We have some JavaEE5 stateless EJB bean that passes the injected EntityManager to its helpers.

Is this safe? It has worked well until now, but I found out some Oracle document that states its implementation of EntityManager is thread-safe. Now I wonder whether the reason we did not have issues until now, was only because the implementation we were using happened to be thread-safe (we use Oracle).

@Stateless
class SomeBean {
    @PersistenceContext
    private EntityManager em;

    private SomeHelper helper;

    @PostConstruct
    public void init(){
        helper = new SomeHelper(em);
    }

    @Override
    public void business(){
        helper.doSomethingWithEm();
    }

}

Actually it makes sense.. If EntityManager is thread-unsafe, a container would have to do

inercept business()
this.em = newEntityManager();
business();

which will not propagate to its helper classes.

If so, what is the best practice in this kind of a situation? Passing EntityManagerFactory instead of EntityManager?