EJB2 interop, how to obtain EntityManager

[triathlon98]

I am currently stuck with having a lot of EJB2 client code and am in the process of migrating my beans to using EJB3 entity beans instead of CMP2.1.

However, I have a problem. How can I obtain the current EntityManager.

If I create new instance through the EntityManagerFactory, then I end up having distinct managers. I have tried looking up with

String enc = org.jboss.ejb3.Container.ENC_CTX_NAME + "/env/" + unit;
return (EntityManager)ctx.lookup(enc);

but this finds nothing. As these are EJB2 beans, I cannot inject the ENtityManager (seems no t to work).

Any clues?

Thanks,
Joachim

[triathlon98]

ok, if you search long enough, you will find the answer, I think I cracked it by using the following code :

 public EntityManager getEntityManager( String unit )
 {
 try
 {
 InitialContext jndi = new InitialContext();
 Object obj = jndi.lookup( "java:managedEntityFactory." + unit );
 jndi.close();
 return ( (ManagedEntityManagerFactory) obj ).getSession();

 }
 catch (Exception e)
 {
 throw new EJBException( "Can't find EntityManager", e );
 }
 }

[donniedarko]

Thank you.

This actually solved my issue with selecting entity managers on the fly described here:

http://www.jboss.org/index.html?module=bb&op=viewtopic&t=65869

I will reference to your solution from that thread.

[bill.burke]

EJB 3 Beta1 should support EJB 2.1 style beans.

[triathlon98]

Bill,

Could you point me in the direction of a manual/article/example which shows how to do that. Don't seem to have found many derails about this yet.

Thanks,
Joachim

[dgreen999]

I'm also interested in seeing some documentation on this topic. Any pointers?
Another issue: is there a way to do this without directly accessing the JBoss APIs?

[dgreen999]

The following appears to work on JBoss 4.0.3RC2

/**
 * @param managerName the name of the EntityManager as specified in the persistence.xml
 */
public EntityManager getEntityManager(String managerName) throws javax.naming.NamingException {
 // TODO: the following code is JBoss-specific.
 EntityManager entityManager;
 InitialContext jndi = new InitialContext();
 try {
 entityManager = (EntityManager) jndi.lookup("java:/EntityManagers/"+managerName);
 } finally {
 jndi.close();
 }
 return entityManager;
 }

The returned entityManager is the same as if it were created via annotations and injection (ie: it's an instance of InjectedEntityManager). The nice thing here is that even though the technique is JBoss-specific, it doesn't use any org.jboss.* packages.