JPA entity manager from Datasource during runtime

Question

I'm wondering if there is possibility to create EntityManager from defined datasource in AS during runtime via JNDI lookup. Imagine that administrator configures a new datasource within the AS (TomEE, JBoss, Glassfish... it could be any JEE6 AS) and I want to use this datasource only by providing JNDI name of this datasource in my application.

String datasourceName = "java:/myDS";
Datasource/Resource datasource = // some JNDI lookup via datasourceName
EntityManager em = // some magic, maybe with EntityManagerFactory

Note that it would be nice to stay in Java EE 6 specification and not use any vendor specific implementation.

Answer 1

It has been almost 3 years, so I suppose there is no easy way to do so. I'm closing this question. If anyone finds solution in the future, you may post answer and I will re-check the correct answer.

Answer 2

I suggest to create two entityManagerFactory object and inject properties using @PersistenceUnit(unitName='') and create entityManager from factory object and use within a transaction context and then clear it.

Class EntityManagerProducer{
@PersistenceUnit(unitName='')
EntityManagerFactory emf1;
@PersistenceUnit(unitName='')
EntityManagerFactory emf2;
 
EntityManager getEm1()
{
return emf1.createEntityManager();

}

EntityManager getEm2()
{
return emf2.createEntityManager();

}
}