@Asynchronous CDI Events and an @Observes method in @Named bean

问题

I have CDI Events in place to notify my JSF application of progress from EJB processes. The code works fine when everything is synchronous.

@Stateless
public class MySessionBean implements Serializable {

    @Inject
    @ProcessEvent
    Event<ProcessEvent> processEvent; // Also tried to use BeanManager

    @Asynchronous // This annotation breaks my code
    public void runLongProcess() {
        processEvent.fire(new ProcessEvent());
    }

}

@Named
@ViewScoped
public class ManagedBean implements Serializable {

    @EJB
    MySessionBean sessionBean;

    public void runProcess () {
        sessionBean.runLongProcess();
    }

    @Asynchronous // This annotation doesn't work
    public void onEvent(@Observes @ProcessEvent ProcessEvent event){
        LOGGER.log(Level.INFO, "Event was received"); // Never called
    }
}

If I use an @Asychronous annotation on runLongProcess(), the JSF @Observer method is never called.

How can I achieve this functionality ?

JSF 2.2 Glassfish 3.1 JEE 7 Java 8 Omnifaces 2.3

回答1:

There's not necessarily means of a HTTP request anywhere at that moment and in that thread. Therefore, there's not necessarily a JSF view available/identifiable at that moment (let alone a HTTP request or session).

It'll work in an application scoped bean.

Given that you're using OmniFaces 2.3, it might be worth the effort to take a look at <o:socket> to solve the requirement you had in mind. Its documentation also describes exactly this case and how to solve it properly with help of callbacks (and push the result via a web socket to the view).

@Inject
private SomeService someService;

@Inject @Push
private PushContext someChannel;

public void someAction() {
    someService.someAsyncServiceMethod(entity, message -> someChannel.send(message));
}

@Asynchronous
public void someAsyncServiceMethod(Entity entity, Consumer<Object> callback) {
    // ... (some long process)
    callback.accept(entity.getSomeProperty());
}

来源：https://stackoverflow.com/questions/37117457/asynchronous-cdi-events-and-an-observes-method-in-named-bean

标签

jsf

events

asynchronous

cdi