Stateful session bean forgets values

Question

With Java EE I need to use a stateful session Bean.

@Stateful
@TransactionManagement(TransactionManagementType.BEAN)
public class FacadeExercice extends AbstractFacade<EntityBeanExercice>
  implements IFacadeExercice {

@PersistenceContext(unitName = "GestionCours-ejbPU")
private EntityManager em;
@Resource
private UserTransaction transaction;
private int lastChange;
private int connections;

[...]

@Override
public EntityBeanExercice find(Object id) {
    EntityBeanExercice ex = null;
    connections += 5;
    try {
        transaction.begin();
        ex = super.find(id);
        lastChange = ex.getLastChange();
        transaction.commit();
    } catch (Exception ex1) {
        Logger.getLogger(FacadeExercice.class.getName()).log(
          Level.SEVERE, null, ex1);
    }
    return ex;
}
}

But every time I enter in my bean, the connections variable is set to 0.

I have no Idea where I can search a solution.

score 2 · Accepted Answer · answered Aug 03 '13 at 19:40

This problem can arise in these situations:

The lifetime of a SFSB is connected to the lifetime of its client.

Your SFSB works fine, if you have a command line client for example. When the command line application is terminated, the SFSB is removed as well.

If the SFSB is used by a JSP/servlet for example, it's lifetime ends, when the HTTP request is completed. If it is to survive the HTTP request, you have to put it's handle in the HTTP session: After you have got an instance from a JNDI lookup, you should put that instance as an attribute in the HttpSession. The next HTTP request to use this SFSB must get the handle from the HttpSession.

Each JNDI lookup returns a new instance

A quote from EJB 3.1, 4.6 Stateful Session Bean State Diagram

When a stateful session bean is looked up or otherwise obtained through the explicit JNDI lookup mechanisms, the container must provide a new stateful session bean instance, as required by the Java EE specification (Section “Java Naming and Directory Interface (JNDI) Naming Context” [12]).

So you should not lookup the SFSB more than one time.

Stateful session bean forgets values

1 Answers1