Recently, NetBeans Ruby Pack has been released, so I tried it immediately. It's very sweat and exciting except one problem. How can I set a classpath to a jdbc diver jar archive? I googled again and again putting various key words in the box, which ended up vain efforts. Instead keep searching, I looked carefully each directory related to NetBeans because JUnit tests seem to work in Ruby on Rails project on NetBeans as in the demo video. Class names of JUnit don't start with java or javax, but JUnit classes seem to be available in Ruby project. I figured out. Jar archives used in Ruby and Ruby on Rails projects exist in the directory /home/username/.netbeans/dev/jruby-0.9.2/lib. When I made a link to derby.jar in that directory, I could get my JRuby code work successfully.
Released Ruby Pack is the very first version and might have bugs and lack of convenient features. By the time those would be fixed and improved, I will avoid the jar-archive-setting problem by making links to necessary jar archives.