Warbler. Warbler is a gem that makes a .war file out of a Rails, Merb, or Rack-based application.
The intent is to provide a minimal, flexible, ruby-like way to bundle all your application files for deployment to a Java application server. Warbler provides a sane set of out-of-the box defaults that should allow most Rails applications without external gem dependencies (aside from Rails itself) to assemble and just work. Warbler bundles JRuby and the JRuby-Rack servlet adapter for dispatching requests to your application inside the Java application server, and assembles all JAR files in WARBLER_HOME/lib/*.jar into your application. No external dependencies are downloaded. Nicksieger's warbler at master - GitHub. EclipseShell - Scripting for Eclipse. Alt.lang.jre: Take a shine to JRuby.