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Obtaining EM properties outside a transaction [message #548184]

Tue, 20 July 2010 22:14

Eclipse User

I need to know, for instance, which kind of database my entity manager is referencing (mysql, oracle..).

The code below is an aproach:

Session session = em.getSession();
if (session.getDatasourcePlatform().isOracle()) {
  ....
}

But, I need to put this code inside a method that is not in a transaction context. More precisely, I need to obtain this information inside a EJB method with transaction type supports.

The code above doesn't work outside a transaction context, because the session is null. Is there a way to obtain this information (or other entity manager property) without a transaction? Can I obtain the session without being inside a transaction context?

Thanks. Mauro.

Re: Obtaining EM properties outside a transaction [message #548728 is a reply to message #548184]

Thu, 22 July 2010 14:25

Eclipse User

Same question is posted here:
http://www.eclipse.org/forums/index.php?t=msg&th=172200& amp;start=0&
use getServerSession or getUnitOfWork()

Best Regards,
Chris

Re: Obtaining EM properties outside a transaction [message #548768 is a reply to message #548728]

Thu, 22 July 2010 18:36

Eclipse User

Chris,

Thanks for the answer. But, I don't think that is the same question. Or I didn't get it.
I don't have a trasaction context.
I put in one EJB method (with support annotations) all alternatives, and none of them worked out.

 @TransactionAttribute(TransactionAttributeType.SUPPORTS)  
  public List<AlunoED> lista(AlunoED alunoED) {
    try {
      Session session = JpaHelper.getEntityManager(em).getSession(); // 1
      System.out.println("session = " + session );
    } catch (Exception e) {
      System.out.println("session - exception " + e.getMessage() );
    }
    try {
      Session serverSession = JpaHelper.getEntityManager(em).getServerSession(); // 2
      System.out.println("serverSession = " + serverSession );
    } catch (Exception e) {
      System.out.println("serverSession - exception " +  e.getMessage() );
    }
    try {
      Session unitOfWork = JpaHelper.getEntityManager(em).getUnitOfWork(); // 3
      System.out.println("unitOfWork  = " + unitOfWork );
    } catch (Exception e) {
      System.out.println("unitOfWork - excepption " + e.getMessage());
    }

Calling this method I have the following display on console:

session - exception null
serverSession = null
unitOfWork - excepption null

If I change the transaction type to Required, then the result change:

session = null
serverSession = ServerSession(
	DatabaseAccessor(connected)
	Oracle10Platform)
unitOfWork  = UnitOfWork(
	DatabaseAccessor(connected)
	Oracle10Platform)

But, I don't want to create a transaction context just to obtaing this information in a method that won't update de database.

Re: Obtaining EM properties outside a transaction [message #548967 is a reply to message #548768]

Fri, 23 July 2010 10:46

Eclipse User

Hello Mauro,

I have no idea why you would get an exception 2 out of the 3 times you call JpaHelper.getEntityManager(em).getX() without a transaction. I suspect that there is no delegate entitymanager, that the server is returning a proxy and has not deployed or obtained the underlying EclipseLink entityManager yet when you are calling JpaHelper.getEntityManager(em), which would cause the method to return null. But I have no idea why this wouldn't result in a NPE 3/3 times.

Maybe try a simple operation that the proxy would need to use the EclipseLink em for - something like isOpen or contains on the em before trying to get the sessin. Other than that, you will need to consult with the server docs to see how to get the delegate em (if em.getDelegate() is returning null as I suspect).

Best Regards,
Chris

Re: Obtaining EM properties outside a transaction [message #549044 is a reply to message #548967]

Fri, 23 July 2010 15:53

Eclipse User

Chris

- em.isOpen, em.contains - didn't change anythis.
- getDelegate() - do not return null

  @TransactionAttribute(TransactionAttributeType.SUPPORTS)  
  public List<AlunoED> lista(AlunoED alunoED, PropriedadesLista qp) {
    System.out.println("em is open: " + em.isOpen() );    
    System.out.println("em contains: " + em.contains(alunoED));
    EntityManager emdelegate = (EntityManager) em.getDelegate();
    System.out.println("em delegate: " + emdelegate);
    try {
      Session session = JpaHelper.getEntityManager(emdelegate).getSession(); // 1
      System.out.println("session = " + session );
    } catch (Exception e) {
      System.out.println("session - exception " + e.getMessage() );
    }
    ....

I'll open a call to Oracle. The application server is weblogic 11g.

Thanks.

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