The warning is fine, it just informs you EJB post-activate and pre-pasivate is not supported,
but in GAE you don't have EJBs anyway.
If it works, you should be fine.
I've been playing with GAE + CDI / Weld a while back:
It's undocumented unfortunately, but a few, imo :-), good ideas are there,
on how to bridge the GAE + JEE.
This slides describe some of the problems and solutions addressed in CapeDwarf Green: