[cdi-dev] [JBoss JIRA] (CDI-43) Allow Extensions to specify the annotations that they are interested in

[Jozef Hartinger (JIRA)]

    [ https://issues.jboss.org/browse/CDI-43?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12712652#comment-12712652 ] 

Jozef Hartinger commented on CDI-43:
------------------------------------

I don't think this should be a type-level annotation - I like the original proposal much more. Bootstrap optimization that a container may perform based on this metadata is one of the benefits of this change. In addition, this could also serve as a convenient method of filtering container lifecycle events for extension authors - not unlike how qualifiers can be used to filter normal events. For that, per observer method declarations would be necessary.

{code:JAVA}
public class SeamExtension implements Extension {

   public void registerRestClientInjectionPoints(@Observes @HandlesTypes(RestClient.class) ProcessAnnotatedType<?> type) {
      // TODO register @RestClient injection points
   }

   public void registerExceptionHandlerClasses(@Observes @HandlesTypes(HandlesExceptions.class) ProcessAnnotatedType<?> type) {
      // TODO register exception handlers
   }
}
{code}

It would be guaranteed that if the "registerExceptionHandlerClasses" observer method is called, the annotated type is annotated with the @HandlesException annotation.

Furthermore, if we choose a different name for the annotation than "HandlesTypes", I would suggest to drop the option to use the annotation to specify superclasses and interfaces implemented by the event (since this can already be done by a wildcard in the observer method declaration) and leave only the option of filtering based on annotations.
                
> Allow Extensions to specify the annotations that they are interested in
> -----------------------------------------------------------------------
>
>                 Key: CDI-43
>                 URL: https://issues.jboss.org/browse/CDI-43
>             Project: CDI Specification Issues
>          Issue Type: Feature Request
>          Components: Portable Extensions
>    Affects Versions: 1.0
>            Reporter: Stuart Douglas
>             Fix For: 1.1 (Proposed)
>
>
> Currently portable extensions that wish to look for a specific annotation have to look through all availible classes in the ProcessAnnotatatedType event, which is quite inefficient. It would be good if extensions could do something like:
> public void processAnnotatedType(@Observes @RequireAnnotations({@Unwraps.class}) ProcessAnnotatedType pat) 
> This could allow the container to take advantage of annotation indexing to improve boot time performance, as well as reducing uneeded processing in the observer.

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