I am running a session bean method (method A) inside a transaction, then I call a method (method B) of my delegate (a plain Java Class) and this method calls a method (method C) in another session bean with "supported" transaction attribute.
Does anyone knows if the initial transaction will reach method C?
method A --> method B --> method C (server) (POJO) (server)
Yes, it will since the method B is in the same transaction initiated by method A (logically method A and method B are in the same session). Method C, which has transaction attribute support, will use the same transaction as in method A.
If a call a method in a simple Java class from my Session Bean, this method works as it was a Session Bean business method
Yes, it does. As long as it calls from a session bean with CMT, the container will manage the transaction.
Instead of putting business logic in the bean, you can have dependent classes implementing business logic and delegate request to the dependent classes. One of the benefit you can get is the flexibility. You can config your app to run in ejb container or just pure jvm at run time.