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From "Felix Meschberger (JIRA)" <j...@apache.org>
Subject [jira] Commented: (FELIX-1754) Usage of BundleContext.getServiceReferences results in failure to activate components
Date Wed, 14 Oct 2009 05:26:31 GMT

    [ https://issues.apache.org/jira/browse/FELIX-1754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12765400#action_12765400
] 

Felix Meschberger commented on FELIX-1754:
------------------------------------------

Well, actually, the resolution is -- unfortunately for you -- quite easy and clearly described
in the spec (Section 112.3 References to Services in the R4.2 Compendium Manual, DS 1.1):


          The services that are selected by a reference are called the target services.
          These are the services selected by the BundleContext.getServiceReferences
          method where the first argument is the reference's interface and the second
          argument is the reference's target property, which must be a valid filter.

So, the spec refers to the getServiceReferences method and using the getAllServiceReferences
method is therefore in my understanding violating the spec.

>From the POV of the Felix DS implementation, I fear there is nothing to be done.


But... what worries me is your output:

   > isClassAccessible: m_factory = Component: foo.bar.event.internal.EventEngineImpl (11)
   > isClassAccessible: m_svcObj = Component: foo.bar.event.internal.EventEngineImpl (11)
   > isClassAccessible: sourceClass= class org.apache.felix.scr.impl.manager.DelayedComponentManager


If you are using SCR to register the service, then m_factory is probably the DelayedComponentManager
instance and not the EventEngineImpl instance ! I think your log output is incorrect.

Anyway, the problem is that an SCR class -- the DelayedComponentManager acting as the ServiceFactory
-- is used to load the interface class, a situation which is definitely wrong. And a situation,
which I assumed Karl has fixed for 2.0.1....

The problem here is, that the m_factory may not be used to verify accessibility since the
service may be registered as a ServiceFactory on behalf of the real bundle. So the actual
provider bundle must probably be used to verify accessibility and not the ServiceFactory object's
class loader.

> Usage of BundleContext.getServiceReferences results in failure to activate components
> -------------------------------------------------------------------------------------
>
>                 Key: FELIX-1754
>                 URL: https://issues.apache.org/jira/browse/FELIX-1754
>             Project: Felix
>          Issue Type: Bug
>          Components: Declarative Services (SCR)
>    Affects Versions: scr-1.2.0
>            Reporter: Matthew Sykes
>         Attachments: felix-1754.diff
>
>
> I'm attempting to move some code from Equinox to Felix that makes use of the declarative
services 1.1 runtime.  Many of the components in our bundles declare multiple 'provide' elements
in the service declaration .  In general these services consist of a standardized interface
in one package and extensions to that interface in another.  Depending on the requirements
of the code using the component, other bundles will declare their components with references
to either the standardized interface or the extended interface.
> The issue I'm seeing is that the Felix SCR fails to activate some components because
it's failing to resolve references to the service provided by another component.  It turns
out that the SCR is using BundleContext.getServiceReferences instead of BundleContext.getAllServiceReferences
to locate candidate services when resolving references.  Unfortunately, the getServiceReference
flavor requires that the using bundle have access to all class names under which the target
service was registered - not just the interface associated with the reference.
> Given the use-case I've described and the behavior of Equinox, I believe the Felix SCR
should be using BundleContext.getAllServiceReferences(..) to resolve references and rely on
the bundle creator to define the correct imports.

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