用CDI注入PersistenceContext

持久性上下文和CDI的最佳实践是使它们成为CDI bean以避免此类问题。

public class MyProducers {    @Produces    @PersistenceContext(unitName = "MyPersistenceUnit")    private EntityManager em;}

之后，您将能够以

EntityManager

@Statelesspublic StatelessSessionBean implements StatelessSessionBeanLocal {    @Inject    private EntityManager em;    @Override    public Collection<MyObject> getAllObjects(){        CriteriaBuilder cb = em.getCriteriaBuilder();        CriteriqQuery<MyObject> query = cb.createQuery(MyObject.class);        query.from(MyObject);        return em.createQuery(query).getResultList();    }}

这样，您就可以毫无问题地装饰CDI bean。

如果您有多个

EntityManagers