On 1/29/12 12:56, Sven Strohschein wrote:
Hi,
I have built a small plugin system with OSGi. Every plugin-bundle
registers a PluginService. Now I would like to validate the
registered/started plugin bundles/services. For example I would like
to check if an icon is available within the bundle classpath.
I tried to implement a ServiceTracker which validates the bundle on
"ServiceTracker.addingService(...)" and when the validation is failed,
the validated bundle gets stopped via
"Bundle.stop(Bundle.STOP_TRANSIENT)". This does work in some cases,
but sometimes Felix throws a NullPointerException.
It is considered bad practice to change the state of a bundle which is
the subject of the event in a synchronous callback because typically the
framework is in an awkward state at this point (usually holding locks).
Somewhere in the spec, there are some words to this effect.
Besides, you can't pull the rug out from underneath a bundle in the
middle of it trying to do something like register a service.
Maybe it is not the best solution to stop the bundles within a
ServiceTracker. Is there another way to implement a validation mechanizm?
I'm not sure. You might be able to do this in iPOJO by creating a custom
handler that could validate component services and if they were valid
annotate them with some specific "validated" service property. It
wouldn't stop components from registering services, but it would make it
easy for you to only look at valid services.
Perhaps a simpler approach is to simply make all your conditions service
properties if possible, so you can just query for their existence.
-> richard
Thank you in advance.
Here is the NullPointerException which is sometimes thrown by Felix.
ERROR: Bundle org.apache.felix.bundlerepository [26] EventDispatcher:
Error during dispatch. (java.lang.NullPointerException)
java.lang.NullPointerException
at
org.apache.felix.bundlerepository.impl.LocalRepositoryImpl.serviceChanged(LocalRepositoryImpl.java:71)
at
org.apache.felix.framework.util.EventDispatcher.invokeServiceListenerCallback(EventDispatcher.java:932)
at
org.apache.felix.framework.util.EventDispatcher.fireEventImmediately(EventDispatcher.java:793)
at
org.apache.felix.framework.util.EventDispatcher.fireServiceEvent(EventDispatcher.java:543)
at org.apache.felix.framework.Felix.fireServiceEvent(Felix.java:4252)
at org.apache.felix.framework.Felix.registerService(Felix.java:3275)
at
org.apache.felix.framework.BundleContextImpl.registerService(BundleContextImpl.java:346)
at
org.apache.felix.scr.impl.manager.AbstractComponentManager.registerService(AbstractComponentManager.java:449)
at
org.apache.felix.scr.impl.manager.AbstractComponentManager.registerComponentService(AbstractComponentManager.java:460)
at
org.apache.felix.scr.impl.manager.AbstractComponentManager$Unsatisfied.activate(AbstractComponentManager.java:1009)
at
org.apache.felix.scr.impl.manager.AbstractComponentManager.activateInternal(AbstractComponentManager.java:333)
at
org.apache.felix.scr.impl.manager.AbstractComponentManager.enable(AbstractComponentManager.java:157)
at
org.apache.felix.scr.impl.config.ConfiguredComponentHolder.enableComponents(ConfiguredComponentHolder.java:256)
at
org.apache.felix.scr.impl.BundleComponentActivator.loadDescriptor(BundleComponentActivator.java:253)
at
org.apache.felix.scr.impl.BundleComponentActivator.initialize(BundleComponentActivator.java:147)
at
org.apache.felix.scr.impl.BundleComponentActivator.<init>(BundleComponentActivator.java:111)
at
org.apache.felix.scr.impl.Activator.loadComponents(Activator.java:285)
at
org.apache.felix.scr.impl.Activator.bundleChanged(Activator.java:203)
at
org.apache.felix.framework.util.EventDispatcher.invokeBundleListenerCallback(EventDispatcher.java:868)
at
org.apache.felix.framework.util.EventDispatcher.fireEventImmediately(EventDispatcher.java:789)
at
org.apache.felix.framework.util.EventDispatcher.fireBundleEvent(EventDispatcher.java:514)
at org.apache.felix.framework.Felix.fireBundleEvent(Felix.java:4236)
at org.apache.felix.framework.Felix.startBundle(Felix.java:1923)
at
org.apache.felix.framework.Felix.setActiveStartLevel(Felix.java:1191)
at
org.apache.felix.framework.FrameworkStartLevelImpl.run(FrameworkStartLevelImpl.java:295)
at java.lang.Thread.run(Thread.java:662)
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