Symptoms

Login fails after an upgrade. The following message appears in the logs:

java.lang.NoClassDefFoundError: org/apache/log4j/PatternLayout 

Cause

Confluence is missing the class "org/apache/log4j/PatternLayout.class," which is a part of log4j library jar file.

Resolution

Move the log4j.jar file from the WEB-INF/lib directory to the /common/lib (Tomcat 5.5) or /lib (Tomcat 6) directory.