Awesome. I actually fired up Sinatra on JRuby for a micro-app that needs to talk to some Java stuff last week. All of the existing stuff in Scala was way too heavy for the purpose. (Clojure/compojure has comparable overhead to Sinatra assuming you're familiar with Clojure, but it was untenable in this particular circumstance.)

At least half the magic of Sinatra is that you can write a single Ruby script, exec it and not have to fool around with build/generate/scaffold script or web server configuration to get something useful. It seems like you're pretty close, given that Java has no standard dependency retrieval system.