Here is a Rack app that does a Twitter Search, and parses the result with json-jruby:
The “json-jruby” gem requires that you are running Java 1.6 locally. If this is a problem, you can instead use json_pure.
When using gems with Java extensions, appengine-tools drops the appropriate jars into WEB-INF/lib for you.
find .gems -name "*.jar" .gems/bundler_gems/jruby/1.8/gems/json-jruby-1.2.0-universal-java-1.6/lib/json/ext/generator.jar .gems/bundler_gems/jruby/1.8/gems/json-jruby-1.2.0-universal-java-1.6/lib/json/ext/parser.jar