Custom transaction handling

Hello,

I want to use the native API of Google Application Engine Datastore (without JDO, JPA, etc.). What do I have to do to create my own transaction mgmt based on Spring transaction handling using GAE specific transaction objects? Or can you give me a link where I can read about doing custom transaction handling? I would prefere using @transactional.

Current solutions I´ve found are always based on JDO, JPA, etc.

TIA
Harald