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

[Gavin King]

OK, here's a writeup.

Please look at sections 3.2.5, 3.3.6 and 5.14. This is a low-impact change.

On Wed, Jan 14, 2009 at 11:46 PM, Gavin King <gavin at hibernate.org> wrote:
> 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
>



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