[webbeans-dev] event type with type variable

[David Allen]

On Fri, 2009-07-24 at 17:03 -0400, Dan Allen wrote:
> I'm going to tread carefully when arguing this point because I am far
> from a master at generics. Unfortunately, it seems that the
> non-normative section of the generics documentation is not consistent
> with the generics API. For instance, in the documentation, a type
> parameter is described as a special kind of type variable. But in the
> generics API, they are two separate things (ParameterizedType and
> TypeVariable). But I may be mistaken.
> 
> With that said, the example I gave fails in Web Beans. Let me give a
> full example:
> 
> public class Artist<T> { ... }
> 
> public class Solo { ... }
> 
> public class TuneSelect {
>     @Any Event<Artist<Solo>> soloArtistEvent;
> 
>     public void soloArtistPlaying(Artist<Solo> artist)
>     {
>         soloArtistEvent.fire(artist);
>     }
> }
> 
> Here's the exception Web Beans spits out.
> 
> java.lang.IllegalArgumentException: Event type
> org.jboss.jsr299.tck.tests.event.eventTypes.Artist is not allowed
> because it is a generic
>     at
> org.jboss.webbeans.BeanManagerImpl.fireEvent(BeanManagerImpl.java:798)
>     at org.jboss.webbeans.event.EventImpl.fire(EventImpl.java:76)
> 
> => same result for soloArtistEvent.fire(new Artist<Solo>())
> 
> If you believe that should be valid, then I will simply mark it as
> ri-broken.

This has been fixed.  A really long time ago event objects were supposed
to be simple types.  This just never got changed in the bean manager.

> 
> I see what you are saying though in that what is not allowed is a type
> which is tied to the method parameters, hence acting as a type
> variable.
> 
> -Dan
> 
> On Fri, Jul 24, 2009 at 12:46 PM, Pete Muir <pmuir at redhat.com> wrote:
>         No, the spec prohibits type variables in event objects and
>         event types, it doesn't prohibit type parameters.
>         
>         This isn't legal
>         
>         public class Foo{
>         
>         @Produces <T> Bar make(@Any Event<T> event) {
>         ...
>         
>         }
>         
>         and we do need to error at deployment time for such a
>         declaration. Do we?
>         
>         What you show *is* valid.
>         
>         It's also not valid to actually pass an event object with a
>         type variable, but it's extremely hard to actually find code
>         that will compile and pass the above deployment test, but
>         still do this and do this so I can't find an example right
>         now ;-)
>         
>         
>         
>         
>         On 24 Jul 2009, at 17:28, Dan Allen wrote:
>         
>         
>                 
>                 In several places, the specification reiterates that
>                 an event type may not contain a type variable.
>                 However, it appears that this restriction is only
>                 enforced at runtime when the event object is passed to
>                 either Event#fire() or BeanManager#fireEvent() method.
>                 I would suggest that an validation check be added so
>                 that the container detects an illegal Event definition
>                 at deployment type. Here's an example of an illegal
>                 definition (from my understanding):
>                 
>                 public class VoterRegistration<T> { ... }
>                 
>                 @Any Event<VoterRegistration<Democrat>>
>                 democratRegisteredEvent;
>                 
>                 -Dan
>                 
>                 -- 
>                 Dan Allen
>                 Senior Software Engineer, Red Hat | Author of Seam in
>                 Action
>                 Registered Linux User #231597
>                 
>                 http://mojavelinux.com
>                 http://mojavelinux.com/seaminaction
>                 http://in.relation.to/Bloggers/Dan
>                 
>                 _______________________________________________
>                 webbeans-dev mailing list
>                 webbeans-dev at lists.jboss.org
>                 https://lists.jboss.org/mailman/listinfo/webbeans-dev
>                 
>         
> 
> 
> 
> -- 
> Dan Allen
> Senior Software Engineer, Red Hat | Author of Seam in Action
> Registered Linux User #231597
> 
> http://mojavelinux.com
> http://mojavelinux.com/seaminaction
> http://in.relation.to/Bloggers/Dan
> _______________________________________________
> webbeans-dev mailing list
> webbeans-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/webbeans-dev