I'd recommend Objectify instead of JDO. http://code.google.com/p/objectify-appengine/ http://code.google.com/p/objectify-appengine/ The reason why Google chos

I'd recommend Objectify instead of JDO. http://code.google.com/p/objectify-appengine/ http://code.google.com/p/objectify-appengine/ The reason why Google chose JDO as the default interface to the AppEngine's datastore instead of JPA is because the datastore is not really a relational database and JDO is much better suited for non-relational backends. However, there's a lot of stuff in JDO that you will never use in an AppEngine application. Objectify is a thin wrapper around the low-level datastore API. It's a pleasure to work with and it will save you a lot of time.