionPack ActionPack takes care of presenting your models to users and responding to the actions they perform It consists of three parts ActionView and ActionController correspond to the view and con troller parts of MVC while ActionDispatch is responsible for con necting a request to a controller A controller in Rails is just a regular class that inherits from ActionController each public method is an action triggered by some thing the user does ActionView is there in the background but your Ruby classes don t interact directly with it Views in Rails are templates with names ending in html erb by default the exact suffix varies with the templating system ActionPack and ActiveRecord do most of the work in Rails ActiveSupport Rails includes a large number of extensions to the Ruby core classes It also includes libraries to handle internationalized text helpers for working with times and dates and lots of other things A lot of these smaller features aren t necessarily tied to web devel opment Date time math crops up in a
328. tains a single no op test case Download introduction_to_rails output restaurant_test rb require test_helper class RestaurantTest lt ActiveSupport TestCase Replace this with your real tests test the truth do assert true end end There are two ways to run this test directly or through Rake The Rake approach is the simplest Download introduction_to_rails output rake test txt jruby S rake Cin code introduction_to_rails rouge Loaded suite gems rake 0 8 7 lib rake rake_test_loader Started Finished in 0 044 seconds 1 tests 1 assertions 0 failures O errors Without any parameters this command will run all the tests You can run just unit tests or functional tests by using the target test units or test functionals On UNIX you can narrow things down to one file or even one test case by adding something like TEST test unit restaurant_test ro or TESTOPTS name test_can_create_restaurant to the command line this copy is P1 0 printing Jan BUILDING OUR MODELS lt 114 The second way to test the components of your Rails app is just to run a test file directly from the jruby command This avoids the overhead of rake and is usually a bit quicker Download introduction_to_rails output jruby single test txt jruby Itest test unit restaurant_test rb Loaded suite test unit restaurant_test Started Finished in 0 292 seconds 1 tests 1 assertions 0 failures O errors Now that we have succe
329. take it in segments First we need to bring in both the Ruby Test Unit libraries and the Java JUnit ones Download beyond_unit_tests junit_integration test_unit_junit rb require test unit require test unit collector require test unit ui testrunnermediator require java java_import junit framework TestCase java_import junit framework AssertionFailedError Now we can define the JUnitAdapter class whose run_tests method we just called from Java Download beyond_unit_tests junit_integration test_unit_junit rb class JUnitAdapter def initialize test_result test_result test_result end def run_tests Dir test _test rb each do f load f end this copy is P1 0 printing PLUGGING INTO JAVA lt q 235 Test Unit AutoRunner new false do runner runner collector collect_all_test_unit_classes runner runner report_results_to_junit end run end end The main method run_tests will first load all relevant files from the test directory and then we hand them off to Test Unit s AutoRunner class to run This class uses a common Ruby idiom for customization its new method can take a block containing additional options In this case we re specifying how Test Unit should search Ruby s memory for tests and how it should report results while the tests are running You ll notice we re leaning on a couple of helper methods collect_all_test_ unit_classes and report_results_to_junit
330. td gt lt td gt lt link_to Show review gt lt td gt lt td gt lt link_to Edit edit_review_path review gt lt td gt lt td gt lt link_to Destroy review confirm gt Are you sure method gt delete gt lt td gt lt tr gt lt end gt lt table gt lt br gt lt link_to New Review new_review_path gt Report erratum this copy is P1 0 printing Januc 1 y for Shohei Tanaka OPEN TO THE PUBLIC After reviewers have gone to all the trouble of writing their reviews it would be nice for the general public to be able to read and comment on them Add the following two actions to the GuideController Download introduction_to_rails rouge app controllers guide_controller rb def review review Review find params id comment Comment new end def comment_on_review review Review find params id review comments create params comment comment Comment new flash notice Comment created render action gt review end The code should look pretty unsurprising since it s similar to what we did for viewing restaurants The final view which is in app views guide review html erb is similarly straightforward Download introduction_to_rails rouge app views guide review html erb lt h1 gt lt review title gt lt h1 gt lt p gt lt b gt About lt b gt lt review restaurant name gt lt p gt lt p gt lt b gt By lt b gt lt
331. te space quotes etc ARBITRARY_END_MARKER Notice that you can enclose Ruby strings in either single quotes or dou ble quotes Double quotes have a few more bells and whistles such as the simple backslash escape sequences common to many languages r n Ruby supports two more kinds of string literals that can save you a lot of extra backslashes and quote marks The first is the style quote which lets you in effect choose your own quote marks The second is a multiline string called a heredoc It includes everything between the two occurrences of your ARBITRARY_END_MARKER 1 http ruby doc org core classes String hAtm Report erratum 0 printing Jar A CLOSER LOOK lt 282 Symbols Ruby s Symbols are a heritage from Lisp They re a bit like read only Strings The difference goes deeper than that though When you create a Symbol by typing a name that begins with a colon there will exist only one instance of that symbol no matter how many times you use that name in your program def exact_same_object a b asad pid end All occurrences of the same Symbol share the same instance a_class String another_class String i exact_same_object a_class another_class gt true Each string literal creates its own separate instance of String fake_cheese String cat_toy String exact_same_object fake_cheese cat_toy gt false You ll typically use Strings fo
332. terator new iter should_receive hasNext and_return false set Set new set should_receive iterator and_return Citer map should_receive entrySet and_return set HashMap new map size should 0 end end this copy is P1 0 printing MOCKING AND STUBBING What s going on with those lines that say Map new Iterator new and Set new Shouldn t it be illegal to create instances of those since they re just interfaces Behind the scenes JRuby is creating anonymous Java classes that implement the interfaces That connection is actually the key to how Java mocking works in JRuby Go ahead and run the test with RSpec jruby S rspec hashmap_spec rb Finished in 0 574 seconds 1 example 0O failures If the Java code fails to make the sequence of calls we ve specified RSpec will print a failure message Add the following incorrect expecta tion just after the line containing hasNext iter should_receive next Now try to run the test again jruby S rspec hashmap_spec rb F Failures 1 Java JavaUtil HashMap can be created from an empty Map Failure Error iter should_receive next org jruby gen InterfaceImp1639549753 a00a64 next any args expected 1 time received 0 times bad_hashmap_spec rb 17 3 1 Finished in 0 377 seconds 1 example 1 failure See the bit in the error message about expecting next with any args For this example we didn t care about what arguments Java p
333. that s running you can visit http localhost 8080 to try the appli cation before deploying it This is a nice all in one way to distribute and deploy or run your web application in a single file 7 5 Wrapping Up We covered a lot of ground in this chapter We brought together the strengths of Rake and Ant the dominant build systems in the Ruby and Java universes We took a peek at how to deploy JRuby software using Maven for Java projects that depend on it Finally we saw how to deploy Ruby based web applications like the Rails app we built in an earlier chapter onto Java servers Earlier in the chapter we hinted at testing JRuby applications Let s come back to that now JRuby provides several great ways to test not only your Ruby code but also your legacy Java code Join us in the next chapter to find out how Chapter 8 It turns out that Ruby is a great language for testing both Ruby and Java code And that s where we re going to start our exploration of soft ware testing at the code level In this chapter we ll look at the Ruby tools test harnesses and mocking libraries that you re most likely to encounter as you consider how to test individual Java or Ruby classes For the next chapter we ll branch out into integration testing connect ing Ruby to Java test frameworks and other related topics Ola Says The Ruby community has had a reputation for being religious about testing for a long time and there
334. the fit and finish level of detail such as setting up your PATH environment variable to make finding JRuby easier The JRuby team currently maintains installers for Windows and Mac machines If you re on Linux your distribution may package its own JRuby build For example on Ubuntu you can type this sudo apt get install jruby Most Linux distributions don t upgrade to the latest JRuby release the instant it comes out If you want to stay with the latest and greatest you might prefer installing from an archive instead we ll describe how to do this later Using the Ruby Version Manager The Ruby Version Manager RVM is a tool for Mac and Linux that can automatically install and switch among several different versions of 4 http jruby org download Report erratum INSTALLING JRUBY Ruby at once A large part of its audience consists of Ruby library developers who need to test their software in many different Ruby environments Even if JRuby is the only Ruby you plan on using you may want to take a look at RVM As of this writing here are the JRuby versions RVM knows about rvm list known grep jruby jruby 1 2 0 jruby 1 3 1 jruby 1 4 0 jruby 1 5 5 jruby head The last item jruby head is a build from the latest bleeding edge source code The one before it jruby 1 5 5 or just jruby is the latest stable release as of this writing Here s how you d install and start using 1 5 5 rv
335. the block via yield or call the block runs with whichever parameters were passed to it Blocks are used all over the place in Ruby and you will see many of them in this book If this syntax is new to you it s worth taking a minute to type in the previous examples and make a few experimental changes to the code to see how blocks work Exceptions Like Java Ruby has exceptions Unlike Java Ruby s exceptions are all unchecked The Ruby equivalent of Java s try catch finally is begin rescue ensure Curiously Ruby also has keywords named try and catch but they are not related to exceptions at all The following code raises an exception and then rescues it begin puts Everything s fine so far raise I m raising an exception right now puts Ruby will never run this line rescue gt e puts My exception says fe end This example raises a string which Ruby is kind enough to wrap up in a RuntimeError object for us You can define your own exception types if you like Here s a more advanced example with our own exception class and multiple rescue clauses Ruby examines these from top to bottom so make sure you order them from specific to general class ImCold lt RuntimeError end begin raise ImCold Brrr it s chilly in here rescue ImCold gt e puts I m cold f e rescue Exception gt e puts Some exception other than ImCold was thrown ensure puts This will _always_ print kinda like Java s fi
336. the right Java method aka target method e Coercing casting or otherwise converting arguments to appropri ate types Let s say you re attempting to call the foo method on class X First JRuby will use Java reflection to search for all public and protected methods named foo for X and its superclasses Child classes methods override their parents just as in pure Java Next JRuby narrows down the list to just the methods that match the number of arguments you re passing in including methods with variable argument lists PARAMETER TYPES lt 291 Ruby Type Java Type Notes i 1 nullt Il NilClass A null reference Use SomeJavaClass nu o calla nil specific overload with a null reference TrueClass true A primitive or boxed boolean FalseClass value false Any primitive or boxed Fixnum numeric int java lang Float etc Matches the widest type available force to a specific type if you need a different overload Any primitive or boxed Float floating point value float java lang Double etc Matches the widest type available force to a specific type if you need a different overload Bignum java math BigInteger Requires converting character by character String java lang String which is slow Consider pre converting or just using Java Strings Figure B 1 Basic types When there s more than one matching overload JRuby looks for the best fit based
337. them in the wild Ooctal By now you ve seen several cases where you can throw together a Ruby script to parse a file given to you in some ad hoc text format Up until now we ve been assuming that newline characters are what separates one record from the next But there s no reason it can t be a different character You can specify the record separator by passing O with an optional octal byte value For example if you want to split a file on the letter q you d specify 0161 the octal value character code for q Lets see what that looks like in action echo fooqbarqbaz jruby 0161 e 3 times p gets fooq barq baz n Notice that the final string still gets the standard n line terminator since there s no final q character to close out the string If you leave out the octal value JRuby will use a record separator of 0 the null byte If you specify 00 or provide a character code outside the 8 bit ASCII range JRuby switches to paragraph mode with a record delimiter of two newline characters n n a n and p These flags enable various line processing options for processing data files or console input The n flag runs your specified script in a loop At the top of the loop JRuby implicitly calls gets to wait for the user to Report erratum COMMAND LINE OPTIONS lt d 304 2 Charlie Says g f These flags can be especially useful for processing a data file quickly They reduc
338. thing to do is just dump all the files containing your various Rake tasks into a directory called rakelib just below the direc tory where your Rakefile sits Rake will automatically look for and load all the tasks from there This is the technique we used for defining the tasks in this example Namespaces As your Rakefile grows you may start running out of good names for tasks You end up with either synonym syndrome tasks named build generate create and so on or unpalatably long names generate_class_ files generate_jar_file generate_docs and so on Report erratum Fortunately Rake offers a better way to avoid collisions namespaces The idea is to partition your tasks into logical groups jar for compila tion tasks doc for documentation Then you can have both a jar create and a doc create with no ambiguity It s a little bit of overkill to use namespaces for a project as small as this one but just for fun let s see what it would look like jar namespace jar do tasks for class and Manifest go here desc Compile the Java code task compile gt Pitcher class Catcher class desc Create a jar file from the compiled code task create gt compile Manifest do sh jar cfm baseball jar Manifest Pitcher class Catcher class end end javadoc namespace doc do directory doc desc Build the documentation task create gt doc do sh javadoc d doc java end e
339. thod just as if they belong to a regular Ruby object Behind the scenes the jmx gem is ferrying these calls to the remote process and delivering the answers to us This monitoring process does not know or care what language the main program is written in You could easily command a stable of Java appli cation servers full of Ruby and non Ruby applications all from the same remote client E 3 Wrapping Up Over the last few pages we ve looked at a couple of different ways you can use JRuby to keep your system running smoothly We wrote a Ruby script that runs like a batch file only with the full power of a program ming language behind it And we grabbed some runtime statistics from a web application without having to implement a separate administra tive user interface Download guis limelight bookie stages rb stage default do default_scene bookie title Bookie location 200 25 size 400 400 end if ENV BOOKIE_DEV stage devtool do default_scene devtool title Dev Tool location 50 25 size 100 100 background_color transparent framed false end end Download guis limelight bookie production rb module Production attr_reader chapter_contents def production_opening require redcloth chapter_contents title gt 1 text gt end end Appendix F APPENDIX F LIMELIGHT EXAMPLE SOURCE Download guis limelight bookie bookie props rb root do center do chapter_list id
340. thods including this one javap waveform public static org jruby runtime builtin IRubyObject method__2 RUBY rms waveform org jruby runtime ThreadContext org jruby runtime builtin IRubyObject org jruby runtime Block As you can see these methods are meant for JRuby s consumption only It would be possible to whip up all those private data structures and pass them in But as we ll soon see there are much more pleasant ways to accomplish this task A SIMPLE COMPILED EXAMPLE a Charlie Says v When you compile several Ruby classes with the java option the generated Java classes all share one instance of the Ruby runtime This is similar to the SINGLETON context we discussed in Chapter 3 Ruby from Java Embedding JRuby on page 60 so the same warnings about thread safety apply Calling Compiled Ruby from Java Let s back up for a second The purpose of the regular jrubyc command is to compile Ruby code so that Ruby can use it Trying to call that Ruby specific compiled class from Java is cutting against the grain In Chapter 3 Ruby from Java Embedding JRuby on page 60 we saw a much more straightforward way of calling Ruby from Java JRuby Embed If we insisted on doing everything by hand there s no need as we ll soon see here s how we might use the embedding API to drive our Ruby class Download compiler waveform WaveformWrapper java import org jruby embed ScriptingContainer public cl
341. ths Arrays asList Jib String expr require git n Git openC diffC HEADA HEAD System out printIn container runScriptlet expr You may be wondering how this works Let s examine the signature of JRuby s runScriptlet first java lang Object runScriptlet String expression The return value is the result of the last expression in the Ruby code we passed in converted to a Java Object But what is the value of the following line Git open diffC HEAD HEADA It s a Ruby Array with one Git Diff DiffFile element per file in the Git changeset How is Java supposed to work with this Ruby object Luckily all we re doing is passing the result to printin which doesn t care about the underlying type as long as it implements toString As we discussed in Chapter 2 Driving Java from Ruby on page 31 JRuby defines this method for us as a wrapper around the Ruby equivalent to_s This example should produce the same output as the previous one all we re doing is shifting the printing burden from Ruby to Java Even tually we ll be handing that data back in a format that Java can pick apart But first let s add a little flexibility It would be nice to be able to see the difference between any two revi sions not just the two most recent ones So we ll have the user supply two Git revision identifiers on the command line and we ll pass them into Ruby together as a single Java object As we
342. til concurrent Executors callable myproc callable call This approach is suitable only for simple interfaces If an interface has ten different methods in it that poor little Ruby block is going to have to understand ten different ways in which Java might call it In those cases you re best off using the class approach described earlier One other thing to note about the block approach is that the interface passed into the Java world isn t quite a first class citizen For instance the code on the other side of the wall won t be able to use features like introspection to interrogate your Ruby code 2 8 Troubleshooting It happens to the best of us You re ready to tie together your master piece and instead of passing tests you get a 20 line stack trace Here are some of the errors you might see on your path to JRuby bliss Report erratum TROUBLESHOOTING NameeError If your import fails with a NameError like this Download java_from_ruby name_error rb require java java_import com example Foo gt eval 1 in include_class cannot load Java class com example Foo NameError there are a couple of things you can check First try the obvious make sure your classpath contains the directories where your Java classes live Next make sure the directory structure matches the Java package structure If your Java class is part of the com example pack age the class file needs to be nested in a com example
343. to get into a bit of compiler nerd theory COMPILER 101 Running Without a Compiler Most implementations of the Ruby programming language run pro grams directly from the source code by following a series of steps 1 Read the text of the program from an rb file on disk 2 Parse the source code into an in memory form called an abstract syntax tree AST 3 Execute interpret the AST directly by walking through its struc ture and performing the instructions at each node The first two steps happen when the application first starts The third happens continually while the program is running This is how nearly all Ruby development happens Most Ruby gems ship as a collection of rb files which remain in their unaltered source form straight through deployment Most Ruby developers never need to write or run anything but rb files JRuby supports this method of running programs of course Interpret ing code works just fine for most applications and it s the most direct route from source code sitting on disk to a running program However interpreters are generally not the fastest way to execute code At each node of the AST JRuby s runtime must make a decision about how to react make several calls to the Java runtime and eventually perform the requested action Is there a better way Introducing the Compiler Most interpreted languages that need to perform well eventually incor porate a compiler A compiler gen
344. to accidentally kill your Ruby runtime can end up with a call that never returns Fortunately this is a bit of an extreme case Just keep in mind the hazards of multithreaded programs as you re writing your code Single Threaded So the first mode guaranteed a single Ruby runtime and the sec ond introduced some thread safety The third mode does none of the above Each time you create a ScriptingContainer with the SINGLETHREAD option you actually create a new context This new context is com pletely unconcerned with concurrent access Everything rides on you the programmer to access the container from one thread at a time In truth this kind of context is not such a dangerous beast if used in a controlled environment For example if you are running a servlet that spins up multiple threads you can safely spawn one SINGLETHREAD ed ScriptingContainer per servlet thread in Servlet init Some configurations of the jruby rack project use this strategy Ruby Version JRuby supports both Ruby 1 8 and Ruby 1 9 syntax and semantics By default a new ScriptingContainer uses Ruby 1 8 mode but it s quite easy to use 1 9 instead container setCompatVersion org jruby CompatVersion RUBY1_9 8 For more information on what some of these hazards are see Ousterhout s Why Threads Are a Bad Idea for most purposes at http home pacbell net ouster threads padf Report erratum 0 printing Jan EMBEDDING STRATE
345. to the database You signal a failed validation by adding one or more errors to the errors attribute of the model instance If you add no errors ActiveRecord will consider the validation a success We strongly recommend validates_each over the low level mechanisms If you make a mistake with the latter your other validations might not run Report erratum 1 0 printing January 2011 RUBY DATABASE FRAMEWORKS lt 145 As you can see the possibilities for validation are considerable You can go totally crazy and validate each and every aspect of the data before it ever gets into the database But one detail is missing When should the validations actually run There are some alternatives here The basic rule is that during regular model usage you will see more about this in the next section ActiveRecord will run your validations just before an object gets saved to the database If you need more control you can call the valid on a model instance at any time Model Usage You have now seen most of the important parts of the ActiveRecord puzzle except for how to actually use it that is In keeping with the blogging theme we ve started lets take a look at some examples of how to create blogs and add posts Download databases ar_usage rb require rubygems require active_record b1 Blog new author gt Ola Bini b1l title My first blog b1 save Blog create title gt My second blog b2 Blog find
346. ts own props and players During development you ll spend most of your time in scenes laying out props and players Limelight s other big feature is its style system which is influenced by the Cascading Style Sheets CSS used on web pages When you con struct a prop you change colors borders gradients and other visual properties by editing a style file Warning this can lead to addictive hacking sessions where you spend hours tinkering with your app s appearance But it also gives you a huge level of customization We ll be counting on that as we try to make the Limelight version of Bookie look like the other versions Like Monkeybars Limelight is an opinionated software framework with a convention over configuration aspect inspired by Rails When you create a new production or join someone else s the code will have a familiar directory layout and naming convention Before we get to writing apps we d like to show you how to launch Playbills the gallery of demo productions that ships with Limelight jruby S gem install limelight jruby S limelight open One of the more compelling demos in the gallery is Limelight Docs the API browser interactive tutorial This is more than just a collection of passive code snippets you can edit and rerun the examples right there in the app Of course both Playbills and Limelight Docs were written using Limelight 6 Is that what directors think of their actors Report
347. tum this copy is P1 0 printing January 2011 RUBY TEST FRAMEWORKS gt E Ola Says Behavior Driven Development BDD is one of the newer buz zwords It s a technique that extends and builds on Test Driven Development TDD Rather than focusing on a series of pass fail checks of individual classes BDD describes the behav ior of a system as a whole in terms of specifications or examples Tests become information that the entire team even nonpro grammers can understand and use to make decisions about the project The first BDD framework was actually written in Java and was called JBehave Since then many BDD frameworks have sprung up several of them using the language features of Ruby to emphasize clarity in specifications test soec and RSpec are the two major frameworks for Ruby but you can practice BDD even in a standard unit testing framework It s just a question of style RSpec encourages you to think of each expectation as an example doc umenting the behavior of a specific piece of code An example can be as simple as one low level method invocation or as far ranging as a mouse click affecting several classes You organize groups of related examples into contexts The describe method introduces a context and the it method wraps each individual example Ready to get started with RSpec First grab the gem and then we ll talk code jruby S gem install rspec Successfully installed rspec core 2 0 1
348. type easily Java Fred getClass getNameQ gt java lang String Ruby Fred class name gt String As you can see the Fred object has a type called String in both Java and Ruby Each type supports a specific list of operations for strings that d include combining searching capitalizing and so on In both languages trying to take the square root of a string would cause an error you d have to convert it to a different type first For this reason both Java and Ruby are known as strongly typed languages We should mention one other thing about variable declarations In Ruby there s no need to ever declare a variable without giving it a value as is sometimes done in Java Instead a variable is implicitly declared the first time it is given a value What happens if you refer to a variable before it has been assigned a value a l puts a gt gt 1 puts b gt gt undefined local variable or method b for main Object NameError While we re on the subject of variable visibility Ruby s if statement has the curious property that variables inside it are visible from outside In programming language parlance it doesn t introduce a new scope cat The cat lives outdoors if 2 2 4 cat but can be seen indoors dog The dog lives indoors end dog but can be seen outdoors MEET RUBY lt 274 puts cat gt gt The cat lives outdoors but can be seen indoors p
349. u can t figure out how JRuby is finding that file you can turn on logging to show all locations searched along with failed and successful loads You may be surprised what you see for large applications Report erratum D 1 Appendix D We ve spent a lot of time in this book talking about calling Java from Ruby and vice versa And with good reason it s one of the main reasons people come to JRuby You may be wondering though are you stuck in the Java universe if you go with JRuby Not at all JRuby is one of the many Ruby implementations that can call straight into C code in fact it s one of the best Foreign Function Interface There are several reasons you might want to call into native code from JRuby For example e You may need to take advantage of some specific feature of your operating system e A piece of hardware you re using may come with no manual and no source code just a DLL e Your Ruby code might be part of a larger program with parts writ ten in different languages e You may be using a Ruby gem for image processing XML parsing or data access that leans on C code internally How do you connect to external code in these situations Extension API In the old days you d write a small piece of glue code in C that would wrap the external code with a Ruby like interface This approach using Ruby s extension API is still supported in regular Ruby and is gradually making its way into JRuby as
350. ubeus Report erratum RUBEUS lt q 247 e People who already know Swing will experience a quick learning curve and improved productivity e Rubeus s underlying code base is smaller than other frameworks This simplicity leads to easier maintenance Are you convinced this idea could work or at least willing to indulge us for a few pages Let s look at some code Download guis rubeus bookie rb require java require rubygems require rubeus require redcloth java_import javax swing DefaultListModel java_import javax swing text html HTMLEditorKit Rubeus Swing irb The top of the file looks similar to the straight Swing example with the addition of the rubeus gem to the mix But where did all our java_imports go They ve been almost completely replaced with one line the call to Rubeus Swing iro This method makes the most commonly used Swing classes available to us You ll find much that s familiar in the rest of the application too As we said Rubeus is a short step away from raw Swing One difference that should pop out though is that all the constructors take a block This means you can lay your Ruby code out according to the structure of your GUI Here s the skeleton of the code you ll be writing JFrame new Bookie do frame frame layout BoxLayout new Y_AXIS JSplitPane new JSplitPane HORIZONTAL_SPLIT do JList new JScrol1 Pane new preferred_size gt 400 250 do JTabbedPane ne
351. uite lt lt s suite end end And now we ll see the TestUnitResultHandler class that s tasked with hand ing Test Unit results back to JUnit Download beyond_unit_tests junit_integration test_unit_junit rb class TestUnitResultHandler def self run suite ignored nil runner new suite runner instance_variable_set result_handler result_handler runner start end def initialize suite io STDOUT if suite respond_to suite suite suite suite else suite suite end end def start mediator Test Unit UI TestRunnerMediator new suite mediator add_listener Test Unit TestResult FAULT amp method add_fault mediator add_listener Test Unit TestCase STARTED amp method test_started mediator add_listener Test Unit TestCase FINISHED amp method test_finished mediator run_suite end end opy is P1 0 prin PLUGGING INTO JAVA lt 237 This code is the public interface to the class Test Unit will call the static run method and expect us to create and launch an instance of the class You ll see that we re adding callbacks to something called a mediator which you can think of as a test step watcher Each time something interesting happens like a step failing or a test suite com pleting Test Unit will notify the mediator which will in turn notify us Inside the three callbacks we just need to hand the results off to JUnit Download beyond_unit_tests junit_integration test_u
352. und Download introduction_to_rails rouge features step_definitions restaurant_steps rb Given AI am logged in as an admin do Administrator create username gt admin password gt admin basic_auth admin admin end lt q 227 ACCEPTANCE TESTING 228 Because Rouge users including administrators are stored in the data base we have to create a new account before we can log in Then we can use Webrat s basic_auth method to specify the login credentials We re almost ready to run the tests We just have a bit of housekeeping to do first Add the following to the end of your Gemfile Download introduction_to_rails rouge Gemfile group development test do gem webrat gem cucumber rails gem cucumber gem rspec rails gt 2 0 end Now run the following commands in the project directory jruby S bundle install jruby script rails generate cucumber install rspec webrat jruby S rake db migrate This will install the pieces Webrat needs to talk to your Rails app and generate a few Cucumber specific configuration files in the project directory We ll need to make a couple of customizations on top of this configuration Create a file in features support called webrat_config rb and put the following code in it Download introduction_to_rails rouge features support webrat_config rb Webrat configure do config config mode rack end require webrat core methods Wo
353. und the scaffolding interface and create at least one new administrator for later As you might notice there are a few problems with this simple scaffold The biggest one is that we re displaying the password in plain sight Let s fix that Open the view file at app views administrators _form html erb and change text_field to password_field in the following place Download introduction_to_rails rouge app views administrators _form html erb lt div class field gt lt f label password gt lt br gt lt f password_field password gt lt div gt Now modify app views administrators index html ero and app views admini strators show html erb to show asterisks instead of passwords To do so replace occurrences of this administrator password with this administrator password gsub this copy is P1 0 printing RESTAURANT ADMINISTRATION 101 lt 120 Note that these changes affect only the display of the password not the storage We re still keeping the password in the database in clear text which is a good way to get our site compromised Password hashing is a fascinating topic but definitely one for another day We encourage you to check out a Rails security package such as Devise for your own apps With a simple but functional account creation page in place we can move on to the rest of the administrative section The Restaurant ad ministrative user interface is much simpler jrub
354. universally beloved by Ruby developers JRuby and Swing can provide just the sort of happy ending to the Ruby GUI development story we ve all been waiting for To give you an idea of the feel of GUI development on JRuby we re going to write one application using four different frameworks What sort of application you ask It needs to be something short enough to fit in a chapter but complicated enough to show you some of the trade offs you ll need to make in your own projects As we were putting this book together the answer came to us how about an application to write and organize the chapters for a book We re going to build a glorified text editor that lets you write a series of chapters in a simplified markup language and then preview the final pages Ready Let s get started 10 2 Swing The first Ruby framework is no framework at all We re going to just use the Java integration features we talked about in Chapter 2 Driving Java from Ruby on page 31 and script a solution using the Swing APIs directly Seeing the Swing solution first will be a great base to build on for understanding the benefits and trade offs of the other frameworks Before we get into the code let s take a look at where we re headed We want to end up with something like Figure 10 1 on the following page On the left side is a list of chapters We have two so far and can add a third one at the end by clicking Add Chapter The right side of the window
355. ur aim for this chapter to give a quick overview of Ruby from a Java pro grammer s perspective For a much more detailed look see a dedicated book on Ruby such as the Pickaxe Programming Ruby The Pragmatic Programmers Guide TFHO8 Meet Ruby We re going to start with the high level view as we answer the question What is Ruby like Ruby Is Dynamic and Strong Ruby is often described as being a member of the family of dynamic languages What do we mean by dynamic Computer language enthu siasts use the term to explain type systems A statically typed language like Java knows the types of a program s variables at compile time long before the program runs With a dynamic language a variable s type can t usually be known until runtime Consider the following similar looking snippets Jana int price price 10 OK price a chicken compile time error Ruby price 10 OK price a chicken OK MEET RUBY lt 4 273 The main difference that immediately sticks out is that the Java vari able has a declared type and the compiler forces assignments to con form to that type By contrast you don t declare variables in Ruby you just start using them It may be tempting to think that Ruby has no types at all but nothing could be further from the truth Even though variables don t have types in Ruby values most certainly do In both Ruby and Java you can find out a value s
356. urant his review goes with Let s fix that First we need to tell our controller to grab a list of all the restaurants so the view can show them in a selec tion box Open reviews_controller ro and add a single line to the beginning of both the new and edit actions We ll just show the new action here Download introduction_to_rails rouge app controllers reviews_controller rb def new G restaurants Restaurant alphabetized G review Review new respond_to do format format html new html erb format xml render xml gt review end end Restaurant alohabetized will be a sorted list of restaurants We say will be because this is new functionality we need to add to the Restaurant model What should this method look like Well we could use bread and butter techniques like Ruby s sort method def Restaurant alphabetized Restaurant all sort r r name end This code would return the correct results but it ignores the fact that we already have a screamingly fast data sorter sitting underneath our app the database So should we construct an entire SQL query our selves and send it to the database ActiveRecord offers us something much better relations To add an alphabetized relation to the Restau rant model modify restaurant rb to look like this the new code is in the second to last line Download introduction_to_rails rouge app models restaurant rb class Restaurant lt ActiveRecord Base validates_pres
357. uris URI new C uploads URI new images URI new stylesheets uris sort map u u to_string gt images stylesheets uploads JRuby maps the two concepts together so that you can sort Java objects inside Ruby collections this copy is P1 0 printing CALLING OVERLOADED METHODS Edge Cases Before we move on let s dip our toes into a few of the more obscure conversions JRuby adds the to_proc Ruby method to Java Runnables so they can be passed around as blocks of code in Ruby Here s a rather contrived example that hands off a Java thread to a Ruby one Download java_from_ruby special_cases rb runnable java lang Thread new run_it runnable to_proc Thread new amp run_it Java InputStreams and OutputStreams can be converted to Ruby IO ob jects with the to_io method Download java_from_ruby special_cases rb java_out java lang System out to_io java_out lt lt Hello from JRuby You can catch Java exceptions in a Ruby rescue clause Download java_from_ruby special_cases rb begin java text SimpleDateFormat new nil rescue java lang Nul1PointerException puts Ouch end Believe it or not there is an overall theme to this parade of examples simplicity JRuby supports so many different ways of passing data into Java precisely so that your Ruby code can be as lucid as possible Rather than trying to memorize every edge case we recommend you take one more glance over the
358. use the latest installed version Warbler Configuration So you ve come across part of your application that Warbler either omitted or didn t package properly now what Fortunately configuring Warbler is almost as easy as building the war in the first place The first thing you ll need to do is generate a configuration file The warble config command does this jruby S warble config cp JRUBY_HOME 1ib ruby gems 1 8 gems warbler 1 1 0 warble rb config warble rb As you can see Warbler copied an example config warble ro file for you to modify The basic contents of the file look like this Warbler Config new do config You modify the configuration in here lots of settings end We encourage you to have a look at the full config warble rb file It s heav ily documented demonstrates all the available configuration options and provides reminders about Warbler s default behavior Let s consider a few of the more common settings Say you have some additional files and directories that need to go in your war file The config dirs setting near the top of config warble ro contains an array of directories to which you can easily add your own config dirs w app config lib log resources vendor tmp Report erratum PACKAGING FOR DEPLOYMENT lt 194 If you want to include or exclude additional files you can do that with config includes and config excludes Both take either arrays of filenames or R
359. uts dog gt gt The dog lives indoors but can be seen outdoors One consequence of Ruby s dynamic nature is that many errors that would be considered compile errors in Java code are not revealed until you run your program Everything Is an Object Youll recognize many of Ruby s object oriented features from your ex perience with Java Objects are instances of classes which can be built in or user defined Objects embody both state instance variables and behavior methods A program manipulates objects by calling methods which Ruby also refers to as sending messages However Ruby takes this notion further than other object oriented lan guages including Java How Well its common to hear that in Ruby Everything is an object That includes the primitive built in types that come with the language 123 to 1 gt 123 123 t0o s gt 123 true to_s gt true nil to_s r e 123 nil gt false nil nil gt true Have you ever tried calling a method on null in Java Everything Has a Value As we saw in the previous section everything in Ruby is an object You can call methods on anything even things such as numbers booleans and class definitions Another universal Ruby law is that everything you do in Ruby returns a value Java makes the distinction between expressions which return values and statements which don t In Ruby there is no such distinction Everything returns a
360. value not always a terribly useful one but defi nitely something Even a class definition has a return value Report erratum 0 printing Jar A CLOSER LOOK lt 275 This feature of Ruby comes in handy with conditional expressions Con sider the following Java fragment Java String result switch getNumberFromSomewhere case 2 result twins break case 3 result triplets break case 4 result quadruplets break default result unknown break System out printin result and its Ruby equivalent Ruby puts case get_number_from_somewhere when 2 then twins when 3 then triplets when 4 then quadruplets else unknown end Since a switch statement in Java can t return a value the Java example has to set aside a variable to store the result so we can print it In Ruby cases are expressions and will return the last value mentioned in whichever branch got taken Since we don t need to save away a value in a variable it s actually possible to just pass the entire case expression as an argument to puts This looks really weird if you haven t seen it before but will soon become second nature A 2 A Closer Look Now let s take a closer look at the Ruby language We ll cover how to accomplish the most common programming tasks Along the way we ll look for both similarities and differences from Java Defining Classes Ruby is a class based object orient
361. ve new List lt GitDiff gt diffs List lt GitDiff gt invocable invokeMethod archive history new Revisions args 0 args 1 for GitDiff diff diffs System out printiInC FILE diff getPathQ System out printiIn diff getPatch JSR 223 is able to perform the same tasks for Historian that Embed Core does in a slightly less expressive notation BSF has a similar feel this copy is P1 0 printir THE NITTY GRITTY to what you saw previously so we won t show a detailed example for it Instead we recommend you use JSR 223 for non Ruby specific embed ding projects because of its official position as part of the JDK Containers and Contexts Each ScriptingContainer object that you create for embedding Ruby code has an associated context object which JRuby uses for internal book keeping By bookkeeping we mean things like the Ruby interpreter instance I O streams a special variable store and configuration options The simplest ScriptingContainer constructor creates a context implicitly for you In case you want a little more control you can specify the kind of context you want new ScriptingContainer defaults to SINGLETON new ScriptingContainer LocalContextScope SINGLETON new ScriptingContainer LocalContextScope THREADSAFE new ScriptingContainer LocalContextScope SINGLETHREAD Singleton SINGLETON the default choice creates one Ruby runtime shared by the entire JV
362. w TOP SCROLL_TAB_LAYOUT do JTextPane new JEditorPane new end end end JButton new Add Chapter frame visible true end Report this copy is P1 0 printing Jar RUBEUS lt 4 248 Note that the JSplitFrame gets added to the JFrame without our having to call the add method ourselves Also take a second look at this line frame layout BoxLayout new Y_AXIS In pure Swing code we would have had to say something like this instead frame layout BoxLayout new frame content_pane BoxLayout Y_AXIS Rubeus knows that a layout manager always needs its frame s con tent_pane to be passed in so it takes care of that detail for us It also provides Y_AXIS as a shortcut to BoxLayout Y_AxIS Less ceremony more readability The next piece of code goes just inside the JSplitPane block Download guis rubeus bookie rb chapters JList new DefaultListModel new chapters selection_mode ListSelectionModel SINGLE_SELECTION class lt lt chapters def add_chapter count model size model add_element count 1 selection_model set_selection_interval count count end end chapters add_chapter This looks just like the chapters section from before with one difference We re defining chapters as an instance variable now rather than as a local variable This is because the chapter list belongs to a very deeply nested block but needs to be visible from a higher level block later The internal table o
363. wave puts waveform rms gt gt 0 706126729736776 this copy is P1 0 printing A SIMPLE COMPILED EXAMPLE What else can we do with the compiled class file Not much It might be tempting to try to drive this code from Java like this public class WaveformNaiveTest public static void main String args double triangleWave 0 0 1 0 0 0 1 0 0 0 waveform w new waveform triangleWave System out printIn w rmsQ Unfortunately that doesn t work javac cp jruby jar WaveformNaiveTest java WaveformNaiveTest java 4 cannot find symbol symbol constructor waveform double location class waveform waveform w new waveform triangleWave A WaveformNaiveTest java 5 cannot find symbol symbol method rms Q location class waveform System out printIn w rmsQ A 2 errors Java was able to find the waveform class note that the capitalization follows the Ruby filename but none of its methods Consider the con structor Java will be looking for a constructor taking an array of dou bles Ruby parameters can be anything and we haven t yet discussed how to tell JRuby what parameter types to write into the class file The mismatch doesn t stop at the constructor This Java code is expect ing the waveform class to have an rms method taking no parameters and returning a double But the class file has no such method If you use javap to look at the waveform class you get a long list of me
364. we write this book FOREIGN FUNCTION INTERFACE lt 310 The advantages of the extension API are its speed and its status as the official way to plug C into Ruby The disadvantage is that there s an extra layer of glue code This layer takes time and effort to write Moreover it has to be compiled specifically for the end user s platform often by the end user at installation time Ruby Standard Library Ruby has evolved a couple of libraries that let you skip the middleman and talk straight to the external code you want Two of these Ruby DL and Win32API have become part of the Ruby standard library Because C functions must declare their argument and return types Ruby code using one of these techniques has to be decorated with a little extra information about data types The Ruby syntax for these decorations varies but it s never felt flexible enough for C or comfort able enough for Ruby Worse there are subtle differences across Ruby versions Ruby DL and Win32API are only partially supported in JRuby We mention them mainly to set the stage for the preferred way of calling out to C the FFI library FFI FFI short for Foreign Function Interface began as part of the Rubinius project an advanced implementation of the Ruby language 2 We ll look at a couple of longer examples in a moment But just to get a feel for FFI here s how you d call the pow function in the C runtime library Download ffi pow
365. width 1 left_margin 8 right_margin 8 bottom_margin 8 font_size 16 font_face times edit_pane width 100 height 90 left_margin 8 right_margin 8 bottom_margin 8 l Styles of styling text pi top_margin 3 bottom_margin 3 border_width 1 border_color blue I br i strong font_style bold em font_style italic 7 is P1 0 print APPENDIX F LIMELIGHT EXAMPLE SOURCE lt 327 Download guis limelight bookie bookie players add_chapter rb module AddChapter def mouse_clicked e contents production chapter_contents title contents length 1 to_s new_content title gt title text gt contents lt lt new_content scene chapter_list repopulate end end Download guis limelight bookie bookie players bookie rb module Bookie prop_reader chapter_list dual_pane prop_reader preview_pane edit_pane prop_reader preview_tab edit_tab def scene_opened e chapter_list repopulate chapter_list select 1 true dual_pane edit end end Download guis limelight bookie bookie players chapter rb module Chapter attr_accessor model def mouse_clicked e scene dual_pane current_chapter model end def select style background_color sky_blue end def deselect style background_color white end end Download guis limelight bookie bookie players chapter_list rb module ChapterList def repopulate remove_all production scene production build do pr
366. with the test code we ve already written Extracting our code into a macro is easy First we define a new Ruby module and drop all our test code into a single method inside that module this copy is P1 0 printing RUBY TEST FRAMEWORKS lt 4 210 Download testing_with_jruby shoulda map_shoulda rb require rubygems require shoulda require java java_import java util HashMap java_import java util TreeMap java_import java util concurrent ConcurrentHashMap module MapMacros def should_behave_as_a_map Everything inside the New hashmap context from before excepts the first setup block and the outermost pair of Context end lines end def self included type type extend self end end What s the self included method there for This is a bit of Ruby book keeping to ensure that any Ruby class using this module has access to the should_behave_as_a_map method In particular we want to drop this module into our TestCase derived class so we can use our macro in several different contexts Download testing_with_jruby shoulda map_shoulda rb class MapTestCase lt Test Unit TestCase include MapMacros context new HashMap do setup map HashMap new should_behave_as_a_map end context new TreeMap do setup map TreeMap new should_behave_as_a_map end context new ConcurrentHashMap do setup map ConcurrentHashMap new should_behave_as_a_map end end r Shohei Tan RUBY T
367. ws CreateRestaurants migrated 0 0290s s s s s s S As you can see rake reports that it successfully created the restaurants table in the database If you don t specify an environment the migra tion will run in development mode You should see the results in the rouge_development database complete with columns for the ID name description address phone number and time stamp fields Before we proceed let s take a look at the other files Rails created for us First there s the actual model file app models restaurant ro At this stage it doesn t really look like much since it gets all the information it needs from the database this copy is P1 0 printing BUILDING OUR MODELS lt 113 Download introduction_to_rails output restaurant rb class Restaurant lt ActiveRecord Base end This seemingly empty class already has some functionality When the app starts up Rails will reach out to the database find out the col umn names name description address and phone and add methods to the class with the same names all at runtime We will add even more functionality in a minute First a brief word on testing Testing the Model Take a peek inside the test directory By default Rails generates a test file for every model and controller Let s add a few tests to demonstrate some common ActiveRecord operations Open test unit restaurant_test rb Right now it just con
368. xcerpt notice how we set the scroll pane s preferred size JScrol1Pane new preferred_size gt 400 250 do scrol1 This code replaces a wordier line from the previous example scroll_pane setPreferredSize java awt Dimension new 400 250 The final cool shortcut is the ability to pass your event handling code as a block to the constructor for the component This code goes inside the overall JFrame block just above the final end Download guis rubeus bookie rb JButton new Add Chapter size gt 40 40 chapters add_chapter frame visible true In Rubeus a block passed into a constructor can mean one of two things For a container a block is for setting up properties and lay ing out child components For an actual GUI control a block is for event handling What about containers that happen to be controls as well For those you d use a block for layout and good ol fashioned add_event_listener for events this copy is P1 0 printing RUBEUS lt q 249 MONKEYBARS lt 250 Using Rubeus is definitely a big improvement over writing your Swing application with just JRuby s basic Java scripting If you re comfortable with Swing you ll probably find Rubeus easy to use If not you might prefer a framework that s a bit further removed from the Swing API Let s take a look now at two such frameworks 10 4 Monkeybars Monkeybars is an opinionated Model View Controller MVC framework that
369. y 174 177 integration with JtestR 229 integration with JUnit 234 238 integration with Rake 177 179 Apache Derby 156 Apache Tomcat 189 application deployment 93 96 183 190 application monitoring 316 321 assertions in Shoulda 207 in Test Unit 202 associations 116 117 142 154 160 autotest 212 D n Bean Scripting Framework 70 become_java 54 Index Behavior Driven Development BDD 202 203 219 blocks 287 288 booleans 283 build tools 165 183 Bundler 103 105 108 109 C gt C functions 309 314 callMethod0 68 character encoding 295 classes annotated 53 54 93 create Java class 53 defining 275 278 from Java libraries 34 35 41 42 importing Java classes 91 model classes 134 135 141 142 153 modifying dynamically 279 native Java classes 30 subclasses in Ruby 277 utility classes 135 SCLASSPATH 40 classpath 38 40 collections 285 compilation ahead of time AOT 80 84 91 just in time JIT 80 83 302 306 stages 80 see also JRuby compiler contexts in RSpec 203 in Shoulda 209 in test spec 207 controllers 102 250 258 260 CRUD Create Read Update Delete 118 CUCUMBER JDB DEBUGGER Cucumber step definitions 222 223 225 228 stories 219 220 table driven testing 225 226 DO data file processing looping on user input 303 processing multiple files 305 record separator 303 string splitting character 305 data types dynamic vs
370. y 2 With JMX you can gather statistics about a running program either by compiling your monitoring code into it or by connecting to it remotely Because JRuby programs are running on the JVM you can find out all sorts of performance information the same way you would with a regular Java program Instead let s measure something application specific hits to the home page of a web server 3 http java sun com javase technologies core mntrmgmt javamanagement Report erratum MONITORING APPLICATIONS lt 317 The JMX Interface To provide our own custom statistics to a JMX client we ll write our own managed bean JMX s term for a data provider We could call directly into the JMX APIs using the same Ruby Java integration tech niques we ve been discussing throughout the book But we ll save some time and use the jmx gem which provides a few handy shortcuts jruby S gem install jmx Now we just create a regular Ruby class that inherits from RubyDynam icMBean Download jmx web_app rb require rubygems require jmx require rmi class HitBean lt RubyDynamicMBean def initialize name desc super name desc hits 0 end def hit hits 1 end rest of implementation goes here end So far this is just regular Ruby code We re setting up our own API that the web server will use to increment the hit count The next task is to add JMX hooks to retrieve the data The following code goes inside the
371. y a growing com munity of many thousands of Ruby developers and customers We ve FOREWORD BY BRUCE TATE regularly run into each other in places like Austin Texas and Matsue Japan Each time I ve delightfully followed the progress of JRuby This platform has delivered on every promise Consider the following e JRuby is no longer a hobby Though it holds fast to its open source foundations it now has aggressive corporate sponsorship Engine Yard has proven to be a wonderful steward and several employees are dedicated to its success Big customers have deployed major applications on JRuby open ing up the enterprise to Ruby By allowing the back office to rely on the robust reliable JVM deploying Ruby is no longer the risk it once was Each Ruby application becomes just bytecode virtually indistinguishable from other Java applications JRuby supports the Java frameworks that you need to support Sure the lower level APIs are there such as JDBC But you can also build your nimble Ruby user interface directly on your Hiber nate back end the way you want ThoughtWorks the dynamic consultancy that aggressively pushes the boundaries of developer productivity in the context of difficult problems has used JRuby to deliver both products and customer applications on far more aggressive schedules than they could have with conventional languages So JRuby is delivering on the promise of a marriage between the beau tiful langu
372. y behind the scenes optimizing hot code and leaving cold code alone Over time JRuby will incorporate more runtime information into those optimizations and long running programs well seem to magically get faster With a little insider information on JRuby though you can write code that will get the best performance out of the JIT Avoid Generating Code at Runtime For JRuby s JIT to run code needs to get hot If you re repeatedly call ing the same method for example JRuby will notice that and switch from interpreting the AST to running real JVM bytecode This will gen erally improve the performance of that piece of code many times over On the other hand if you are constantly generating new Ruby code for example by passing a string to eval or one of its cousins there will be no hot spots for JRuby to optimize If you need the flexibility of runtime Ruby code generation try to limit it to the early phases of your application s life cycle Keep evaluated code out of the critical path Prefer Smaller Methods JRuby s JIT operates on method boundaries It makes decisions about whether to JIT compile a piece of code only when it is about to be called Report erratum COMPILER 101 This works well for code with many moderately sized methods How ever when you have a few very large methods instead optimization gets trickier A large method might get called infrequently but do perform ance critical wo
373. y databases unconventional col umn names inconvenient mappings or high performance caching needs In these situations wedging exotic behavior into ActiveRecord 10 http sequel rubyforge org Report erratum would be more difficult than using a database framework that was designed for this kind of use like the Java Hibernate library The overhead of using Hibernate can be inconvenient especially for small projects That s what the Ribs project aims to change Simply put Ribs allow you to persist your Ruby objects using Hibernate It s a wrapper around the real Hibernate database framework not a port This means that Ribs is for JRuby only Using Hibernate means that you get a large amount of power out of the box But Ribs tries really hard to make its interface more Ruby like intuitive and easy to use The goal is to be able to scale Ribs from the absolutely simplest applications all the way up to extremely complex systems interacting with legacy databases Ready to get started You can install a prebuilt Ribs gem but we rec ommend building with the latest source instead Either way the instal lation will bring in Hibernate and its dependencies for you the version number in the last line may vary git clone git github com olabini ribs git cd ribs ant jar jruby S gem install rake rspec jruby S rake gem jurby S gem install pkg ribs 0 0 2 gem AAA FA HF HF HH The first thing you need to do when
374. y guessed that since both restaurants and reviews can take comments this class will need the same as gt commentable declaration that we gave the Restaurant model Download introduction_to_rails rouge app models review rb class Review lt ActiveRecord Base belongs_to restaurant belongs_to reviewer has_many comments as gt commentable end That just leaves the Comment model Download introduction_to_rails rouge app models comment rb class Comment lt ActiveRecord Base belongs_to commentable polymorphic gt true end As you can see most of the code used to specify models in Rails is self explanatory The only complication is the Comment model s poly morphic association in other words its ability to belong to more than one kind of owner Following Rails conventions we ve named the com mentable relationship after the adjective form of the Comment model s name Interacting with the Console Ideally this example has given you an idea of how to put together a few simple models in Rails Now to get a taste of how easy it is to work with these models let s fire up the Rails console and add some data to our database this copy is P1 0 printing Ja RESTAURANT ADMINISTRATION 101 4118 5 4 jruby script rails console Loading development environment Rails 3 0 0 rc gt gt mac Restaurant create name gt Chez MacDo gt gt mac comments create said_by gt Ola content
375. y ones All the method names you see in this snippet open add and close belong to Java classes That includes get_instance an alias JRuby has created for getinstance to make it fit better in the Ruby universe Some Ruby types get converted into their Java counterparts automati cally for you such as the Brought to you string Others need a little hand holding you ll see a few of those cases later Now that you ve had a chance to look through the code let s run it You ll need to tell JRuby where the external iText library lives by setting the classpath Java provides the cp option for this purpose JRuby will forward any option to the underlying Java runtime if you preface it with J Go ahead and try the following command adjusting the version number of iText to match what you downloaded jruby J cp iText 5 0 1 jar pdf_demo rb That ll create a PDF file called pdf_demo pdf in the same directory If you open it you should see something like Figure 2 3 It s not the most visually breathtaking use of the format but you get the idea SEEING JAVA THROUGH RUBY GLASSES Another Simple Example Extending a Ruby Program Let s consider another big use case taking an existing Ruby program and rewriting part of it in Java for speed Just for fun we ll make this one a GUI app albeit a trivial one We re going to build a calculator for the famous stack busting Ackermann function The Ruby code for this rea
376. y script rails g scaffold Restaurant name string address string phone string description text migration false skip You don t really need to do anything to this scaffold although in order to save screen space you may want to remove the description column from app views restaurants index html erb Since you re running in development mode there s no need to restart the web server Just visit htto localhost 3000 restaurants Finally here is the scaffolding for reviewers jruby script rails g scaffold Reviewer name string description text username string password string migration false skip Since this scaffold has a password field you ll need to change the gen erated views in app views reviewers to hide the password just like you did for the Administrator views May We See Your ID Please Right now any visitor to the site can edit the page for any administrator restaurant or reviewer Let s add HTTP Basic Authentication to control access 9 http github com plataformatec devise Report this copy is P1 0 printing Jan RESTAURANT ADMINISTRATION 101 lt 121 First we ll create a new base class for admin only controllers let s call it AuthenticatedController Download introduction_to_rails rouge app controllers authenticated_controller rb class AuthenticatedController lt ApplicationController before_filter authenticate private def authenticate authenticate_or_re
377. y sides together You can pass a Java class into your Ruby script make a Ruby class that implements extends a Java type or just use simple coercible types such as strings There is no single best approach that applies in all situations This section will break down some of the reasons why you may consider picking one strategy over another 9 http www realjenius com 2009 10 06 distilling jruby the jit compiler 10 http wiki jruby org RedBridge Configurations Report erratum P1 0 printing January 2011 EMBEDDING STRATEGIES Passing Java Data Into Ruby How do you get data into your embedded Ruby script Passing in a Java object is the easiest approach The embedded script can call the object s methods just as if they were written in Ruby You can even decorate the object with additional easier to use methods that actually are written in Ruby When is passing data into Ruby as plain Java objects not a good fit It depends on how often the Ruby script ends up calling back into Java Calling from Ruby to Java is a little slower than staying inside the Ruby universe In many cases the difference is unnoticeable but in others the type coercion cost for example copying a java lang String to a Ruby String makes this approach too slow So if your Ruby code needs to call a string returning Java method in a tight loop consider reshaping your solution a bit Perhaps the Java side could assemble a Ruby object with the da
378. y to databases work basi cally the same in JRuby Over the coming pages we ll turn our attention to relational databases as opposed to key value or other data stores You ll see how to use Ruby s more popular data frameworks and what kinds of adjustments to make when you re running them in JRuby In regular Ruby SQL libraries typically depend on a database specific C module The APIs differ widely depending on the database and frame work authors are left with the task of papering over these differences With JRuby you ll still install a binary driver for your choice of data base but at least all these drivers are written to one common API Java s JDBC standard You can call JDBC routines directly from Ruby and later we ll see a situation where you might want to do just that But it s usually more convenient to work with a higher level library It s worth keeping in mind though that all these library calls percolate down to JDBC under the hood Ruby Database Frameworks Let s take a look at the most commonly used Ruby frameworks for database connectivity From a bird s eye view there s little difference between using these in plain Ruby or JRuby RUBY DATABASE FRAMEWORKS lt 134 Ola Says In many ways both DBI and Sequel remind me of JDBC in that they try to abstract away some of the differences between dif ferent databases engines while still acknowledging that you re working with a database The
379. y what gets saved the review object s restaurant_id field and where the list contents come from the restaurants collection s id and name fields That takes care of the details of the form Let s zoom out to the over all structure for a moment Each review should feature the restaurant name prominently We can accomplish this by snazzing up the header at the top of the page 10 http api rubyonrails org classes ActionView Helpers FormOptionsHelper html Report this copy is P1 0 printing Janua OPEN TO THE PUBLIC Here s what the resulting show html erb looks like Download introduction_to_rails rouge app views reviews show html erb lt hl1 gt Review for lt review restaurant name gt lt h1 gt lt p gt lt b gt Title lt b gt lt review title gt lt p gt lt p gt lt b gt Content lt b gt lt review content gt lt p gt lt link_to Edit edit_review_path review gt lt link_to Back reviews_path gt While we re at it the overall list of reviews should also include restau rant names Download introduction_to_rails rouge app views reviews index html erb lt hl gt Listing reviews lt hl gt lt table gt lt tr gt lt th gt Restaurant lt th gt lt th gt Title lt th gt lt tr gt lt reviews each do review gt lt tr gt lt td gt lt review restaurant name gt lt td gt lt td gt lt review title gt lt
380. ySQL adapter the establish connection part should look like this instead Download databases specific_connect rb ActiveRecord Base establish_connection adapter gt jdbcmysql database gt using_jruby thost gt localhost username gt root password gt This configuration looks more like the regular Ruby version of the same code because it omits the ugly JDBC URL and driver specification It s also possible to fetch your database connection from JNDI You do this by providing a parameter named jndi which has the name of the JNDI object to get the database connection from If you do that you can leave out most of the other parameters Download databases jndi_connect rb ActiveRecord Base establish_connection adapter gt jdbc jndi gt jdbc using_jruby driver gt com mysq jdbc Driver We won t describe in detail all the features of ActiveRecord here there are better places to find that documentation It s worth highlighting some of the main features though so you know what s possible Migrations The original Active Record pattern suggests a structure for your data base How do you create that structure in the first place and how do you modify it as your data model changes This is where the ActiveRe cord library s notion of migrations comes in A migration is a piece of 5 Java Naming and Directory Interface a way for Java services to discover o
381. yield 1 count map n self get_object n end end end begin url jdbc mysq localhost using_jruby conn DriverManager get_connection url root stmt conn create_statement p stmt execute_query SELECT FROM book to_a ensure stmt close rescue nil conn close rescue nil end This code modifies ResultSet to support Ruby s Enumerable behavior sim ply by adding an each method This method is actually quite cute It fetches the column count from the result set metadata and then uses this information to fetch all the column data on every iteration Once we have this method on ResultSet we can use familiar Ruby idioms like to_a on the result of our SELECT The full range of operations are available including map inject and sort Ruby collection In effect we re building our own framework on top of JDBC in just a few lines of code In many cases you don t need anything more than a little Ruby magic sprinkled on top of a Java library like this this copy is P1 0 printing WRAPPING UP lt 164 6 4 Wrapping Up Databases are in many ways a strange aspect of programming Some developers treat them as a low level implementation detail After all our customers don t care that we re using SQL under the hood they care that our programs don t forget their data And yet a typical RDBMS is like a high level programming system in its own right with its own environments tools and
382. you have it one Ruby class compiled to JVM bytecode in a form that s easy to use from Java We re sure you have lots of questions about where to go from here how to use other Java classes implement interfaces and so on In the next section we ll get into several of these details 4 3 The Details Now that you have some simple Ruby code compiled into a Java project let s explore a few things you might do to help this code fit into the broader Java universe Importing Classes If your compiled Ruby code is going to be part of a larger system youll probably want to import other Java classes into your Ruby code To do this you ll use the same java_import syntax from Chapter 2 Driving Java from Ruby on page 31 with a twist You ll need to use a string rather than a Java style package name to refer to the class Original style java_import com example MyClass Compiler style java_import com example MyClass Here s an example of how to apply this technique to the Waveform class Download compiler waveform waveform_with_import rb require java java_import java io PrintStream Report rinting Jan THE DETAILS class Waveform other methods here java_signature void print PrintStream def print stream stream write The RMS is rms end end This new print method can write out the RMS voltage to a standard Java PrintStream Specifying a Package It s standard Java practic
383. zingly we ve been able to redirect Java calls into our waiting Ruby surrogates even though the Java code in question had no knowledge of Ruby Our charge to you is to start testing with JRuby today Scour your Java projects for some class whose test coverage is less than you d like install RSpec or one of its cousins and add one or two simple tests Odds are you ll see enough of a benefit at the code level to wonder what JRuby can do for your project wide test efforts In the next chapter we re going to zoom out from individual unit tests and consider ways to drive an application as a whole from JRuby We ll also see how to fit your JRuby tests into the universe of Java tools and libraries 8 http rubyforge org projects schmock 9 http flexmock rubyforge org Report erratum 9 1 Chapter 9 Over the past several pages we ve tested individual chunks of Ruby and Java code using Ruby s delightful test frameworks But what about applications as a whole Can JRuby be pressed into service for func tional testing That s the question we re going to lead off with First we ll see how JRuby can turn your user stories into live tests Next we ll take on the most popular class of acceptance testing in Ruby web automation Once we ve completed our tour of Automation ville we ll turn back to the Java universe There are a few aspects of integrating Ruby testing tools into Java projects that we should discuss before

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