Class Loading Problem with log4j and Eclipse

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Problem: Eclipse has problems with the class loading of log4j (also applicable for the log4j available from Eclipse Orbit). log4j uses classForName which conflicts with the class loader of Eclipse.

Caused by: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@1692b33 for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category) (Caused by org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@1692b33 for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category))
    at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543)
    at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235)
    at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209)
    at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351)
    at org.eclipse.xtend.expression.ExecutionContextImpl.<clinit>(ExecutionContextImpl.java:51)
    ... 15 more
Caused by: org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@1692b33 for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category)
    at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:413)
    at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529)
    ... 19 more
Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/Category
    at java.lang.Class.getDeclaredConstructors0(Native Method)
    at java.lang.Class.privateGetDeclaredConstructors(Unknown Source)
    at java.lang.Class.getConstructor0(Unknown Source)
    at java.lang.Class.getConstructor(Unknown Source)
    at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:410)
    ... 20 more
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Category
    at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:489)
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:405)
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:393)
    at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:105)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    ... 25 more

Solution: use the PCM logging bridge: SVN (User: anonymous; Password: anonymous). Checkout the plugin org.apache.commons.logging.fragment from Palladio.Wrapper into the workspace.

The above fragment extends apache.commons.logging in such a way that it can access classes from the log4j plugin.

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Keywords: log4j, Apache, Eclipse, Class Loader, ClassNotFoundException, NoClassDefFoundError, logging, Plugin, classForName