Google Web Toolkit（GWT）+ Google App Engine（GAE）+独立数据持久性

I would like to develop a web-app requiring data persistence using GWT and GAE. As I understand it, my only (or at least by far the most convenient) option for data persistence is GAE's Datastore, using JDO or JPA annotated objects. I would also like to be able to send my objects back and forth client-server using GWT Remote Procedure Calls (RPC), therefore my objects must be able to "detach". However, GWT RPC serialization cannot handle detached JDO/JPA objects and it doesn't appear as though it will in the near future.I would like to develop a web-app requiring dat