[webbeans-dev] event type with type variable

[Pete Muir]

On 24 Jul 2009, at 22:03, 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.

I would advise using the JLS which clearly describes type variables  
and type parameters as two separate things which don't form a parent- 
child structure.

>
> 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.

Right this should pass. Please make sure you also file a WBRI - every  
time you mark something ri-broken, it needs an associated WBRI...

BTW this is quite easy to fix - we need to upgrade events to use the  
type parameter resolution stuff that Takeshi wrote for us.

>
> 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
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>
>
>
> -- 
> 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
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