How to deal with discarded Stateful Session bean

Question

Now and then, an operation in my stateful EJB (3.0) throws an SQLException (timeout expired). The method in which it happens:

@PersistenceContext(unitName = "MYPU")
EntityManager entityManager;

List<Message> list;

public List<Message> newSearch() {
    // do some unsignificant things
    loadFirstPage();
}

@TransactionAttribute(TransactionAttributeType.REQUIRED)
public List<Message> loadFirstPage() {
    CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
    cq.select(cq.from(entityClass));
    list = getEntityManager().createQuery(cq).getResultList();
}

This SFSB has been injected in another class:

private MyBean myBean;
@EJB(name = "messageloaderbean")
public void setMyBean(MyBean myBean) {
    this.myBean = myBean;
}

And then its reference passed as parameter in the calling class:

public class Controller{
    private MyBean myBean;

    public Controller(MyBean myBean){
        this.myBean = myBean;
    }
    public void methodThatCallsMyBean(){
        this.myBean.newSearch();
    }
}

What happens now if a runtime exception is thrown (like a SQLException), as I'm using CMT and according to the EJB specification, is that the container first rollbacks the transaction, then discards the EJB. Then, if I want to use again this EJB after its discarding, I get a javax.ejb.NoSuchEJBException: Bean has been deleted.

That makes sense as the bean has been discarded, but how can I get a reference to a fresh new stateful bean?

Should I instead catch the exception in my SFSB and avoid this discarding? What with the state of the transaction if I catch the exception? Do I have to do some manual rollback?

Thanks.

Answer 1

but how can I get a reference to a fresh new stateful bean?

The container injects the proxy at the begining of the bean's life cycle, thus in this case every new staless bean instance will inject the statefull reference only once. An alternative could be get the reference through JNDI lookup but this will be more cumbersome.

Should I instead catch the exception in my SFSB and avoid this discarding?

Yes, I think this is the best solution.

Do I have to do some manual rollback?

Yes. When the Container intercepts a RuntimeException it marks the Transaction for rollback. I you need keep this behavior the current transaction has to be manually marked. There are a couple of alternatives:

a) Throw an Application Exception and to annotate it with @AnnotationException(rollback=true). In this case the container will mark the transaction for rollback without discard the bean instance.

b) Mark the transaction through the SessionContext.setRollbackOnly() method.

//inject a SessionConetext instance
@Resource
SessionContext session;

try {
    //your code goes here
} catch (RuntimeException e) 
//log the error
    session.setRollbackOnly();
{