Question

I am using JBoss 7 with the default Hibernate JPA engine in an EJB3 / JSF project.

The javadoc on EntityManager::getDelegate reads: “Return the underlying provider object for the EntityManager, if available.”.

Out of curiosity I tried the following code:

@Stateless
public class AFacade {
    @PersistenceContext(unitName="foo")
    EntityManager em;

    public List<A> findAll() {
         l.info("underlying entity manager is: "+em.getDelegate().getClass().getSimpleName());
         ...
    }

The output however indicates the classname as: org.hibernate.internal.SessionImpl which, according to hibernate documentation is a Session implementation.

What am I missing here ?

Answer 1

JPA is just a specification for ORM; there are some implementations for this specification/API the most known being Hibernate, EclipseLink, OpenJPA.

This means that the EntityManager is just an adapter to a class from the implementation library. In your case it is org.hibernate.internal.SessionImpl since you use Hibernate as a JPA implementation – this is the class that manages the code you give to the EntityManager.