[webbeans-dev] Re: Redefinition of @New / clarification of injection for non-contextual instances

[Gavin King]

It gets better. If you declare <New/> as the binding for a bean
defined in XML, you can override the injection metadata for
non-contextual instances.

Excellent!

OK, I'm wrong about this solution being non-satisfying. It's
completely satisfying.

On Wed, Jan 14, 2009 at 11:43 PM, Gavin King <gavin at hibernate.org> wrote:
> There's one important thing that is not especially well-defined in the
> spec today and that has been bothering me for a while. It's to do with
> injection into non-contextual bean instances.
>
> There are a couple of cases where the spec supports injection into
> non-contextual bean instances:
>
> * session beans obtained using JNDI lookup or direct injection using @EJB
> * @New
>
> In each of these cases you get an instance of a bean which is *not*
> bound to the scope declared by the bean. However, the spec still
> requires injection into the bean instance.
>
> However, there may be multiple "beans" (i.e. instances of Bean) of the
> given type:
>
> * one defined using only annotations
> * others defined using XML
>
> and each "bean" may have different dependencies defined.
>
> So the question naturally arises: when I obtain this instance from
> JNDI or using @New or @EJB, exactly *which* "bean" is it an instance
> of? i.e. which set of bean metadata should be used?
>
> I've not found any completely satisfying answer to this question - but
> there's only one possibility that is truly well-defined:
>
> * it is the one defined using annotations ... even if that bean has a
> disabled deployment type!
>
> I've been thinking about how best to characterize this in the spec,
> and I think the answer is slightly surprising.
>
> We should say that for each bean type, there is one extra "bean", so
> we now have:
>
> * the one defined using only annotations
> * one that is exactly the same, but with scope @Dependent, binding
> @New and deployment type @Standard
> * the others defined using XML
>
> We can now characterize session beans obtained using JNDI lookup or
> @EJB as instances of the bean with binding @New, removing the
> ambiguity.
>
> This approach lets me eliminate section 3.10 (yay!), since there is no
> longer anything special/magical about @New, and replace it with some
> shorter notes in 3.2/3.3.
>
> Even better, you'll no longer have to use the concrete type of the
> bean when you inject using @New. This is especially useful for session
> beans with no bean class local view.
>
> So this turns out to be simultaneously a simplification, enhancement
> and clarification of the spec, and it's also easier to implement!
>
> Does that make sense to everybody?
>
> Anyway, I guess I will write this up so you guys can see what it looks
> like in the spec.
>
>
> --
> Gavin King
> gavin.king at gmail.com
> http://in.relation.to/Bloggers/Gavin
> http://hibernate.org
> http://seamframework.org
>



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