Hi Dan,
yes you can use the OSGi annotations with the scr plugin, you need to add
this dependency to your project:
<groupId>org.apache.felix</groupId>
<artifactId>org.apache.felix.scr.ds-annotations</artifactId>
<version>1.2.4</version>
Carsten
2013/11/2 Daniel McGreal <[email protected]>
> Hi Carsten,
> Thanks a lot for your reply.
>
> Are you saying that one can use the OSGi annotations with the
> Maven-SCR-Plugin? I thought I tried this initially, without success - but
> thinking about it, I may have been misled because maven complained I didn’t
> have the “AnnotationProcessor” (or similar) when I didn’t have the
> scr.annotations bundle as a dependency - maybe I just assumed that having
> included the annotations bundle, those were the annotations I should be
> using.
>
> If this is the case, no need for an feature request I think.
>
> Best, Dan.
>
> On 2 Nov 2013, at 15:12, Carsten Ziegeler <[email protected]> wrote:
>
> > Hi,
> >
> > as Robert wrote, the scr annotations from the Apache Felix project
> predate
> > the annotations from the spec. Regardless of which annotations you use,
> the
> > result is compliant to the DS specification: a descriptor XML is
> generated
> > containing the references and for each reference the methods for bind and
> > unbind are listed and these methods must exist in the contained class.
> > While the Reference annotations from the OSGi spec is more pure in the
> > sense that you annotate the bind method, the one from Apache Felix is
> more
> > convenient at least for unnary references as you just annotate the field
> > and the methods are generated for you.
> > If you want to mimic the same behaviour, you have to use a Reference
> > annotation on the class as explained by Robert as well.
> > We could add support for annotation a method like the OSGi annotations
> do,
> > you might want to create a feature request issue for this
> >
> > Regards
> > Carsten
> >
> >
> > 2013/11/2 Robert Munteanu <[email protected]>
> >
> >> On Sat, Nov 2, 2013 at 4:04 PM, Daniel McGreal <[email protected]>
> wrote:
> >>> Thanks again Robert,
> >>>
> >>>> I'm not sure about the reason behind it, but I think that the
> >>>> Felix-specific SCR annotations predate the OSGi spec for annotations.
> >>>
> >>>
> >>> That occurred to me, but the naming was so similar that I ignored it.
> >> SCR has been very inspirational then!
> >>> In that case, would it be an idea to extend the annotation’s target to
> >> methods as well as fields?
> >>
> >> Maybe. Hopefully SCR devs can chime in regarding this design decision.
> >>
> >>>
> >>>> Hm, have you tried setting the property annotation on the class,
> >>>> rather than a field?
> >>>
> >>>
> >>> In my case, the value must be computed and retrieved from an external
> >> source (the first time) but can then be cached and expected not to
> change,
> >> which is why I have a service to provide it. I wonder how I could
> achieve
> >> that with configuration?
> >>
> >>
> >> What I mean was writing something like ( not tested )
> >>
> >> @Reference(name="myValue", interfaceReference = MyValue.class)
> >> @Component
> >> public class MyComp {
> >>
> >> protected void bindMyValue(MyValue val) { /* whatever */ }
> >> }
> >>
> >> The only advantage of declaring a Reference on a field is that you
> >> don't have to declare the name and interfaceReference properties,
> >> which are inferred from the field. For more details, see [1].
> >>
> >> Robert
> >>
> >> [1]:
> >>
> http://felix.apache.org/documentation/subprojects/apache-felix-maven-scr-plugin/scr-annotations.html#reference
> >>
> >>>
> >>> Many thanks,
> >>> Dan.
> >>>
> >>> On 2 Nov 2013, at 13:57, Robert Munteanu <[email protected]> wrote:
> >>>
> >>>> On Sat, Nov 2, 2013 at 3:50 PM, Daniel McGreal <[email protected]>
> >> wrote:
> >>>>> Hi Robert,
> >>>>>
> >>>>> Thanks for your reply. I was not actually aware the plugin generated
> >> the methods, that’s very helpful!
> >>>>>
> >>>>> I have implemented the bind method in such a manner, but am forced to
> >> have a pointless (and potentially destructively misleading) field that I
> >> can’t prevent other people from using and therefore have to document
> that
> >> it’s not to be used or put effort into writing the class to ensure it’s
> >> null and thread safe on the reference - a task that would be implicit if
> >> the field never existed. To illustrate, when all is well in my class I
> have
> >> to have a warning that the field is unused, whereas what I need is a
> >> warning if it is!
> >>>>
> >>>> Hm, have you tried setting the property annotation on the class,
> >>>> rather than a field? You might need to use a holder @Properties
> >>>> annotation if you have more than one annotation.
> >>>>
> >>>>>
> >>>>> I am curious as to the rationale of it being a field annotation
> rather
> >> than a method (or method + field), as it must have been a conscious
> choice
> >> to deviate from the way the OSGi spec does it.
> >>>>
> >>>> I'm not sure about the reason behind it, but I think that the
> >>>> Felix-specific SCR annotations predate the OSGi spec for annotations.
> >>>>
> >>>> Robert
> >>>>
> >>>>>
> >>>>> Best, Dan.
> >>>>>
> >>>>>
> >>>>> On 2 Nov 2013, at 13:43, Robert Munteanu <[email protected]> wrote:
> >>>>>
> >>>>>> Hi Dan,
> >>>>>>
> >>>>>> On Sat, Nov 2, 2013 at 3:12 PM, Daniel McGreal <[email protected]>
> >> wrote:
> >>>>>>> Hi Felix users,
> >>>>>>> I wonder if anyone knows why the Felix @Reference annotations are
> >> valid on fields, but not methods, whereas the opposite is true for the
> OSGi
> >> standard @Reference annotation.
> >>>>>>> I would very much like to have a service bound, which I don’t keep
> a
> >> reference to in the rest of my class (so that I can guarantee that code
> in
> >> the rest of the class doesn’t depend directly on the reference). For
> >> example:
> >>>>>>>
> >>>>>>> int value;
> >>>>>>> private void bindValueGetter(ValueGetter s){
> >>>>>>> value = s.getValue();
> >>>>>>> }
> >>>>>>>
> >>>>>>> With the annotation on the field, I am forced to have a reference
> to
> >> the ValueGetter, which might mislead programmers into using it - without
> >> the reference there I can just keep the cached values when the service
> >> arrives the first time and not have to document, etc that it might be
> null.
> >>>>>>
> >>>>>> The maven-scr-plugin ( and I think the ant task as well ) generates
> a
> >>>>>> 'bindValueGetter' method automatically if you don't have it in your
> >>>>>> class. If you implement it yourself, you can control its behaviour,
> >>>>>> just like in your snippet above.
> >>>>>>
> >>>>>> Robert
> >>>>>>
> >>>>>>>
> >>>>>>> Thanks, Dan.
> >>>>>>>
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> >>>>>>>
> >>>>>>
> >>>>>>
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> >>>>>>
> >>>>>
> >>>>>
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> >>>>>
> >>>>
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> >>>
> >>
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> >>
> >>
> >
> >
> > --
> > Carsten Ziegeler
> > [email protected]
>
>
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>
--
Carsten Ziegeler
[email protected]
