Bruce Jackson wrote
> Thank you, Thomas & Neil.
>
> As Neil suggested, the problem is that MyServiceProcessor does rely on the
> BundleContext which obviously I don’t have at that point, otherwise I could
> have used the pattern you both suggested.
> It’s not a big deal to use a ServiceTracker, it just feels a bit ‘old school’
> when using DS for everything else. Perhaps this is something that might be
> considered for future enhancements of the OSGi spec. It feels like it would
> be useful in many circumstances to have reference binding methods that are
> only operational once the component in question is activated?
>
This will actually be addressed with the upcoming update of Declarative
Services in R7 this year. You'll get constructor injection and other
features that help solving exactly such use cases.
Regards
Carsten
> Best regards
>
> Bruce
>
> On 12/05/2017, 10:23, "Thomas Driessen" <thomas.dries...@ds-lab.org> wrote:
>
> Hi Bruce,
>
> why aren't you using the constructor of MyComponent for this?
> Your MyServiceProceessor is neither an OSGi service nor does it need
> something from the @Activate method (e.g. the ComponentContext).
>
> So I would do something like this:
>
> @Component(name="Bar")
> public class MyComponent {
>
> private MyServiceProcessor processor;
>
> public MyComponent(){
> processor = new MyServiceProcessor();
> }
>
> ...
>
> }
>
> This way it is guaranteed that your reference is set before any of the
> bind methods are called.
> You can have a look at
>
> http://enroute.osgi.org/appnotes/concurrency.html Subsection
> "Guarantees from DS"
>
> for a little more information on this.
>
> Kind regards,
> Thomas
>
> ------ Originalnachricht ------
> Von: "Bruce Jackson" <bruce.jack...@myriadgroup.com>
> An: "users@felix.apache.org" <users@felix.apache.org>
> Gesendet: 12.05.2017 09:05:34
> Betreff: Lifecycle and Reference
>
> >Hi Everyone
> >
> >I was wondering if anyone could provide some advice:
> >
> >I have a component of the form:
> >
> >@Component(name="Bar")
> >public class MyComponent {
> >
> >private MyServiceProcessor processor;
> >
> >@Activate
> >public void activate(ComponentContext cc) {
> >
> >processor = new MyServiceProcessor();
> >
> >}
> >
> >@Deactivate
> >public void deactivate(ComponentContext cc) {
> >
> >}
> >
> >@Reference(cardinality = ReferenceCardinality.MULTIPLE)
> >public void bindFoo(ServiceReference<Foo> ref) {
> >
> >/* some code here */
> >processor.process(ref.getService());
> >/* some more code here */
> >
> >}
> >
> >public void unbindFoo(ServiceReference<Foo> ref) {
> >
> >}
> >
> >}
> >
> >The problem here is that the bindFoo() method is called by the SCR
> >before the activate and thus a null pointer exception is thrown in the
> >processor.process() call.
> >This is perhaps not surprising, but it is not ideal for a component
> >that is ‘lazy’ about the other services that it wants to discover. I
> >could clearly move this functionality into a ServiceTracker which I
> >create in the activate() but was wondering if there was another
> >approach that allowed me to do this via DS and annotations?
> >
> >Best regards
> >
> >Bruce
> >
> >
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Adobe Research Switzerland
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