[webbeans-dev] producer method trumps raw dependent type?

[Dan Allen]

Okay, so there is an explicit step that must be taken for a producer method
to win over a @Current bean (does not have additional bindings) of that
type. I suspect in most cases developers will choose to use the binding type
since that is the type-safe approach.

The designation of the alternative class in beans.xml makes all producer
methods in that class have a higher precedence than any @Current bean of
that type, correct? Is it also possible to specify a single method in
beans.xml? There is alluded to in the Policy section, but no examples to
support it.

Btw, I think this would be a lot clearer if it was explicitly stated in the
spec how a producer method relates to a @Current bean of that type. I guess
you could say it can be implied, but the first time someone goes to create a
producer method, I can see them not realizing that they have to take an
extra step to make it the preferred source.

-Dan

On Wed, Jul 22, 2009 at 7:13 AM, Pete Muir <pmuir at redhat.com> wrote:

>
> On 22 Jul 2009, at 03:18, Dan Allen wrote:
>
>  After the recent revisions of the JSR-299 spec, I'm finding that I'm a tad
>> confused about the bean selection algorithm when a producer method exists.
>>
>> Consider the following:
>>
>> class PotatoChip {
>> }
>>
>> class SnackFactory() {
>>    public @Produces PotatoChip createPotatoChip() {
>>        return new PotatoChip();
>>    }
>> }
>>
>> 1) Does the produced PotatoChip take precedence over the raw dependent
>> type when being selected for injection?
>>
>
> No.
>
>
>> 2) How do I get the Bean<PotatoChip> that represents the producer method?
>>
>> BeanManager#getBeans(PotatoChip.class) returns two beans that are
>> indistinguishable from the public API.
>>
>
> either:
>
> @Alternative
> class SnackFactory() {
>    public @Produces PotatoChip createPotatoChip() {
>        return new PotatoChip();
>    }
> }
>
> <beans>
>   <alternatives>
>      <alternative>SnackFactory</alternative>
>   </alternatives>
> </beans>
>
> or
>
> class SnackFactory() {
>    public @Produces @Snack PotatoChip createPotatoChip() {
>        return new PotatoChip();
>    }
> }
>
> BeanManager.getBeans(PotatoChip.class, new AnnotationLiteral<Snack>() {});
>
> where @Snack is a binding type
>
>
>> 3) What if the producer method is @RequestScoped? How do I get the
>> request-scoped produce instead of the dependent bean?
>>
>>      Bean<PotatoChip> potatoChipBean = null;
>>      for (Bean<PotatoChip> candidate : getBeans(PotatoChip.class))
>>      {
>>         if (candidate.getScopeType().equals(RequestScoped.class))
>>         {
>>            potatoChipBean = candidate;
>>            break;
>>         }
>>      }
>>
>> Sorry if this sounds like a dumb question. The spec has changed a lot and
>> my memory is getting mixed in with the current set of facts.
>>
>
> As above.
>
> It's possible the RI doesn't actually reflect this behavior atm - if you
> have a problem, make sure there is a test, then change the RI or file a
> WBRI.
>



-- 
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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