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About Question enthuware.oce-jpad.v6.2.518 :
Posted: Sun Sep 02, 2012 8:48 am
by cosminvacaroiu
Isn't a
required here ? otherwise the persist will do nothing
Re: About Question enthuware.oce-jpad.v6.2.518 :
Posted: Sun Sep 09, 2012 3:19 pm
by admin
No, it is not required here because a new transaction is being created in the same code. joinTransaction is required when the transaction is created else where.
HTH,
Paul.
Re: About Question enthuware.oce-jpad.v6.2.518 :
Posted: Sat Aug 12, 2017 5:08 pm
by himaiMinh
I have the same question too. The entity manager is not created before em.getTransaction().begin which creates the transaction.
Why we don't need to call em.joinTransaction?
I assume the code is like this:
Code: Select all
EntityManagerFactory emf = Persistence.createEntityManagerFactory("aPU");
EntityManager em = emf.createEntityManager();
//This persistence context is created when the em is created.
// It is created outside the new transaction
//The new transaction is created and begin after the em is created.
em.getTransaction().begin();
The JPA Pro says "If the persistence context was created earlier(outside of a transaction or in a transaction that has since ended), the persistence context can be manually synchronized with the transaction by calling joinTransaction() on the EntityManager interface."
I guess the above statement is only applicable to the application managed entity manager used with JTA.
For example:
Code: Select all
//In a stateful bean
@PersistenceContext(unitName="aPU")
EntityManagerFactory emf;
EntityManager em;
public void init(){
emf = Persistence.createEntityManagerFactory("aPU");
em = emf.createEntityManager();
}
public void add(....){
em.joinTranscation();
//anEntity is an entity
em.persist(anEntity);
}