Servlet.service() for servlet default threw exception java.lang.NullPointerException

Our system using Struts 2. Sometimes it throws PWC1406: Servlet.service() for servlet default threw exception, but without any stacktrace message. Do anyone can tell me how to get the full stacktrace?

The following are the error message in glassfish 3.1 server.log:

[#|2011-10-04T12:32:18.082+0800|WARNING|glassfish3.1|javax.enterprise.system.container.web.com.sun.enterprise.web|_ThreadID=216;_ThreadName=Thread-2;|StandardWrapperValve[default]: PWC1406: Servlet.service() for servlet default threw exception
    java.lang.NullPointerException
    |#]

[#|2011-10-04T12:32:18.082+0800|SEVERE|glassfish3.1|org.apache.catalina.connector.CoyoteAdapter|_ThreadID=18;_ThreadName=Thread-2;|PWC3989: An exception or error occurred in the container during the request processing
java.lang.NullPointerException
|#]

[#|2011-10-04T12:32:18.082+0800|WARNING|glassfish3.1|javax.enterprise.system.container.web.com.sun.ente开发者_JAVA百科rprise.web|_ThreadID=216;_ThreadName=Thread-2;|Response Error during finishResponse
java.lang.NullPointerException
|#]

[#|2011-10-04T12:32:18.082+0800|SEVERE|glassfish3.1|com.sun.grizzly.config.GrizzlyServiceListener|_ThreadID=18;_ThreadName=Thread-2;|GRIZZLY0037: Error finishing response.
java.lang.NullPointerException
|#]

[#|2011-10-04T12:32:18.082+0800|SEVERE|glassfish3.1|com.sun.grizzly.config.GrizzlyServiceListener|_ThreadID=18;_ThreadName=Thread-2;|GRIZZLY0051: ProcessorTask exception.
java.lang.NullPointerException
|#]

Many thanks.

We won't be able to diagnose this without any stacktraces.

My guess is that the reason you are not seeing stack traces is that your logger has been configured to not output any stacktrace information. So your first step should be to look into that issue.