Use Your Favorite Ruby Library in Java

For QuickDeck we wanted to support Textile style editing, but we weren't able to find a great Java library to do it. I've been using RedCloth for my Ruby work - why not use that? Along comes Spring's built-in JRuby support to rock my world.
Here's the entirety of the process for integrating:

Add the JRuby jar

We're using Maven 2, so this just means adding a dependency like so:

<dependency>
  <groupId>org.jruby</groupId>
  <artifactId>jruby</artifactId>
  <version>1.0</version>
</dependency>

Define the interface to implement

public interface TextileEngine {
    String textileToHtml(String textile);
}

Create a JRuby script to integrate

This is a little singleton that adapts the RedCloth library to my interface.

require 'redcloth'

class RedClothTextileEngine
  def textileToHtml(textile)
    RedCloth.new(textile).to_html.to_s
  end
end
RedClothTextileEngine.new

Put it in your Spring file

<lang:jruby id="textileEngine" script-interfaces="TextileEngine">
  <lang:inline-script>
require 'redcloth'

class RedClothTextileEngine
  def textileToHtml(textile)
    RedCloth.new(textile).to_html.to_s
  end
end
RedClothTextileEngine.new
  </lang:inline-script>
</lang:jruby>

I decided to inline it because it's so short, you can also do something like this:

<lang:jruby id="textileEngine" script-source="classpath:redcloth_integration.rb" script-interfaces="TextileEngine"/&qt;

Use it!

We're using wicket-spring-annot, so just throw something like this in our Wicket components:

    @SpringBean
    private transient TextileEngine formatter;

And we've got Textile formatting courtesy of RedCloth and JRuby. Snap!

Footnote - the sort of ugly underbelly

The one ugly part of this was that I had to copy the redcloth.rb file into my project. It would have been a lot nicer to do something like this in my ruby script:

require 'rubygems'
gem 'RedCloth'
require 'redcloth'

but I don't want to require a separate JRuby install with rubygems, etc. Feel free to enlighten me on how to do this better!