You’re riding Ruby on Rails on Google App Engine!
Here’s how to get rolling:
Download and install JRuby
Grab a tarball, and just unpack and run!
jruby -S gem install warbler
Use this sample application as a starting point
You can get it from JRuby-Rack's repository on Github.
Change the application id
Edit appengine-web.xml and replace it in the <application> section.
jruby -S rake appengine:deploy \
Join the JRuby community
Join the mailing lists or visit #jruby on irc.freenode.net to stay on top of the latest developments with Rails on Google App Engine.