[cdi-dev] Should javax.enterprise.inject.Produces be inherited?
Emily Jiang
EMIJIANG at uk.ibm.com
Tue Sep 13 04:37:08 EDT 2016
First of all, the subject line suggests the produces should be inherited
under all conditions. Anyway, after your explanation, I think this
suggestion contradicts with spec and breaks backward compatibility. In the
cdi 1.2/cdi 2.0 spec,
The only way one bean can completely override a second bean at all
injection points is if it implements all the bean types and declares all
the qualifiers of the second bean. However, if the second bean declares a
producer method or observer method, then even this is not enough to ensure
that the second bean is never called!
To help prevent developer error, the first bean may:
directly extend the bean class of the second bean, or
directly override the producer method, in the case that the second bean is
a producer method, and then
explicitly declare that it specializes the second bean.
After this suggestion, the above sentence is not true any more.
Many thanks,
Emily
===========================
Emily Jiang
WebSphere Application Server, CDI Development Lead
MP 211, DE3A20, Winchester, Hampshire, England, SO21 2JN
Phone: +44 (0)1962 816278 Internal: 246278
Email: emijiang at uk.ibm.com
Lotus Notes: Emily Jiang/UK/IBM at IBMGB
From: John Ament <john.ament at spartasystems.com>
To: Matej Novotny <manovotn at redhat.com>, Mark Struberg
<struberg at yahoo.de>
Cc: Emily Jiang/UK/IBM at IBMGB, cdi-dev <cdi-dev at lists.jboss.org>
Date: 12/09/2016 13:31
Subject: Re: [cdi-dev] Should javax.enterprise.inject.Produces be
inherited?
Sent by: cdi-dev-bounces at lists.jboss.org
@Matej - Yes, that would be consistent with what I was seeing as well.
@Mark - Are you thinking about decorators and not alternatives? See also
[1]
Really the goal here is to substitute the bean, but not just the provided
bean the producer method that it exposes. It seems to work as I would
expect it in weld (as mentioned), when I add @Produces to the method, it
overrides the base class's producer method. No ambiguous resolutions, it
just works properly.
Realistically, this is all an experiment to see if I can provide spring
boot like default configurations (beans, config values, etc) in a
framework, and override them as an application developer.
[1]: http://docs.jboss.org/cdi/spec/2.0.EDR2/cdi-spec.html#alternatives
From: Matej Novotny <manovotn at redhat.com>
Sent: Monday, September 12, 2016 3:28 AM
To: Mark Struberg
Cc: John Ament; Emily Jiang; cdi-dev
Subject: Re: [cdi-dev] Should javax.enterprise.inject.Produces be
inherited?
Hi all,
I did some testing (with Weld) and it seems the scope IS inherited when
you use @Alternative.
However it IS NOT inherited when you use @Specialized.
Not yet sure if this is intended or anyhow spec-defined, just stating
facts.
Matej
----- Original Message -----
> From: "Mark Struberg" <struberg at yahoo.de>
> To: "John Ament" <john.ament at spartasystems.com>, "Emily Jiang"
<EMIJIANG at uk.ibm.com>
> Cc: "cdi-dev" <cdi-dev at lists.jboss.org>
> Sent: Monday, September 12, 2016 8:00:55 AM
> Subject: Re: [cdi-dev] Should javax.enterprise.inject.Produces be
inherited?
>
>
>
> > Right now inheritance of managed beans is itself problematic, as
>
> > injecting the base class can cause these ambiguous resolutions.
>
> Yes, that's why we originally introduced @Typed.
>
>
>
> Your sample wont work as an Alternative as it extends a concrete class
and
> doesn't implement any interface.
> Did you mean @Specializes?
> Note that with @Alternative you won't make the original producer go
away.You
> would also need to add @Alternative to the producer method imo. The
rules
> for making an alternative producer method are really a bit confusing ;)
I
> think the most portable way is to annotate both the class and the
producer
> method with @Alternative.
>
>
> LieGrue,
> strub
>
>
> On Monday, 12 September 2016, 0:57, John Ament
<john.ament at spartasystems.com>
> wrote:
> >
> >Hi Emily,
> >
> >
> >I disagree, at least it doesn't add any new ambiguous injections. The
> >use-case is specifically to Specialized/Alternative beans. Right now
> >inheritance of managed beans is itself problematic, as injecting the
base
> >class can cause these ambiguous resolutions.
> >
> >
> >The example I sent out actually works correctly (in weld at least),
really
> >my propose is to remove the need to have Produces a second time and
update
> >the spec to clarify what happens here (FWIW, I don't believe the case
is
> >currently described in the spec), hopefully to say that qualifiers and
> >scopes from the base method remain in effect, unless explicitly
overridden.
> >
> >
> >John
> >
> >
> >
> >________________________________
> >
> >From: Emily Jiang <EMIJIANG at uk.ibm.com>
> >Sent: Sunday, September 11, 2016 5:59 PM
> >To: John Ament
> >Cc: cdi-dev
> >Subject: Re: [cdi-dev] Should javax.enterprise.inject.Produces be
inherited?
> >
> >I think this is very problematic as you will get
> >AmbiguousResolutionException all the time once we introduce this
> >inheritance.
> >
> >Many thanks,
> >Emily
> >===========================
> >Emily Jiang
> >WebSphere Application Server, CDI Development Lead
> >
> >MP 211, DE3A20, Winchester, Hampshire, England, SO21 2JN
> >Phone: +44 (0)1962 816278 Internal: 246278
> >
> >Email: emijiang at uk.ibm.com
> >Lotus Notes: Emily Jiang/UK/IBM at IBMGB
> >
> >
> >
> >
> >From: John Ament <john.ament at spartasystems.com>
> >To: cdi-dev <cdi-dev at lists.jboss.org>
> >Date: 11/09/2016 20:04
> >Subject: [cdi-dev] Should javax.enterprise.inject.Produces be
> >inherited?
> >Sent by: cdi-dev-bounces at lists.jboss.org
> >>________________________________
> >
> >
> >
> >All,
> >
> >I was just thinking about alternatives and producer methods. Suppose I
have
> >the following bean:
> >
> >@ApplicationScoped
> >public class Boop {
> >
> > @Produces
> > @ApplicationScoped
> > public Simpler makeSimpler() {
> > return new Simpler("Boop");
> > }
> >}
> >
> >If I want to override the producer method, I need to declare fully:
> >
> >@Alternative
> >@Priority(100)
> >@ApplicationScoped
> >public class BoopAlternative extends Boop{
> > @Override
> > @Produces
> > public Simpler makeSimpler() {
> > return new Simpler("Boop2");
> > }
> >}
> >
> >For some reason, scopes are inherited, but the produces annotation is
not.
> >At least in the case of a producer method, it seems like it would be
> >useful for @Produces to be inherited as well.
> >
> >John
> >
> >________________________________
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