An example program to bundle JRuby up in a Maven project using mkristian's [jruby-maven-plugins][2]. To use simply
mvn install
and then go to your target folder and run it:
java -jar ruby-jar-it-with-dependencies-and-gems.jar
This is simply a reference point for trying to create your own. There are obvious use-cases for this kind of thing, such as a hybrid Java/Ruby project, and if you're comfortable using Maven as your build system, you might want to go with this approach to create a runnable .jar.
[2]: