is below caused by user session expired? if yes, how to exend session on tapestry 4 ? or any other way to solve this problem?

Unable to process client request: Unable to forward to local resource '/app?service=page&page=Home&id=692': java.lang.NullPointerException: Property 'webRequest' of <OuterProxy for tapestry.globals.RequestGlobals(org.apache.tapestry.services.RequestGlobals)> is null.


Apr 22, 2010 5:14:43 PM org.apache.catalina.core.ApplicationContext log
SEVERE: app: ServletException
javax.servlet.ServletException: java.lang.NullPointerException: Property 'webRequest' of <OuterProxy for tapestry.globals.RequestGlobals(org.apache.tapestry.services.RequestGlobals)> is null.
 at org.apache.tapestry.services.impl.WebRequestServicerPipelineBridge.service(WebRequestServicerPipelineBridge.java:65)
 at $ServletRequestServicer_128043b52ea.service($ServletRequestServicer_128043b52ea.java)
 at org.apache.tapestry.request.DecodedRequestInjector.service(DecodedRequestInjector.java:55)
 at $ServletRequestServicerFilter_128043b52e6.service($ServletRequestServicerFilter_128043b52e6.java)
 at $ServletRequestServicer_128043b52ec.service($ServletRequestServicer_128043b52ec.java)
 at org.apache.tapestry.multipart.MultipartDecoderFilter.service(MultipartDecoderFilter.java:52)
 at $ServletRequestServicerFilter_128043b52e4.service($ServletRequestServicerFilter_128043b52e4.java)
 at $ServletRequestServicer_128043b52ec.service($ServletRequestServicer_128043b52ec.java)
 at org.apache.tapestry.services.impl.SetupRequestEncoding.service(SetupRequestEncoding.java:53)
 at $ServletRequestServicerFilter_128043b52e8.service($ServletRequestServicerFilter_128043b52e8.java)
 at $ServletRequestServicer_128043b52ec.service($ServletRequestServicer_128043b52ec.java)
 at $ServletRequestServicer_128043b52de.service($ServletRequestServicer_128043b52de.java)
 at org.apache.tapestry.ApplicationServlet.doService(ApplicationServlet.java:126)
 at org.apache.tapestry.ApplicationServlet.doPost(ApplicationServlet.java:171)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:378)
 at org.springframework.security.intercept.web.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109)
 at org.springframework.security.intercept.web.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
 at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390)
 at org.springframework.security.ui.SessionFixationProtectionFilter.doFilterHttp(SessionFixationProtectionFilter.java:67)
 at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53)
 at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390)
 at org.springframework.security.ui.ntlm.NtlmProcessingFilter.doFilterHttp(NtlmProcessingFilter.java:358)
 at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53)
 at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390)
 at org.springframework.security.ui.ExceptionTranslationFilter.doFilterHttp(ExceptionTranslationFilter.java:101)
 at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53)
 at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390)
 at org.springframework.security.context.HttpSessionContextIntegrationFilter.doFilterHttp(HttpSessionContextIntegrationFilter.java:235)
 at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53)
 at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390)
 at org.springframework.security.concurrent.ConcurrentSessionFilter.doFilterHttp(ConcurrentSessionFilter.java:99)
 at org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53)
 at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390)
 at org.springframework.security.util.FilterChainProxy.doFilter(FilterChainProxy.java:175)
 at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:236)
 at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
 at org.apache.coyote.http11.Http11Protocol$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)