It's a container managed JTA-Transaction. The transaction isn't created in the code. So it should be created by the containter.
void joinTransaction()
Indicate to the EntityManager that a JTA transaction is active. This method should be called on a JTA application managed EntityManager that was created outside the scope of the active transaction to associate it with the current JTA transaction.
Remko (My website)
SCJP 1.5, SCWCD 1.4, SCDJWS 1.4, SCBCD 1.5, ITIL(Manager), Prince2(Practitioner), Reading/ gaining experience for SCEA,