Is transactional #observes working for fired events on JBoss AS 7? - events

Question

In order to use events only listened if a transaction succeeds or fails, I'm following the given doc about transactional observers :
http://docs.jboss.org/weld/reference/1.1.0.Final/en-US/html_single/#d0e4075
... but cannot manage to make my code work on JBoss AS7.
Here's my EJB:
#LocalBean
#Stateful
#TransactionAttribute(TransactionAttributeType.NEVER)
public class MyController
{
#Inject
private transient Event<MyEvent> myEventLauncher;
#TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public void save()
{
myEventLauncher.fire(new MyEvent());
}
#AfterCompletion
protected void afterSave(boolean isCommitted)
{
// do stuff
}
}
And here my basic listener:
public class MyHandler
{
protected void listenMyEvent(#Observes(during=TransactionPhase.AFTER_SUCCESS) MyEvent event)
{
// do stuff
}
protected void listenMyEvent2(#Observes(during=TransactionPhase.AFTER_FAILURE) MyEvent event)
{
// do stuff
}
}
I can say I'm in a transaction when the event is fired, because the afterSave method of the EJB is called. Alas, the methods listenMyEvent and listenMyEvent2 are always called both, like if I was not in a transactional context.
I tried the same code on GlassFish 3 and it perfectly works, so I guess there is a problem with JBoss AS 7, but I cannot find any bug report about it.

Answer 1

Well, as my current tests made me think that transactional observers are not working in JBoss AS 7, I managed to do a workaround I gave here for people who are interested.
First, we need qualifier annotations: Immediate, AfterFailure and AfterSuccess.
#Qualifier
#Retention(RetentionPolicy.RUNTIME)
#Target({ ElementType.FIELD, ElementType.PARAMETER })
public #interface AfterFailure
{}
#Qualifier
#Retention(RetentionPolicy.RUNTIME)
#Target({ ElementType.FIELD, ElementType.PARAMETER })
public #interface AfterSuccess
{}
#Qualifier
#Retention(RetentionPolicy.RUNTIME)
#Target({ ElementType.FIELD, ElementType.PARAMETER })
public #interface Immediate
{}
Also, three basic AnnotationLiteral to create in runtime instances of this three annotations.
Then, we need a encapsulator for our true events, that I named SpecialEvent.
public class SpecialEvent
{
private Object event; // the real event you want
public SpecialEvent(Object event)
{
super();
this.event = event;
}
public Object getEvent()
{
return event;
}
}
And at last, an observer for this special event and an interceptor for classes where you want to fire this kind of events (full explanation below).
#RequestScoped
public class SpecialEventObserver
{
#Inject
private Event<Object> anyEventFirer; // firer for real events
private List<Object> events; // queued events
public SpecialEventObserver()
{
events = new ArrayList<Object>();
}
// remove all queued events
public void reset()
{
this.events.clear();
}
public void fireAfterFailureEvents() throws Exception
{
this.fireAllEventsOnce(new AfterFailureLiteral());
}
public void fireAfterSuccessEvents() throws Exception
{
this.fireAllEventsOnce(new AfterSuccessLiteral());
}
protected void listenSpecialEvent(#Observes SpecialEvent specialEvent)
{
Object event = specialEvent.getEvent();
this.events.add(event);
this.fireEvent(event, new ImmediateLiteral());
}
protected void fireAllEventsOnce(Annotation qualifier) throws Exception
{
try
{
for (Object event : this.events)
{
this.fireEvent(event, qualifier);
}
}
catch (Exception e)
{
throw e;
}
finally
{
this.events.clear();
}
}
protected void fireEvent(Object event, Annotation qualifier)
{
Event eventFirer = anyEventFirer.select(event.getClass(), qualifier);
eventFirer.fire(event);
}
}
#Interceptor
#LocalInterception
public class MyInterceptor implements Serializable
{
#Inject
private SpecialEventObserver specialEventObserver;
#AroundInvoke
public Object intercept(InvocationContext ic) throws Exception
{
specialEventObserver.reset();
try
{
// call the real method
Object proceedResult = ic.proceed();
// real method succeeded, fire successful events
specialEventObserver.fireAfterSuccessEvents();
return proceedResult;
}
catch (Exception e)
{
// real method failed, fire failed events
specialEventObserver.fireAfterFailureEvents();
throw e;
}
}
}
The mechanism is quite simple:
When you want to fire an event, fire a SpecialEvent that hold the true event.
The SpecialEventObserver will catch any SpecialEvent and will immediately fire your own event with an Immediate qualifier. It will also queue the events for the after completion part.
At the end of your own method call (ic.proceed in the interceptor), MyInterceptor will ask the SpecialEventObserver either to fire again all events with a AfterFailure qualifier or a AfterSuccess qualifier, depending of the success of your method.
In place of #Observes(during=...), your own observers have to observe events with the right qualifier, like #Observes #Immediate, #Observes #AfterFailure or #Observes #AfterSuccess.
The behavior is not exactly the one that provides the native #Observes(during=...). The after completion part is not based on the transaction state, but on your own method call success:
In JaveEE6, transactional observers on after success or after failure phases must be immediately called if you're not in a transaction, like a IN_PROGRESS would do.
In this workaround, observers on after success or after failure phases will always be called at the end of the method, and only if it succeeded or failed.

Answer 2

This works with version 7.1.0.Final which is supposedly (-> with Jboss you never know) fully Java EE compliant. Also your bean is not thread-safe as it uses list instead of a concurrent queue.

Answer 3

Your observer methods need REQUIRES_NEW, as stated here :
http://www.seamframework.org/Documentation/WhyIsThereNoActiveTransactionInMySFSBTransactionalObserver