Why not use JRuby on Rails? Leverage your existing skills. You'll probably also benefit from the lack of database because ActiveRecord is the least flaky component in the Rails stack running on JRuby today.
http://www.headius.com/jrubywiki/index.php/JRuby_on_Rails http://www.headius.com/jrubywiki/index.php/Rails_Integration
/Nick