[LOG4J2-373] Classloader issue in OSGi-environment

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.0-beta9
• Fix Version/s: 2.0.1
• Component/s: API, Core
• Labels: ClassLoader OSGI

Environment

OSGi R5 / R4 (Apache Felix 4.x)

• Epic Link: OSGi Support
• Assignee: Matt Sicker
• Reporter: Roland Weiglhofer
• Created: 27/Aug/13 07:19
• Updated: 03/Dec/15 17:11
• Resolved: 20/Jul/14 02:16

Description

Using Log4j2 in a bundle causes following error:
ERROR StatusLogger org.apache.logging.log4j.core.impl.Log4jContextFactory does not implement org.apache.logging.log4j.spi.LoggerContextFactory
ERROR StatusLogger Unable to locate a logging implementation, using SimpleLogger

printing the ClassLoaders in LogManager gives me following output:

org.apache.logging.log4j.spi.LoggerContextFactory loaded by org.apache.logging.log4j-api [13]
org.apache.logging.log4j.core.impl.Log4jContextFactory loaded by sun.misc.Launcher$AppClassLoader@35a16869

We have two different ClassLoaders. That's why the implementation is not assignable. The core uses the bootstrap-classloader and the api uses the bundle-classloader.

Workaround needed. Thx

addendum:
ProviderUtil.findClassLoader() returns the bootstrap-classloader but not the bundle-classloader of the log4j2-core. The log4j2-core is a fragment of the log4j2-api bundle. Thus, ProviderUtil.findClassLoader() must return the bundle-classloader of log4j2-api. This a bug for the case that log4j2-core is used as the implementation. There are other cases that will also cause problems. Further investigations are necessary.

Workaround:
1. check if log4j2 runs in an OSGI container.
Bundle mybundle = org.osgi.framework.FrameworkUtil.getBundle(MyClass.this);
2. if(mybundle != null), than get bundle-classloader of log4j2-impl.
mybundle.adapt(BundleWiring.class).getClassLoader();

Issue Links

• is related to: LOG4J2-513 Use more OSGi-friendly class loading mechanisms.