[webbeans-dev] Re: @Supports

[Gavin King]

On Sun, Nov 23, 2008 at 7:22 PM, Scott Ferguson <ferg at caucho.com> wrote:

> But the mixin problem (proxy mixin) is different from the JMS problem (tuple
> projection).  So they don't really compete, they are different problems.

Yes, I think I agree with that. In which case I'm thinking that we
should do @Prototype and not @Composes since solving "mixin
inheritance for Java" is not really within the scope of what we should
be trying to do in Web Beans 1.0.

Anyway, I think I can just about implement @Composes as a portable extension ;-)

> But it's not a common problem.  Look at it from the perspective of
> Manager.getInstanceByType.  @Composes doesn't do the right thing for JMS.
>  For JMS, the returned objects need to be the real objects, not a mixin:
>
>  Queue queue = manager.getInstanceByType(Queue.class);
>  QueueSender sender = manager.getInstanceByType(QueueSender.class);
>
> The queue and sender object need to be different, because the JMS provider
> would expect its own Queue, and methods like equals() need to work
> correctly.   Correspondingly,  manager.resolveByType(Queue.class) and
> resolveByType(QueueSender.class) would also return different Bean objects.
>
> But @Composes returns a single instance from getInstanceByType and a single
> Bean from manager.resolveByType:
>
>  Queue queue = manager.getInstanceByType(Queue.class);
>  QueueSender sender = manager.getInstanceByType(QueueSender.class);
>
> For @Composes, the queue and sender are the same object, and the Queue does
> not extend the JMS provider's Queue, it extends QueueEndpoint, which would
> be very confusing or useless to the JMS provider.  For @Composes, the Bean
> object for resolveByType is a single Bean with multiple types, not multiple
> Beans with a single type.
>
> So, JMS needs something more like @Prototype, while a new mixin feature
> could use @Composes.

Good, so that's a good answer to the question I'm asking ;-)

-- 
Gavin King
gavin.king at gmail.com
http://in.relation.to/Bloggers/Gavin
http://hibernate.org
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