JRuby script in a signed jar OK, let's dive into the world of JRuby a little further, specifically let's touch on the boundary between Java and JRuby again. One excellent way to run JRuby for certain situations is to put the JRuby code (along with some Java code) in a signed, executable jar. A fairly common reason to do this would be the following: you want to run some ruby code (in the JVM) and you want to make sure that no one modifies the contents of the JRuby file (thus you sign the jar). Of course this does not offer you perfect protection, but it adds another layer making it more difficult to subvert your efforts. For the time being, I will assume that you have JDK 1.5 and not JDK 1.6... which means that the scripting framework is not available to you. So, simply include the JRuby jar file in your classpath and jar up the following class along with your ruby files. You should be sure to sign the jar when you create it and you should add pkg.JRubyRunner as your main class so the jar file is executable. Then executing "java -cp jruby.jar -jar MyJar.jar" will run your jruby code AND since the jar file is signed no one will be able to modify your ruby files! (Again, with some effort of course a hacker could modify the ruby file if they had access to the jar.)

package pkg;

import org.jruby.Main;

public class JRubyRunner {
  public static void main(String[] args) throws Exception {
    runJRubyScript("ipc.rb", args);
  }

  public static void runJRubyScript(String name, String... args) {
    // modify the args for jruby
    String[] args2 = new String[2 + args.length];
    if (args.length > 0) {
      System.arraycopy(args, 0, args2, 2, args.length);
    }
    args2[0] = "-e";
    args2[1] = "require '" + name + "'";
    // execute the ruby script
    Main.main(args2);
  }
}

Now, for a few subtle points that you may have missed, especially considering the simplicity of the code. For starters, why you may ask, not just pass in the name of the ruby file? Why use the -e option at all? Well, the reason is because the ruby file is located in the jar file so it is not accessible via java.io.File which JRuby uses to load the file. This makes perfect sense. And since it defeats the purpose to move the ruby file outside of the signed jar, we must find another way to get this to work. You could read in the entire contents of the file from the classpath and pass it into the -e option, but this is ugly and extremely prone to error, so we take advantage of an excellent feature of 'require' in JRuby. Require loads its files from the classpath. This is excellent, because it means that if we require just the file we want to run, it will be loaded from the classpath and and subsequent requires will be loaded from the classpath as well.

Configuring JRuby in IntelliJ IDEA 6.0.5 So you know Java, you've played around with Ruby and now you are interested in trying out JRuby in your favorite IDE (which naturally is IntelliJ IDEA) or maybe you just want to try out Ruby/JRuby... Unfortunately, JetBrains is still a little behind with their Ruby, and especially JRuby, support for IntelliJ. But have no fear, just follow the steps below and you'll be up and running without too much trouble.

[Legal disclaimer: This was tested on Mac OS X with Java 1.5, JRuby 1.0 and IntelliJ 6.0.5, but should work on any Windows or *nix based system with IntelliJ 6.0.x and the JRuby 0.1 plugin.]

[Legal disclaimer: The screen shots in these instructions are not actually perfect or exactly what you will see at all stages of the process, however they should contain all the information required.]

1. Install Ruby Plugin for IntelliJ Instructions (Leaves this page) [Don't look for a JRuby plugin, install the Ruby plugin.]
2. Download and Install JRuby (unzip to the desired installation directory) Instructions (Leaves this page)
3. [UPDATE: I PUT IN A FEATURE REQUEST AND JETBRAINS INCLUDED IT SO NOW THERE IS SUCH A THING AS A JRUBY SDK SO THIS STEP IS NO LONGER REQUIRED! YEAH JETBRAINS!!!!] Create a Ruby link (*nix) or bat file (Windows) [UPDATE: Creating a bat file named ruby.bat does NOT work. IntelliJ looks for ruby.exe which makes this trick more of a pain... On Windows it is probably simpler to create an External Tool for JRuby right now. That way you can right click on a file and execute it and it doesn't require any fancy hacks. Instructions for creating/configuring the "external tool" are below.] that points to the JRuby executable [The IntelliJ plugin requires the executable file be called "ruby" and not "jruby" so we simply trick it by creating a file that points to the real JRuby executable. Hopefully JetBrains will change this for future releases.]
   • *nix soft link: ln -s jruby ruby
4. Create a project with a Ruby module (note: create a Ruby module NOT a JRuby module as you won't find any such thing as a JRuby module. Nor do you need one for that matter, as the Ruby module will do just fine thank you very much. I suppose that JRuby wouldn't be very good if it couldn't just replace Ruby as that is what it is designed to do after all! Well, sort of anyway.)

   
   

5. Point IntelliJ to your JRuby SDK

   
   
   

So now you can execute Ruby files using JRuby as your runtime in IntelliJ. But what if you want to call out to some Java code? In JRuby you have to manage the classpath if you want to call out to java classes. You can do this by setting the $CLASSPATH environment variable or by using the $CLASSPATH global variable. (which is only accessible after you have executed the " require 'java' " statement) Unfortunately, IntelliJ does not set either value when including a Java module. To be fair, the latter case wouldn't really be possible because of the sequencing that is required, but hopefully they do add support so that in the future the $CLASSPATH environment variable is set automatically for you so classpath dependencies can be managed by the IDE just like for other projects/modules.

The EASY CASE (Ruby modules only)

1. Create java_cp file and enter classpath values [NOTE: Classpath values must end with a trailing slash due to the implementation of the java module in JRuby.]

   

2. Include java_cp after java and before including any classes

   

3. Run files by right clicking on the file and choosing Run or by selecting the file and hitting the Run shortcut key sequence.

The HARDER CASE (Ruby modules and Java modules in the same project)

1. Change the ruby project SDK to Java (Otherwise your Ruby module will be fine but your Java modules will not work due to a bug in the Plugin.)

   See, I told you, you get an irrelevant, nasty error message!

2. Create a JRuby External Tool (Carefully note the parameters and working directory used. Notice that I made the working directory the lib directory where I put my source file(s). This screen shot is inconsistent with the other screen shots taken because it came from another project, so just take my word for it. :))

   

3. Run your Ruby files by selecting the file and choosing Tools -> JRuby.

So, there currently is not a perfect solution for running JRuby in IntelliJ IDEA, however these few steps should get you up and running in a minimal amount of time. In the simple case there are only really two steps that are required that wouldn't be present if you were just using the Ruby plugin itself: creating the link to the executable file and managing the classpath manually (in this case via an included file jruby_cp).