I’ve been bugged by this problem for some time now, so I decided to investigate a bit. The error shows up when tomcat is trying to reload the web application.

SEVERE: Error reading tld listeners java.lang.NullPointerException
java.lang.NullPointerException
at org.apache.log4j.Category.isEnabledFor(Category.java:746)
at org.apache.commons.logging.impl.Log4JLogger.isTraceEnabled(Log4JLogger.java:327)
at org.apache.catalina.startup.TldConfig.tldScanResourcePaths(TldConfig.java:582)
at org.apache.catalina.startup.TldConfig.execute(TldConfig.java:283)
at org.apache.catalina.core.StandardContext.processTlds(StandardContext.java:4307)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4144)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3025)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:432)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1278)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1570)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1579)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1579)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1559)
at java.lang.Thread.run(Thread.java:595)

The solution is quite simple: replace commons-logging.jar from your 1.1 version with a previous version (1.0.4). That’s it. The problem has been discussed here.

technorati tags: java, tomcat, reload, application, commons-login