[cdi-dev] RequestScoped and Injection Points
Pete Muir
pmuir at redhat.com
Thu Sep 8 15:25:38 EDT 2011
As Mark says ;-) But from the way I read your comment, I think you've got @Nonbinding the wrong way up completely.
On 8 Sep 2011, at 14:54, Mark Struberg wrote:
> @Nonbinding is pretty easy to explain:
>
> when comparing Annotations e.g.
>
>
> public Car @Produces @RequestScoped @Status(color="red", quality=3) getCarInfo() { return ...
>
> and the injection point
>
> private @Inject @Status(color="green", quality=3) Car myCar;
>
>
> then all the members of the 2 annotations (color and quality) will be checked on equality!
>
> But if you mark some of your annotations members with @Nonbinding, then they will simply get ignored in the comparison!
> So if you only like to carry payload data, then use @Nonbinding.
>
>
>
> This is not only handy for @Qualifier annotations but also e.g. for Interceptors and Decorators!
>
> It is for example very useful when it comes to InterceptorBindings:
>
> Imagine the following annotation:
>
> @InterceptorBinding ...
>
> public @interface Transactional {
> javax.ejb.TransactionAttributeType transactionAttributeType;
> }
>
>
> And since the transactionAttributeType is NOT annotated @Nonbinding, the following InterceptorBindings are NOT equals!
>
> @Transactional(transactionAttributeType=REQUIRES_NEW)
> @Transactional(transactionAttributeType=NEVER)
>
>
> Which means that you would need to provide 1 interceptor implementation per transactionAttributeType!
>
>
> But if you add @Nonbinding and write
>
> @InterceptorBinding ...
>
> public @interface Transactional {
> @Nonbinding javax.ejb.TransactionAttributeType transactionAttributeType;
> }
>
> , then 1
> @Interceptor
> @Transactional
> public class MyOnlyOneTransInterceptor {...
>
> is perfectly enough.
>
> got me?
>
> LieGrue,
> strub
>
>
>> ________________________________
>> From: John D. Ament <john.d.ament at gmail.com>
>> To: Pete Muir <pmuir at redhat.com>
>> Cc: cdi-dev at lists.jboss.org
>> Sent: Thursday, September 8, 2011 8:21 PM
>> Subject: Re: [cdi-dev] RequestScoped and Injection Points
>>
>>
>> Pete,
>>
>> So, I've always treated Nonbinding as not binding against the parameter, treating separate values as separate qualifiers. When using a producer, you end up needing separate producers for each value that you want to support. This thought is roughly what I was trying to dive through.
>>
>> John
>>
>>
>> On Thu, Sep 8, 2011 at 12:19 PM, Pete Muir <pmuir at redhat.com> wrote:
>>
>> Oh yes, let me redo it ;-)
>>>
>>>
>>> @Retention(RUNTIME)
>>> @interface Foo {
>>>
>>> String bar();
>>>
>>> }
>>>
>>> And use it:
>>>
>>> @RequestScoped
>>> class A {
>>>
>>> /// Illegal
>>> @Inject InjectionPoint ip;
>>>
>>> }
>>>
>>> class B {
>>>
>>> @Inject @Foo(bar="baz") A a;
>>>
>>> }
>>>
>>> class C {
>>>
>>> @Inject @Foo(bar="qux") A a;
>>>
>>>
>>> }
>>>
>>> And then let's say we have:
>>>
>>> @RequestScoped
>>> class D {
>>>
>>> @Inject C c;
>>> @Inject B b;
>>>
>>> }
>>>
>>>
>>> On 8 Sep 2011, at 12:15, John D. Ament wrote:
>>>
>>>> I think something's wrong with your example, but I think I get what you mean.
>>>>
>>>> My point is that if Foo were a qualifier and not just an annotation, should they really be the same injected instance?
>>>
>>> If "bar" was binding, it would be a different instance, if bar was non binding, it would be the same instance.
>>>
>>>
>>>> It seems like @Nonbinding when used in @RequestScoped is irrelevant,
>>>
>>> It's not really relevant or irrelevant, it's just orthogonal. @Nonbinding affects type bean resolution, which is an orthogonal concept to scoping of beans.
>>>
>>> But a non binding attribute is still non binding when used with @RequestScoped.
>>>
>>>
>>>> but i'm not sure the spec makes this clear (though in actuality I'm against that idea that it wouldn't work).
>>>
>>> I think we still have a mismatch in understanding here, as really @Nonbinding has nothing to do with scoping, which is why the spec doesn't call this out.
>>>
>>>
>>>>
>>>> On Thu, Sep 8, 2011 at 11:59 AM, Pete Muir <pmuir at redhat.com> wrote:
>>>> No.
>>>>
>>>> Continuing my example, I introduce some new annotation (not a qualifier):
>>>>
>>>> @Retention(RUNTIME)
>>>> @interface Foo {
>>>>
>>>> String bar();
>>>>
>>>> }
>>>>
>>>> And use it:
>>>>
>>>> @RequestScoped
>>>> class A {
>>>>
>>>> /// Illegal
>>>> @Inject InjectionPoint ip;
>>>>
>>>> }
>>>>
>>>> class B {
>>>>
>>>> @Inject @Bar("baz") A a;
>>>>
>>>> }
>>>>
>>>> class C {
>>>>
>>>> @Inject @Bar("qux") A a;
>>>>
>>>> }
>>>>
>>>> And then let's say we have:
>>>>
>>>> @RequestScoped
>>>> class D {
>>>>
>>>> @Inject C c;
>>>> @Inject B b;
>>>>
>>>> }
>>>>
>>>> The *same* instance of A will be injected into B & C when D is accessed. The injection points allow access to the Annotated, which reflects two different injection points.
>>>>
>>>> Not gonna work ;-)
>>>>
>>>>
>>>> On 8 Sep 2011, at 11:40, John D. Ament wrote:
>>>>
>>>>> Pete, Mark,
>>>>>
>>>>> So I get there is no single injection point, however it should be the case that every injection point is declared the same way, no? E.g. they're the "same" in the sense that the line of code is the same, but different in that they exist in different areas.
>>>>>
>>>>> John
>>>>>
>>>>> On Wed, Sep 7, 2011 at 8:38 AM, Pete Muir <pmuir at redhat.com> wrote:
>>>>> For a request scoped bean there is not a single injection point, like there is for dependent beans. Say I have a request scoped bean, Bean A.
>>>>>
>>>>> I have two other beans, of any scope, Bean B and Bean C.
>>>>>
>>>>> If both beans B and C inject A in the same request, then the injection point for A is both Bean B and Bean C.
>>>>>
>>>>> Furthermore, client proxies mean that bean A is instantiated lazily, to solve the circular injection problem, and so has no knowledge of it's injection point when actually created.
>>>>>
>>>>> On 7 Sep 2011, at 01:10, John D. Ament wrote:
>>>>>
>>>>>> CDI Experts
>>>>>>
>>>>>> Was wondering if you could help me understand rationale. In request scoped objects, when you create a producer method that creates request scoped instances, why is there no access to the underlying injection point?
>>>>>>
>>>>>> Let's say that you have a qualifier with a single String value attribute that is nonbinding; let's say @JmsDestination. You have the following injection points:
>>>>>>
>>>>>> @Inject @JmsDestination("jms/MyQueue") MessageProducer queueProducer;
>>>>>> @Inject @JmsDestination("jms/MyTopic") MessageProducer topicProducer;
>>>>>>
>>>>>> In this case, two distinct MessageProducers should be injected. The CDI container should be able to differentiate the two, since they have different values on the qualifier. However, CDI disallows this since the producer methods used to create them would not have access to the injection point. If a second injection point is found, CDI should return the same instance.
>>>>>>
>>>>>> I hope it doesn't sound like I'm babbling, but I wanted to put the question out there to see if it's something that could be addressed.
>>>>>>
>>>>>> Regards,
>>>>>>
>>>>>> John
>>>>>> _______________________________________________
>>>>>> cdi-dev mailing list
>>>>>> cdi-dev at lists.jboss.org
>>>>>> https://lists.jboss.org/mailman/listinfo/cdi-dev
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
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