Question

I have a doubt a long time and never find the answer, so I appreciate any king of help or explanation… maybe it´s is just a conceptual mistake…

I have an environment where I use CMT and Hibernate. I can inject the EntityManager as a resource on my EJB without any problem. But I couldn´t make it inject direct in my DAOs, since I instantiate it with a traditional factory pattern….

But my question is: I need to use the EntityManager, but don´t want to pass it all the way down through my layers! Must have another way and I´m probably not seeing the solution…

Can I do some king of context lookup for this EntityManager? Or any other more elegant solution?

I made my own solution, but its kind of crap lol… don´t worth a discution…

Thanks for any help and sorry for any english mistake, it´s not my native language.

Answer 1

Even following the JBNizet sugestion, I still curious to know how to get the EntityManager and I found this answer in how to lookup for the EntityManager on J2EE/EJB environment.

First, you need to put a @PersistentContext on the class scope of your EJB to set a def for later lookup and define the “name” attribute. Like:

@PersistenceContext(
name="myEntityManagerJNDIName",
unitName=InventoryManagement  // defined in a persistence.xml file
)
@Stateless
public class InventoryManagerBean implements InventoryManager { ... }

Then you can lookup for your EntityManager with a code like this:

...
// obtain the initial JNDI context
Context initCtx = new InitialContext();
// perform JNDI lookup to obtain container-managed entity manager
javax.persistence.EntityManager entityManager = (javax.persistence.EntityManager) 
   initCtx.lookup("java:comp/env/myEntityManagerJNDIName");
...

That is the way I found to get the EntityManager without injections.