CODEWITHSUNDEEP
javaglassfishejbjavabeanscdi
Tasos P.
Tasos P.

Reputation: 4114

Injecting a SessionScoped Stateful bean in EntityListener

I'm trying to implement some sort of auditing in a Java EE JPA (2.0) application on GlassFish 3.

I have added a @EntityListeners annotation on my @MappedSuperclass entity, the listener has the @PrePersist and @PreUpdate annotation on its methods which are invoked happily at runtime.

In these methods, I'm trying to use (@Inject) a @Named, @Stateful, @SessionScoped bean (UserSession) in order to get current user's id. The listener class has no annotations at all.

The problem is that I can't get the UserSession bean injected; I always end up with a null value. To this time, I tried the plain @Inject UserSession us; which always injects a null value.I also tried UserSession us = (UserSession) ctx.lookup("java:global/application/module/UserSession"); which always returns a new object (I verified the constructor call, plus the object is empty).

I'm pretty sure I have missed something very important regarding CDI but I can't figure out what. Could someone please point me to the right direction?

Upvotes: 5

Views: 3772

Answers (3)

reegnz
reegnz

Reputation: 927

To this time, I tried the plain @Inject UserSession us; which always injects a null value.

This is because in JPA 2.0 the classes are not managed by CDI, so @Inject won't work with them. These classes are managed by CDI from JPA 2.1 onward as pointed out by Steve K.

I also tried UserSession us = (UserSession) ctx.lookup("java:global/application/module/UserSession");

You cannot lookup beans instantiated by CDI in JNDI. What you can do however, is look up the CDI BeanManager in JNDI and get your bean from the BeanManager. It is guaranteed by the spec of CDI that you will always find the BeanManager from your application in "java:comp/BeanManager". Here is a simplified example:

InitialContext ctx = new InitialContext();
BeanManager bm = ctx.lookup("java:comp/BeanManager");
Set<Bean<?>> beans = bm.getBeans(UserSession.class);
Bean<?> bean = bm.resolve(beans);
CreationalContext<?> ctx = bm.createCreationalContext(bean);
UserSession us = (UserSession) bm.getReference(bean, UserSession.class, ctx);

That will be the Bean managed by CDI, in case the session scoped UserSession instance.

My answer was based on what was proposed in CDI injection in EntityListeners

Upvotes: 1

Tasos P.
Tasos P.

Reputation: 4114

I eventually found a workaround, which allows me to get a reference of the @Stateful bean:

I created a @Named @Singleton @Startup bean SessionController which holds a local HashMap<String, UserSession> sessionMap with the references of my @Stateful beans:

@Named
@Singleton
@Startup
@ConcurrencyManagement(ConcurrencyManagementType.CONTAINER)
public class SessionController {

private HashMap<String, UserSession> sessionMap;

@PostConstruct
void init() {
    sessionMap = new HashMap<String, UserSession>();
}

@PreDestroy
void terminate() {
    for (UserSession us : sessionMap.values()) {
        us.logoutCleanUp(); //This is annotated as @Remove
    }
    sessionMap.clear();
}

public void addSession(String sessionId, UserSession us) {
    sessionMap.put(sessionId, us);
    System.out.println("New Session added: " + sessionId);
}

public UserSession getCurrentUserSession() {
    FacesContext context = FacesContext.getCurrentInstance();
    String sessionId = ((HttpSession) context.getExternalContext().getSession(false)).getId();
    return sessionMap.get(sessionId);
}

}

I add the references from within each bean's @PostConstruct method:

public class UserSession implements Serializable {
@Inject SessionController sc;
...
    @PostConstruct
    void init() {
    FacesContext context = FacesContext.getCurrentInstance();
    String sessionId = ((HttpSession) context.getExternalContext().getSession(true)).getId();
    sc.addSession(sessionId, this);
}

Notice the .getSession(true) which is required since the Session might not be created yet. Also notice that this is safely passed since the @PostConstruct is not the constructor...

After all these, I can get the reference in my EntityListener (and any other place) like this:

SessionController sc = (SessionController) new InitialContext().lookup("java:module/SessionController");
    UserSession us = sc.getCurrentUserSession();

or like this in CDI beans

@Inject SessionController sc;

The only drawback I see is that this approach works well only for web applications (where FacesContext context = FacesContext.getCurrentInstance() is meaningful). Some of my beans (and finally my EntityListeners) are also exposed via @javax.jws.WebService as @Stateless beans. In this context (actually: absence of), my Singleton wouldn't work (haven't tested yet) since there is no sessionId of any kind (no session at all to be exact). I will have to use a workaround for this, possibly using SessionContext of the bean or inventing a usable sessionId of some sort. I will post back if I create something usable...

Upvotes: 1

Steve K
Steve K

Reputation: 19586

EntityListners do not support CDI, at least in JPA 2.0. It's apparently on the list of things new in JPA 2.1

I was also surprised when I ran across this.

Upvotes: 2

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