[webbeans-dev] event type with type variable

[Dan Allen]

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.

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
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