How can i get the session object if i have the entitymanager

问题

I have

private EntityManager em;

public List getAll(DetachedCriteria detachedCriteria)   {

    return detachedCriteria.getExecutableCriteria( ??? ).list();
}

How can i retrieve the session if am using entitymanager or how can i get the result from my detachedcriteria ?

回答1:

To be totally exhaustive, things are different if you're using a JPA 1.0 or a JPA 2.0 implementation.

JPA 1.0

With JPA 1.0, you'd have to use EntityManager#getDelegate(). But keep in mind that the result of this method is implementation specific i.e. non portable from application server using Hibernate to the other. For example with JBoss you would do:

org.hibernate.Session session = (Session) manager.getDelegate();

But with GlassFish, you'd have to do:

org.hibernate.Session session = ((org.hibernate.ejb.EntityManagerImpl) em.getDelegate()).getSession();

I agree, that's horrible, and the spec is to blame here (not clear enough).

JPA 2.0

With JPA 2.0, there is a new (and much better) EntityManager#unwrap(Class<T>) method that is to be preferred over EntityManager#getDelegate() for new applications.

So with Hibernate as JPA 2.0 implementation (see 3.15. Native Hibernate API), you would do:

Session session = entityManager.unwrap(Session.class);

回答2:

See the section "5.1. Accessing Hibernate APIs from JPA" in the Hibernate ORM User Guide:

Session session = entityManager.unwrap(Session.class);

回答3:

This will explain better.

EntityManager em = new JPAUtil().getEntityManager();
Session session = em.unwrap(Session.class);
Criteria c = session.createCriteria(Name.class);

回答4:

I was working in Wildfly but I was using

org.hibernate.Session session = ((org.hibernate.ejb.EntityManagerImpl) em.getDelegate()).getSession();

and the correct was

org.hibernate.Session session = (Session) manager.getDelegate();

来源：https://stackoverflow.com/questions/4148231/how-can-i-get-the-session-object-if-i-have-the-entitymanager

标签

java

hibernate

jpa

hibernate-entitymanager