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Is it possible to distribute/share a persistence unit to multiple EJB modules containing entities?

Posted on 2011-09-27
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Last Modified: 2012-05-12
Hi Experts.

In a J2EE 6 EAR, I would like to know if there is any means to distribute/reuse a persistence unit through multiple EJB modules.

As I understand, the unit seems limited to a single module. But I just want to check with you.
And if it is the case, does anyone have recommandation about how it should be implemented? Should entities always be packed in a single module?

Thanks for any lead.
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Question by:__geof__
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6 Comments
 
LVL 20

Expert Comment

by:a_b
ID: 36813680
Yes it possible. You will need to pass the persistence unit around via a utility EJB.
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LVL 6

Author Comment

by:__geof__
ID: 36813963
Thanks a_b.

If I understand you correctly and take a starting point in an EAR, I must add my utility EJB in the lib?

Is it also possible that Netbeans doesn't recognize this setup?
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LVL 20

Accepted Solution

by:
a_b earned 2000 total points
ID: 36813974
Not necessarily in the lib. What you could do is create one EJB in your ear that has the persistence unit and then pass that ejb to other ejbs to use the persistence unit.
Eg.
@Stateles....
public class EJBUtils
{
      @PersistenceUnit(...)
      EntityManager em;

       Create getters and setters
}

@Stateless
public class EmployeeBean
{

    @EJB
    EJBUtilsLocal ejbUtils;

    //Now via ejbUtils you can get a a hold of the entity manager you created.

}

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LVL 6

Author Comment

by:__geof__
ID: 36814010
Just to be precise, I'm talking about Entity Beans (with annotation mapping to the database).
0
 
LVL 20

Assisted Solution

by:a_b
a_b earned 2000 total points
ID: 36863619
You can do that. Use a common EntityManager and refernece the beans from the stateless session beans.
0
 
LVL 6

Author Comment

by:__geof__
ID: 36889999
OK . Thanks. I'll check it out and come back to you.
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