Injecting EntityManager into EntityListener

[socotech]

I have created a listener to audit entity objects as they are saved and updated:

@EntityListeners(value = {MyEntityListener.class})

...

public class MyEntityListener {
  private EntityManager entityManager;
  @PersistenceContext
  public void setEntityManager(EntityManager em) {
    this.entityManager = em;
  }
  @PrePersist
  public void auditInsert(Object o) {
    // use this.entityManager here
  }
  @PreUpdate
  public void auditUpdate(Object o) {
    // use this.entityManager here
  }
}

So far, everything I've done to inject the EntityManager has failed because entityManager remains null. Is there a way to do this? Thanks.

[michaelre]

EntityListeners are instanciated by JPA, so Spring does not have an opportunityto inject EntityManager. I would reconsider the use of an EntityManager from within an EntityListener, but you could try a ThreadLocal if you really need to make it happen.

[rubens]

Here is how to fix the EntityManager NullPointerException. Add the following line to your applicationContext.xml file:

<context:annotation-config />

[J Ball]

Here is how to fix the EntityManager NullPointerException. Add the following line to your applicationContext.xml file:

<context:annotation-config />

This doesn't appear to work for me, should it?

[CharlF]

Hi All,

Im also having the same problem, and I have the "<context:annotation-config />" in my configuration.
I have the @Repository Annotation on the class, The @Transactional on the method and the @PersistenceContect on the setEntityManager method. but my EM still stays null.

PS. Im trying to get this to work within an EJB environment, not a webapp / MVC environment

any ideas?

[chowdahed]

I'm still new to the JPA thing, but it seems like a deficiency in the JPA spec if the EntityManager is not accessible from within the @Pre* and @Post* methods. Without access to the EM you are pretty much limited to operating on simple properties. If I can't access the EM, then I'm unable to connect related entities to the open session. In my application, the currentUser is a persistent entity. When I try to set the createdBy property in the @PrePersist method, I get complaints about the user entity being detached when the persist() executes.

As an alternative to the ThreadLocal<EntityManager> approach, there is the the opportunity to do pre- and post-processing in the DAO (@Repository) class. Unfortunately, the DAO instances won't get notified of cascaded EM persistence operations like the listeners do.