Allow @ListenerFor annotations in other scenarios that components/renderers

[glassfishrobot]

Long time ago, I sended this mail but forget to create the spec issue.

There are some alternate situations where register listeners using @ListenerFor could be useful. For example, on a managed bean application scope with eager=true and register PostConstructApplicationEvent and PreDestroyApplicationEvent.

I have found these issues on mojarra and myfaces:

http://java.net/jira/browse/JAVASERVERFACES-1948
http://java.net/jira/browse/JAVASERVERFACES-1648

https://issues.apache.org/jira/browse/MYFACES-2509
https://issues.apache.org/jira/browse/MYFACES-3179

The curious thing about it is different people try to use it in different situations, but they found that only works for components and renderers (as designed). It could be good to consider this improvement in future JSF versions.

– ORIGINAL MAIL –
[jsr-314-open] Cannot register listener for PostConstructApplicationEvent and PreDestroyApplicationEvent using @ListenerFor annotation

Hi

This issue is related to

https://issues.apache.org/jira/browse/MYFACES-2509 @ListenerFor not processed for global system events

On JSF 2.0 the following system events were added:

javax.faces.event.PostConstructApplicationEvent
javax.faces.event.PreDestroyApplicationEvent

javax.faces.event.PostConstructCustomScopeEvent
javax.faces.event.PreDestroyCustomScopeEvent

javax.faces.event.PostConstructViewMapEvent
javax.faces.event.PreDestroyViewMapEvent

And the following component system events were added:

javax.faces.event.PostAddToViewEvent
javax.faces.event.PreRemoveFromViewEvent
javax.faces.event.PostRestoreStateEvent

javax.faces.event.PreValidateEvent
javax.faces.event.PostValidateEvent

javax.faces.event.PreRenderComponentEvent
javax.faces.event.PreRenderViewEvent

The javadoc of @ListenerFor annotation is clear to say which classes could be a valid target for this annotation:

"....The default implementation must support attaching this annotation to UIComponent or Renderer classes. In both cases, the
annotation processing described herein must commence during the implementation of any variant of Application.createComponent() and
must complete before the UIComponent instance is returned from createComponent()...."

Long time ago on MYFACES-2509, it was mentioned those classes could not be the only target:

Jan-Kees van Andel

JK>> Hrm, it looks like the JavaDoc can be interpreted in multiple ways.
JK>>
JK>> What I read, is that it should be possible for classes that implement
JK>> SystemEventListener, to listen to SystemEvents.
JK>>
JK>> For example: PostConstructApplicationEvent
JK>>
JK>> The current implementation cannot deal with this event, because it occurs
JK>> before the ApplicationImpl code is invoked (there is no component tree at
JK>> that time). For this reason, we need to check it @startup.
JK>>
JK>> But because its so ambiguous, I suggest to leave it out of the (myfaces core) beta release.

Thinking about how to enhance some myfaces projects and reading some documentation I notice this usage on the book The Complete
Reference JavaServer Faces 2.0 Page 509 (just type on google @ListenerFor PostConstructApplicationEvent and you will find it):

@ListenerFor(systemEventClass = javax.faces.event.PostConstructApplicationEvent.class)
public class TestSystemEventListener implements SystemEventListener {
...
}

The previous example does not work on both myfaces and mojarra, because both implement what @ListenerFor javadoc says. But note this
syntax should be valid on JSF 2.0, at least for PostConstructApplicationEvent and PreDestroyApplicationEvent.

I tried something more elaborated like this:

@ManagedBean(name="myCustomListener", eager=true)
@ApplicationScoped
@ListenersFor({
@ListenerFor(systemEventClass=PostConstructApplicationEvent.class),
@ListenerFor(systemEventClass=PreDestroyApplicationEvent.class)
})
public class SimpleFacesConfigListener implements SystemEventListener
{
...
}

Does not work too, but the fact is that syntax should be valid too. Well, maybe we can use @PostConstruct and @PreDestroy and have the
same effect, but it is worth to mention it.

It could be good to know what do you think about it. I feel inclined to include it in myfaces, but better to ask first.

Anyway, it could be good if you can consider if it is worth or not adding @ListenerFor annotation support for JSF application scope objects and
factories (ex: Application, RenderKit, StateManager, ViewHandler .....). I'm not very sure about it, but better to mention it.

Should I create a spec issue for this one? I think yes.

In another topic, looking for more issues, I notice a side effect testing this example:

org.apache.myfaces.testListenerFor.SimpleFacesConfigListener javax.faces.event.PostConstructApplicationEvent org.apache.myfaces.testListenerFor.SimpleFacesConfigListener javax.faces.event.PreDestroyApplicationEvent

public class SimpleFacesConfigListener implements SystemEventListener
{
...
}

In this case according to both myfaces and mojarra implementation, the object instance that receive PostConstructApplicationEvent is
not the same that receive PreDestroyApplicationEvent, so the listener should be "stateless", but the spec does not warn about this
fact (in theory it should be).

regards,

Leonardo Uribe

Affected Versions

[2.0, 2.1, 2.0 Rev a, 2.1 Rev a]

[glassfishrobot]

Reported by lu4242

[glassfishrobot]

@arjantijms said:
What about @ViewScoped beans being able to register for javax.faces.event.PreRenderViewEvent? (or maybe even create a special shortcut annotation for this: @PreRenderView that can be applied to a method like @PostConstruct etc)

[glassfishrobot]

@edburns said:
Set priority to baseline ahead of JSF 2.3 triage. Priorities will be assigned accurately after this exercise.

[glassfishrobot]

This issue was imported from java.net JIRA JAVASERVERFACES_SPEC_PUBLIC-1020

[glassfishrobot]

Closing this as this issue is migrated to jakartaee/faces#1020