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https://issues.apache.org/jira/browse/FELIX-5570?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15906410#comment-15906410
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David Jencks commented on FELIX-5570:
-------------------------------------
Well, I replaced that logic in the proposal. At the moment I think doing
nothing in DS is the best choice. If you want to avoid a log message, make the
WeavingHood delayed and use the DelayedKeepInstances felix extension.
> Immediate service component that provides a WeavingHook results in an NPE
> -------------------------------------------------------------------------
>
> Key: FELIX-5570
> URL: https://issues.apache.org/jira/browse/FELIX-5570
> Project: Felix
> Issue Type: Bug
> Components: Declarative Services (SCR)
> Affects Versions: scr-2.0.8
> Reporter: Thomas Watson
>
> If you have an immediate service component that provides a WeavingHook
> service then an NPE will result. An example service component XML:
> <?xml version="1.0" encoding="UTF-8"?>
> <scr:component xmlns:scr="http://www.osgi.org/xmlns/scr/v1.1.0";
> enabled="true" immediate="true" name="Test Patches Weaver">
> <implementation class="test.patches.Weaver" />
> <service>
> <provide interface="org.osgi.framework.hooks.weaving.WeavingHook"/>
> </service>
> </scr:component>
> If you deploy this bundle along with SCR 2.0.8 on Felix Framework 5.6.2 the
> following NPE happens:
> ERROR: [Test Patches Weaver(0)] Error during instantiation of the
> implementation object
> java.lang.NullPointerException
> at
> org.apache.felix.scr.impl.manager.SingleComponentManager.createImplementationObject(SingleComponentManager.java:237)
> at
> org.apache.felix.scr.impl.manager.SingleComponentManager.createComponent(SingleComponentManager.java:109)
> at
> org.apache.felix.scr.impl.manager.SingleComponentManager.getService(SingleComponentManager.java:906)
> at
> org.apache.felix.scr.impl.manager.SingleComponentManager.getServiceInternal(SingleComponentManager.java:879)
> at
> org.apache.felix.scr.impl.manager.SingleComponentManager.getService(SingleComponentManager.java:823)
> at
> org.apache.felix.framework.ServiceRegistrationImpl.getFactoryUnchecked(ServiceRegistrationImpl.java:347)
> at
> org.apache.felix.framework.ServiceRegistrationImpl.getService(ServiceRegistrationImpl.java:247)
> at
> org.apache.felix.framework.ServiceRegistry.getService(ServiceRegistry.java:350)
> at org.apache.felix.framework.Felix.getService(Felix.java:3720)
> at
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.transformClass(BundleWiringImpl.java:2359)
> at
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.findClass(BundleWiringImpl.java:2052)
> at
> org.apache.felix.framework.BundleWiringImpl.findClassOrResourceByDelegation(BundleWiringImpl.java:1518)
> at
> org.apache.felix.framework.BundleWiringImpl.access$200(BundleWiringImpl.java:79)
> at
> org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.loadClass(BundleWiringImpl.java:1958)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
> at org.apache.felix.framework.Felix.loadBundleClass(Felix.java:1925)
> at org.apache.felix.framework.BundleImpl.loadClass(BundleImpl.java:978)
> at
> org.apache.felix.scr.impl.manager.AbstractComponentManager.initDependencyManagers(AbstractComponentManager.java:976)
> at
> org.apache.felix.scr.impl.manager.AbstractComponentManager.collectDependencies(AbstractComponentManager.java:1003)
> at
> org.apache.felix.scr.impl.manager.SingleComponentManager.getServiceInternal(SingleComponentManager.java:859)
> at
> org.apache.felix.scr.impl.manager.AbstractComponentManager.activateInternal(AbstractComponentManager.java:749)
> at
> org.apache.felix.scr.impl.manager.AbstractComponentManager.enableInternal(AbstractComponentManager.java:675)
> at
> org.apache.felix.scr.impl.manager.AbstractComponentManager.enable(AbstractComponentManager.java:430)
> at
> org.apache.felix.scr.impl.manager.ConfigurableComponentHolder.enableComponents(ConfigurableComponentHolder.java:657)
> at
> org.apache.felix.scr.impl.BundleComponentActivator.initialEnable(BundleComponentActivator.java:341)
> at
> org.apache.felix.scr.impl.Activator.loadComponents(Activator.java:390)
> at org.apache.felix.scr.impl.Activator.access$200(Activator.java:54)
> at
> org.apache.felix.scr.impl.Activator$ScrExtension.start(Activator.java:265)
> at
> org.apache.felix.utils.extender.AbstractExtender.createExtension(AbstractExtender.java:254)
> at
> org.apache.felix.utils.extender.AbstractExtender.modifiedBundle(AbstractExtender.java:227)
> at
> org.apache.felix.utils.extender.AbstractExtender.addingBundle(AbstractExtender.java:187)
> at
> org.osgi.util.tracker.BundleTracker$Tracked.customizerAdding(BundleTracker.java:469)
> at
> org.osgi.util.tracker.BundleTracker$Tracked.customizerAdding(BundleTracker.java:415)
> at
> org.osgi.util.tracker.AbstractTracked.trackAdding(AbstractTracked.java:256)
> at org.osgi.util.tracker.AbstractTracked.track(AbstractTracked.java:229)
> at
> org.osgi.util.tracker.BundleTracker$Tracked.bundleChanged(BundleTracker.java:444)
> at
> org.apache.felix.framework.EventDispatcher.invokeBundleListenerCallback(EventDispatcher.java:915)
> at
> org.apache.felix.framework.EventDispatcher.fireEventImmediately(EventDispatcher.java:834)
> at
> org.apache.felix.framework.EventDispatcher.fireBundleEvent(EventDispatcher.java:516)
> at org.apache.felix.framework.Felix.fireBundleEvent(Felix.java:4562)
> at org.apache.felix.framework.Felix.activateBundle(Felix.java:2229)
> at org.apache.felix.framework.Felix.startBundle(Felix.java:2144)
> at org.apache.felix.framework.Felix.setActiveStartLevel(Felix.java:1371)
> at
> org.apache.felix.framework.FrameworkStartLevelImpl.run(FrameworkStartLevelImpl.java:308)
> at java.lang.Thread.run(Thread.java:745)
> This is because SCR is invoking SingleComponentManager.getServiceInternal
> after registering the WeavingHook service in order to get the service object
> for immediate activation. This ends up trying to load the
> test.patches.Weaver implementation class which then causes the framework to
> look for WeavingHooks to call. Which causes a recursive call back into
> SingleComponentManager.getServiceInternal for the same service component
> which triggers another load of the implementation class. Here Felix
> framework detects a recursive class load for the same class name and returns
> null from Bundle.loadClass() (Something I think is not correct, I think
> instead a CNFE must be thrown or some other class loader LinkageError).
> This null class results in the above NPE. I found this bug while running SCR
> on the Equinox framework. On Equinox a CNFE is thrown and logged by SCR and
> things seem to recover from that but we are left with an error message in the
> log making it look like things are not working.
> Both Equinox and Felix seem to detect the recursive class load that SCR is
> causing but handle the situation slightly different. In both cases I argue
> that SCR should avoid recursive calls into
> SingleComponentManager.getServiceInternal for the same service component.
> The difficulty here is that SCR can depend on the framework to avoid
> recursive calls into its ServiceFactory because the specification mandates
> that (see org.osgi.framework.ServiceException.FACTORY_RECURSION). But here
> SCR is invoking SingleComponentManager.getServiceInternal itself and an
> internal implementation detail of an immediate service component. It seems
> that for this internal call to SingleComponentManager.getServiceInternal
> something should be done to prevent recurse calls so that this is consistent
> with how non-immediate components work.
> Also see https://bugs.eclipse.org/bugs/show_bug.cgi?id=512707
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