Hi

i try to use 2 persistence unit in a same Hibernate Session. ..

it is possible?

What is a "persistence unit"?

eh, come on, gonzao, you know it!

In JPA, you define your persistent units in "persistence.xml" like this:


In your entities, you describe per annotation, to which persistent units they belong; i.e:


So, as in this example, I have to 2 persistent units, referring to 2 different databases (or database schemas).

My experience with this situation was:

- The transaction manager of JBoss, where my JPA app is running on, threw an exception complaining that the datasources I am using, that is: the JDBC driver (here: MySQL), is not capable of taking part in a 2 phase commit scenario.

- I had to resort to some code trying to manual emulate a 2PC: which isn't save. This means: I annotated an EJB which handles the other datasource with

Then I could invoke methods on that EJB from a transaction method of the EJB connected to the first datasource.

As I said: this is not save enough. If the inner transaction (created with REQUIRES_NEW) succeeds and commits, and the outer transaction fails, you would have to manually reset the results of the inner transaction; you cannot rollback it anymore.

So, a much better way is to split the application into separate processes with services operating on just one datasource, and then calling a service on the other application which has it's own transaction processing.

Thanks Carlo,

Maybe the question wasn't clear. My doubt or problem is in the jar packaging, because my architecture supports modules, that comes in jars, but the entities of this jars are outside of the principal persistence unit

the only way to resolve es create entries with entities in principal persistence unit.