Strange null exception on Tomcat 6.0.18

[Slawek Ch]

I have a big problem with removing attributes by Tomcat 6.0.18. This happens after migrating from Tomcat 5.5.23 (on this version there wasn't such error). Exception occur occasionally and for now I don't know how to resolve it. Below there is a stack trace from error:

2008-10-16 07:53:52 org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet Faces Servlet threw exception
java.lang.NullPointerException
at org.apache.catalina.connector.Request.removeAttribute(Request.java:1354)
at org.apache.catalina.connector.RequestFacade.removeAttribute(RequestFacade.java:514)
at org.apache.myfaces.context.servlet.RequestMap.removeAttribute(RequestMap.java:59)
at org.apache.myfaces.util.AbstractAttributeMap.remove(AbstractAttributeMap.java:124)
at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.unsetScope(FacesCompositeELResolver.java:163)
at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.invoke(FacesCompositeELResolver.java:152)
at org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:104)
at org.apache.myfaces.el.VariableResolverToApplicationELResolverAdapter.resolveVariable(VariableResolverToApplicationELResolverAdapter.java:45)
at org.quamasoft.common.servlets.jsf.JsfServletUtils.getManagedBean(JsfServletUtils.java:52)
at org.quamasoft.common.servlets.jsf.JsfServletUtils.getManagedBean(JsfServletUtils.java:57)
at org.quamasoft.server.filters.LicensedActionServletFilter.doFilter(LicensedActionServletFilter.java:49)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.uhc.filters.JsfAuthenticationFilter.doFilter(JsfAuthenticationFilter.java:67)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.uhc.filters.SessionFilter.doFilter(SessionFilter.java:115)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.quamasoft.server.filters.ServletContextFilter.doFilter(ServletContextFilter.java:69)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)

Anyone know how to resolve it, please?

[William Brogden]

Looking at the source code around line 1354 for Tomcat 6.0.18 we find:

         // Notify interested application event listeners
        Object listeners[] = context.getApplicationEventListeners();
        if ((listeners == null) || (listeners.length == 0))
   

Looks like if context is null you get an NPE

Around line 500 there are setContext and getContext methods - this is the normal javax.servlet.ServletContext we are talking about.

To further track this down, you might try calling the request getContext method to see if it is null before calling the removeAtribute method.

Bill

[Slawek Ch]

Now I'm using Tomcat 6.0.9 problem doesn't occur. It happens only from version 6.0.10 or higher. Maybe it is Tomcat new bug.

Anyway thanks for suggestion.