[cdi-dev] Accepting class type for simple (qualifier) annotations in APIs?

[Martin Kouba]

Dne 15.9.2016 v 10:48 Antoine Sabot-Durand napsal(a):
>
>> Le 15 sept. 2016 à 10:26, Martin Kouba <mkouba at redhat.com> a écrit :
>>
>> Dne 15.9.2016 v 10:15 Antoine Sabot-Durand napsal(a):
>>> Just a naive remark regarding Instance of annotations without members. I already used a lambda to have such an instance:
>>>
>>> BeanManager.getBeans(MyBean.class, () -> MyQualifier.class)
>>
>> What is this cryptic unclear lambda thing doing actually? I know it compiles but I don't understand…
>
> It compiles and works every the time I used it. From my understanding it’s a short cut for
>
> BeanManager.getBeans(MyBean.class, new Annotation() {
>     @Override
>     public Class<? extends Annotation> annotationType() {
>         return MyQualifier.class;
>     }
> })
>
> Which by the way also works. From your answer I guess it’s a bad solution ;), but I’d be happy to know why and what is the side effect makes it work.

I don't say it's a bad solution, but it's not obvious and I consider 
similar things a bad practice, especially if we don't understand why it 
works ;-)

>
> Thanks,
>
> Antoine
>
>>
>>>
>>> I’m not sure there are no problem by using this short cut, but it is quite convenient.
>>>
>>> Antoine
>>>
>>>
>>>> Le 12 sept. 2016 à 12:28, arjan tijms <arjan.tijms at gmail.com> a écrit :
>>>>
>>>> Hi,
>>>>
>>>> Wouldn't it be convenient as the CDI API that now requires an Annotation instance in various APIs, would also accept the class type of that Annotation?
>>>>
>>>> E.g. in BeanManager there's this method:
>>>>
>>>> Set<Bean<?>> getBeans(Type beanType, Annotation... qualifiers)
>>>>
>>>> This not rarely requires one to create an AnnotationLiteral, which is not specifically difficult but a tad verbose. For qualifiers that have no (binding) attributes, a simple Class would be much easier to use.
>>>>
>>>> Thoughts?
>>>>
>>>> Kind regards,
>>>> Arjan Tijms
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>>>
>>>
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>>>
>

-- 
Martin Kouba
Software Engineer
Red Hat, Czech Republic