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https://issues.apache.org/jira/browse/LOG4J2-1971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16085022#comment-16085022
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Ralph Goers commented on LOG4J2-1971:
-------------------------------------
Yes - you can read about OSGi and ServiceLoader at
http://blog.osgi.org/2013/02/javautilserviceloader-in-osgi.html. We switched to
use ServiceLoader because the Java 9 module system requires that to do what we
are doing. Ironically, it seems to make things more difficult with OSGi.
However, when I looked at the way our Activator works it looked to me like it
should work fine out of the box and we wouldn't need the mechanisms discussed
in the blog entry, and it does work in our unit tests.
> ClassCastException: org.eclipse.osgi.internal.loader.SystemBundleLoader$1
> cannot be cast to java.lang.ClassLoader
> -----------------------------------------------------------------------------------------------------------------
>
> Key: LOG4J2-1971
> URL: https://issues.apache.org/jira/browse/LOG4J2-1971
> Project: Log4j 2
> Issue Type: Bug
> Affects Versions: 2.8
> Reporter: liwenxian2017
> Fix For: 2.9
>
>
> When I migrated log4j from log4j 1.2.17 to log4j 2.8, There is an Exception
> like this:
> java.lang.ClassCastException:
> org.eclipse.osgi.internal.loader.SystemBundleLoader$1 cannot be cast to
> java.lang.ClassLoaderat
> org.eclipse.osgi.internal.resolver.BundleDescriptionImpl$DescriptionWiring.getClassLoader(BundleDescriptionImpl.java:1229)
> ~[org.eclipse.osgi.jar:?]at
> org.apache.logging.log4j.core.osgi.Activator.scanBundleForPlugins(Activator.java:70)
> ~[log4j-core.jar:2.8]at
> org.apache.logging.log4j.core.osgi.Activator.bundleChanged(Activator.java:91)
> ~[log4j-core.jar:2.8]at
> org.eclipse.osgi.framework.internal.core.BundleContextImpl.dispatchEvent(BundleContextImpl.java:847)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.internal.core.Framework.publishBundleEventPrivileged(Framework.java:1568)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.internal.core.Framework.publishBundleEvent(Framework.java:1504)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.internal.core.Framework.publishBundleEvent(Framework.java:1499)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.internal.core.StartLevelManager.doSetStartLevel(StartLevelManager.java:247)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:438)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:1)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
> ~[org.eclipse.osgi.jar:?]at
> org.eclipse.osgi.framework.eventmgr.EventManager$EventThread.run(EventManager.java:340)
> ~[org.eclipse.osgi.jar:?]
> I checked Activator.java in log4j-core:
> ...
> 86 @Override
> 87 public void bundleChanged(final BundleEvent event) {
> 88 switch (event.getType()) {
> 89 // FIXME: STARTING instead of STARTED?
> 90 case BundleEvent.STARTED:
> 91 scanBundleForPlugins(event.getBundle());
> 92 break;
> in line 91, it called scanBundleForPlugins for every bundles. But in line
> 60-61, it does not scan system bundle for plugins
> 57 private static void scanInstalledBundlesForPlugins(final BundleContext
> context) {
> 58 final Bundle[] bundles = context.getBundles();
> 59 for (final Bundle bundle : bundles) {
> 60 // LOG4J2-920: don't scan system bundle for plugins
> 61 if (bundle.getState() == Bundle.ACTIVE && bundle.getBundleId() != 0)
> {
> 62 // TODO: bundle state can change during this
> 63 scanBundleForPlugins(bundle);
> And org.eclipse.osgi_3.8.1 's bundle ID is just 0. So it skipped bundle
> org.eclipse.osgi in line 61-63. but it does not in line 91
> If I changed line 91 to:
> if (event.getBundle().getState() == Bundle.ACTIVE &&
> event.getBundle().getBundleId() != 0) {
> scanBundleForPlugins(event.getBundle());
> }
> The exception goes away.
> So is this a bug? Or this is NOT a bug and there is a workaround for this
> Exception? Thanks.
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