Java for a Ruby/Rails user

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