How to handle Application managed entity manager

[chintan4181 <ch...@gmail.com>]

hi, 

We have requirement in which each business department have it's own
persistence unit. At present we have 2 business unit ( and in future it may
arise). Since we have to support dynamic persistent units defined based on
business department, we have replaced @persistenceContext(unitname="x") with 

EntityManagerFactory factory =
Persistence.createEntityManagerFactory(unitName); and we are getting unit
name from xml file.

this is the case of Application managed entity manager. After replacing
container managed entity manager with application managed we are facing many
issues. 

Here is business scenario, we want to handle with application managed entity
manager. 

1) EJB A initiate em.persist( functionDO) 
2) It extract Obj1 from functionDO and call our em.persist(obj1) 
3) it extract obj2 from functionDO and call our em.persist(obj2) 

Sample reference code would be helpful.

Thanks
unmarshall


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Re: How to handle Application managed entity manager

[Jody Grassel <fy...@gmail.com>]

Hey there.

While it is permitted, using Persistence.createEntityManagerFactory() in a
JEE environment is a somewhat treacherous road to walk, as the application
developer bears the full responsibility of the EMF's lifecycle, including
closing the EMF when it is no longer needed.  Applications that create lots
of EMFs and fail to close() them when they are no longer needed (garbage
collecting does not close EMFs) will often encounter out-of-memory
situations.

If this is a J2EE application, I'd recommend simply adding an injection
entry in ejb-jar.xml:

            <persistence-unit-ref>

<persistence-unit-ref-name>jpa/BusinessUnit1</persistence-unit-ref-name>
                <persistence-unit-name>BusinessUnit1</persistence-unit-name>
            </persistence-unit-ref>

The above is functionally equivalent to adding a @PersistenceUnit annotation
to your EJB/Servlet class definition.

In your application's java code, you can perform a JNDI lookup on the ref
name (java:comp/env/jpa/BusinessUnit1 using the example above) and cache the
EMF in a local variable in your EJB (EMFs are thread safe, so this is okay
to do with SL EJBs and servlets).  This way, your business logic can
determine which EMF it needs to use for the persistence operation by
whichever business unit identifier your application uses, and you still gain
the benefit of the application server managing the life cycle of the EMF.

Pseudocode Example (does not check for errors):

@EJB
public class MyEJB {
   private EntityManagerFactory getEMF(String businessUnitName) throws
Throwable {
        InitialContext ic = new InitialContext();
        return (EntityManagerFactory) ic.lookup("java:comp/env/jpa/" +
businessUnitName);
   }

   public void doSomeJPAWork(String businessUnitName, MyEntity persistMe) {
        EntityManagerFactory emf = getEMF(businessUnitName);
        em = emf.createEntityManager();

        tx.begin();
        em.joinTransaction(); // Necessary for JTA tran, ignore if using a
resource-local PU
        em.persist(persistMe);
        tx.commit();

        em.close();
        // Because this is an application managed emf, you don't have to
emf.close()!
   }
}


On Mon, Sep 26, 2011 at 2:00 PM, chintan4181 <ch...@gmail.com> wrote:

> hi,
>
> We have requirement in which each business department have it's own
> persistence unit. At present we have 2 business unit ( and in future it may
> arise). Since we have to support dynamic persistent units defined based on
> business department, we have replaced @persistenceContext(unitname="x")
> with
>
> EntityManagerFactory factory =
> Persistence.createEntityManagerFactory(unitName); and we are getting unit
> name from xml file.
>
> this is the case of Application managed entity manager. After replacing
> container managed entity manager with application managed we are facing
> many
> issues.
>
> Here is business scenario, we want to handle with application managed
> entity
> manager.
>
> 1) EJB A initiate em.persist( functionDO)
> 2) It extract Obj1 from functionDO and call our em.persist(obj1)
> 3) it extract obj2 from functionDO and call our em.persist(obj2)
>
> Sample reference code would be helpful.
>
> Thanks
> unmarshall
>
>
> --
> View this message in context:
> http://openjpa.208410.n2.nabble.com/How-to-handle-Application-managed-entity-manager-tp6833056p6833056.html
> Sent from the OpenJPA Users mailing list archive at Nabble.com.
>