使用CDI注入PersistenceContext

Question

目前,我正在使用PersistenceContext来注入EntityManager.EM完美注入.

@Stateless
public StatelessSessionBean implements StatelessSessionBeanLocal {

    @PersistenceContext(unitName = "MyPersistenceUnit")
    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();
    }
}

现在我尝试装饰豆子,突然间em没有被注射.我得到一个NullPointerException.

@Decorator
public StatelessSessionBeanDecorator implements StatelessSessionBeanLocal {

    @Inject
    @Delegate
    @Any
    StatelessSessionBeanLocal sb

    @Override
    public Collection<MyObject> getAllObjects(){
        System.out.println("Decorated method!");
        return sb.getAllObjects();
    }
}

我知道EJB和CDI是两个完全不同的管理器,所以那个人不了解另一个.我期望@PersistenceContext是一个EJB注入点,而@Inject是一个CDI注入点.我该怎么做才能解决这个问题并让EntityManager按照它应该注入？

Answer 1

持久化上下文和CDI的最佳实践是使它们成为CDI bean以避免这类问题.

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

之后,您将能够以EntityManagerCDI方式注入.拿你的EJB它将是:

@Stateless
public 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,则可以使用CDI限定符来区分它们