I'm preparing to SCBCD exam and I have problems with understanding various types of Entity Managers.
I know that Application Managed EM can be JTA or ResourceLocal, but what about Transaction Management Demarcation(bean-managed transaction demarcation,or container-managed transaction demarcation) for this type of EM?
It is possible to be a Resource Local EM with Bean Managed Transactions Demarcation? If yes, how can I mark transaction for rollback(I could use: - UserTransaction.rollback(), UserTransaction.setRollbackOnly(), EntityTransaction.rollback(),EntityTransaction.setRollbackOnly())?
Yes, you can use an Resource Local Entity Manager with BMT demarcation. BMT is a different demarcation of a JTA transaction, in my examples codes I can't use EntityManager.joinTransaction() for join the Application Manager-Resource Local Entity Manager transaction to the current JTA. I don't know why, but in my examples when I use EntityManager.joinTransaction with Resource Local I get a exception. Maybe somebody can help us.
Persistence specification 5.5.2 Resource Local Entity Managers:
An entity manager whose transactions are controlled by the application through the EntityTransaction API is a resource-local entity manager. A resource-local entity manager transaction is mapped
to a resource transaction over the resource by the persistence provider. Resource-local entity managers
may use server or local resources to connect to the database and are unaware of the presence of JTA
transactions that may or may not be active
I understand that the JTA transaction, in this case with BMT demarcation, is unaware by the EntityManager and due to is a Resource Local it can't join the Resource transaction with the current JTA, for that I see this configuration like independent transactions, once JTA BMT transaction and other a Resource Local Transaction. If you want to rollback the JTA transaction you must use UserTransaction.setRollbackOnly(), if you want to rollback the entity operations you must use EntityTransaction.setRollbackOnly().