Jetty Rails aims to run any Warbler based JRuby on Rails or JRuby Merb applications with Jetty Container, loading configuration from Warbler.
This project is useful for people developing JRuby on Rails (or Merb) applications that can not use mongrel for development. Rails and Merb applications integrated with servlet based applications in the same context would be a reasonable reason.
The project has born from my own needs (read more). I needed to run JForum on the same context of my jruby on rails application. I had also to integrate HttpSessions (avoiding single sign on) and use ServletContext in-memory cache store.