急！！！在线等！webwork + tomcat (安装版的) 正常用的时候都没有问题，可是这次培训，并发的用户数在40个左右，出问题了

过几分钟就出现下面的问题了，tomcat重新启动后，又可以以了，但是过几分钟又不能用，只能一直重新启动，各位大虾帮忙看看什么问题，不胜感激！！[ERROR] [default].invoke(253) | Servlet.service() for servlet default threw exception
java.lang.NoClassDefFoundError: javax/portlet/PortletRequest
at com.opensymphony.webwork.portlet.context.PortletActionContext.getRequest(PortletActionContext.java:70)
at com.opensymphony.webwork.portlet.context.PortletActionContext.isPortletRequest(PortletActionContext.java:94)
at com.opensymphony.webwork.components.URL.end(URL.java:187)
at com.opensymphony.webwork.views.freeer.tags.CallbackWriter.afterBody(CallbackWriter.java:65)
at freeer.core.Environment.visit(Environment.java:235)
at freeer.core.UnifiedCall.accept(UnifiedCall.java:116)
at freeer.core.Environment.visit(Environment.java:196)
at freeer.core.MixedContent.accept(MixedContent.java:92)
at freeer.core.Environment.visit(Environment.java:196)
at freeer.core.ConditionalBlock.accept(ConditionalBlock.java:79)
at freeer.core.Environment.visit(Environment.java:196)
at freeer.core.Environment.process(Environment.java:176)
at freeer.template.Template.process(Template.java:231)
at com.opensymphony.webwork.components.template.FreeerTemplateEngine.renderTemplate(FreeerTemplateEngine.java:122)
at com.opensymphony.webwork.components.UIBean.mergeTemplate(UIBean.java:334)
at com.opensymphony.webwork.components.UIBean.end(UIBean.java:291)
at com.opensymphony.webwork.views.jsp.ComponentTagSupport.doEndTag(ComponentTagSupport.java:21)
at org.apache.jsp.WEB_002dINF.pages.ComMgt.switchProject_jsp._jspx_meth_ww_head_0(switchProject_jsp.java:308)
at org.apache.jsp.WEB_002dINF.pages.ComMgt.switchProject_jsp._jspService(switchProject_jsp.java:90)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:672)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:463)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:398)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
at com.opensymphony.webwork.dispatcher.ServletDispatcherResult.doExecute(ServletDispatcherResult.java:114)
at com.opensymphony.webwork.dispatcher.WebWorkResultSupport.execute(WebWorkResultSupport.java:101)
at com.opensymphony.xwork.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:300)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:198)
at com.opensymphony.xwork.interceptor.DefaultWorkflowInterceptor.intercept(DefaultWorkflowInterceptor.java:125)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.webwork.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:136)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:146)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:32)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:94)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:180)
at com.opensymphony.xwork.DefaultActionProxy.execute(DefaultActionProxy.java:113)
at com.opensymphony.webwork.dispatcher.DispatcherUtils.serviceAction(DispatcherUtils.java:202)
at com.opensymphony.webwork.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:184)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Unknown Source)