Using jRuby from Netbeans

Netbeans is a great development platform which supports Ruby and jRuby. In this post, I have collected together the steps I needed to write and run a jRuby script with a library file, such as Weka or my own jChrest.

First, you must download and install the Netbeans platform. ( I started by downloading the version for Java SE alone.)

Second, you must add the plugin to use Ruby programs. To do this start up Netbeans, and select the 'plugins' option on the 'Tools' menu. Under the tab for 'Available plugins', select the 'Ruby' plugin and install it. (You may not need this step, if you downloaded a version with Ruby included in the previous step.)

Third, download and install jRuby. You need to download and unpack one of the 'binary' distributions. Take note of the 'bin' directory, as you need to know this to tell Netbeans about your jRuby distribution.

Fourth, start up Netbeans and create a new ruby project.

After clicking 'next' you need to specify the Ruby platform you want to use.

The first time we do this, we must tell Netbeans about our new jRuby installation, so click on 'Manage...' and select the 'jruby' executable in the 'bin' directory you installed in step 3. Once you've done this, Netbeans will remember your jruby installation for future projects.

Now, you can create some ruby code and click on 'Run Main Project' to see the output in the 'Output window'. Two things may need changing. First, to set a project to be the 'Main' project, the one which is run when you click the green triangle, you need to right click on the name of the project and select 'Set as Main Project'. Second, you may need to change the ruby platform or version. Again, right click on the name of the project and select 'Properties'. Click on the 'Run' option on the left hand side and you can change the Ruby Platform in the choice box, and add options to the interpreter. In the example below, you can see I have made jRuby use 1.9 mode:

Accessing Java Libraries

The final step in setting up the environment is to include a Java library within the project. For example, to work with Weka, you need to access the file weka.jar. To do this within Netbeans, go to the 'Java' option in the Properties dialog box shown above. Select 'Add JAR/Folder' and add the jar file to the classpath for this project. That's all there is to it. The only change I needed to make to my scripts was to remove the line 'require "weka"'; this is taken care of by adding the jar file to the project.