Redmine

hello,
I'm a developer from china. I have been using redmine (based on ruby on rails) for a project management application this year. I 'm looking for a open source java version of redmine that can be more easily customized for user needs.
I just find JRedmine on the internet(http://www.nuiton.org/repositories/browse/jredmine/tags), seems like a java version of redmine client only (though not sure what 's the client used for yet).
Since here is the forums with many experts on this field, I wonder if you guys could help me find a java version of redmine, which is open source, with complete functionality of project management as redmine and implemented using java language, if any one know of any such system, could you let me know? We could also coooperate with the development of such open source java system if possible, as java is more familiar relative to ruby currently.

thank you very much!

Xiaochuan Lin