What are some good ways to integrate Ruby into legacy Java  
applications?  I realize
I can execute small Ruby scripts from Java like this:

         Ruby runtime = Ruby.newInstance();
         runtime.evalScriptlet("puts 'Hello from Ruby'");

However, this seems to lend itself only to small snippets of Ruby.    
Often I'm more likely
to have a larger body of Ruby code that includes many files, gem  
dependencies, and
the ability to work with legacy installers.  Is there an easy way to  
accomplish this?