dwr reverse 做聊天室遇到的问题.

 今天在用dwr reverse做聊天室．几乎每次都会报这个错误．但是页面显示是正常的。我怀疑是线程的安全设置问题．但是检查了一下午，没什么发现．一直是报的如下的错误．希望高手或者专家指导一下。应该不是包的问题．是配置的地方出的差错？错误如下: WARN [org.directwebremoting.dwrp.JettyContinuationSleeper] - <Exception>java.lang.NullPointerException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at org.directwebremoting.util.Continuation.suspend(Continuation.java:57) at org.directwebremoting.dwrp.JettyContinuationSleeper.goToSleep(JettyContinuationSleeper.java:78) at org.directwebremoting.dwrp.PollHandler.handle(PollHandler.java:207) at org.directwebremoting.servlet.UrlProcessor.handle(UrlProcessor.java:101) at org.directwebremoting.servlet.DwrServlet.doPost(DwrServlet.java:146) at javax.servlet.http.HttpServlet.service(HttpServlet.java:710) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:173) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:77) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685) at java.lang.Thread.run(Thread.java:595)  

谢谢大家！如果有对此熟悉的朋友．请麻烦回答一下．谢谢指教！