[Cafesolo]

I'd recommend Objectify instead of JDO.

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.

[adidum]

Believe it or not, but I lived without phone and TV for a few years now, it's great :) I'm giving Google AppEngine a serious try. Otherwise I'll have to look for a Java Web framework, the problem is that there are too many out there. thanks for the advice!