tomcat - 在 Tomcat 的请求中的 parseParameters 期间间歇性 NPE

Question

我们在 org.apache.catalina.connector.Request 的 parseParemeters 期间有间歇性 NPE。在线的用户越多，这种 NPE 发生的次数就越多。 JBoss 重启后，NPE 会消失一段时间。在 24 小时内，我们收到了 1 到 400 多个 NPE。调用哪个服务并不重要。任何服务请求都可以在此 NPE 中结束。

java.lang.NullPointerException        at org.apache.catalina.connector.Request.parseParameters(Request.java:2517)        at org.apache.catalina.connector.Request.getParameterNames(Request.java:1102)        at org.apache.catalina.connector.Request.getParameterMap(Request.java:1082)        at org.apache.catalina.connector.RequestFacade.getParameterMap(RequestFacade.java:414)        at javax.servlet.ServletRequestWrapper.getParameterMap(ServletRequestWrapper.java:166)        at org.jboss.seam.mock.MockExternalContext.getRequestParameterValuesMap(MockExternalContext.java:307)        at org.jboss.seam.faces.Parameters.getRequestParameters(Parameters.java:61)        at org.jboss.seam.Component.injectParameters(Component.java:1586)        at org.jboss.seam.Component.inject(Component.java:1556)        at org.jboss.seam.core.BijectionInterceptor.aroundInvoke(BijectionInterceptor.java:61)        at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)        at org.jboss.seam.transaction.TransactionInterceptor$1.work(TransactionInterceptor.java:97)        at org.jboss.seam.util.Work.workInTransaction(Work.java:61)        at org.jboss.seam.transaction.TransactionInterceptor.aroundInvoke(TransactionInterceptor.java:91)        at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)        at org.jboss.seam.core.MethodContextInterceptor.aroundInvoke(MethodContextInterceptor.java:44)        at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)        at org.jboss.seam.security.SecurityInterceptor.aroundInvoke(SecurityInterceptor.java:163)        at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)        at ExceptionInterceptor.aroundInvoke(ExceptionInterceptor.java:51)        at sun.reflect.GeneratedMethodAccessor289.invoke(Unknown Source)        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)        at java.lang.reflect.Method.invoke(Method.java:597)        at org.jboss.seam.util.Reflections.invoke(Reflections.java:22)        at org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:187)        at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:72)        at org.jboss.seam.intercept.RootInterceptor.invoke(RootInterceptor.java:107)        at org.jboss.seam.intercept.JavaBeanInterceptor.interceptInvocation(JavaBeanInterceptor.java:185)        at org.jboss.seam.intercept.JavaBeanInterceptor.invoke(JavaBeanInterceptor.java:103)        at TaskService_$$_javassist_seam_7.getNumberOfUpdatedTasks(TaskService_$$_javassist_seam_7.java)        at sun.reflect.GeneratedMethodAccessor319.invoke(Unknown Source)        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)        at java.lang.reflect.Method.invoke(Method.java:597)        at org.jboss.seam.remoting.gwt.GWTToSeamAdapter.callWebRemoteMethod(GWTToSeamAdapter.java:100)        at org.jboss.seam.remoting.gwt.GWTService.RPC_invokeAndEncodeResponse(GWTService.java:550)        at org.jboss.seam.remoting.gwt.GWTService.processCall(GWTService.java:206)        at org.jboss.seam.remoting.gwt.GWTService$1.process(GWTService.java:120)        at org.jboss.seam.servlet.ContextualHttpServletRequest.run(ContextualHttpServletRequest.java:53)        at org.jboss.seam.remoting.gwt.GWTService.getResource(GWTService.java:105)        at org.jboss.seam.servlet.SeamResourceServlet.service(SeamResourceServlet.java:80)        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:83)        at org.jboss.seam.web.LoggingFilter.doFilter(LoggingFilter.java:60)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)        at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:64)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)        at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)        at org.jboss.seam.web.IdentityFilter.doFilter(IdentityFilter.java:40)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:73)        at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158)        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)        at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:235)        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)        at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:190)        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)        at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:92)        at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126)        at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70)        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)        at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)        at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:436)        at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:384)        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)        at java.lang.Thread.run(Thread.java:619)

我们使用 JBoss AS 5.1.0.GA、Seam 2.2.0.GA 和 GWT 2.0.3。 JBoss 通过 mod_jk 接收来自 Apache 2 的请求。提供的行号 (Request.java:2517) 表明请求的方法为 null，尽管 firebug(客户端)、Apache 和 mod_jk 的日志显示该方法为 POST。

目前，我们既不知道 NPE 的根本原因是什么，也不知道如何解决。我们正在推测问题是否与以下有关:

• 垃圾收集(JBoss 以 -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 启动)
• 在 Tomcat 中请求回收
• 在 Tomcat 中过滤链回收
• mod_jk 平衡

我们可以做些什么来找出这个问题的原因？这个问题有什么可能的解决办法吗？

非常感谢任何帮助或建议。

谢谢!

--

我们很幸运，能够在 NPE 期间调试堆栈跟踪。我们发现，MockExternalContext 中的请求对象并不总是与 SeamResourceServlet 接收到的请求对象匹配。有时 MockExternalContext 中的请求对象是新的并且包含 org.apache.coyote.Request 的新实例，所有字段都设置为 null。如果可以处理请求，则SeamResourceServlet收到的请求对象与MockExternalContext中的相同。

任何 Seam 专家都可以帮助我们并告诉我们在上述堆栈中何时何地跟踪 org.jboss.seam.faces.Parameters 使用的 MockExternalContext 是创造？在什么情况下，Seam 会使用新的请求对象而不是 SeamResourceServlet 提供的对象来初始化 MockExternalContext？

我已经在 Seam forum 中交叉发布了这个问题.

--

更新

同时我们找到了 NPE 的原因:

由于我们在客户端使用 GWT，所有客户端-服务器通信都是通过 GWT-RPC 异步完成的。极少数情况下，注销调用会超过另一个仍在处理的 RPC。注销调用使 session 无效，因此其他 RPC 无法正常完成，从而导致在 ServletLifecycle.endRequest(request) 期间出现异常；在 ContextualHttpServletRequest 中。这个异常由 Seam 的 ExceptionFilter 处理。不幸的是，ExceptionFilter 也无法正常完成，因为无效的 Session 导致以下错误:

ERROR    [Seam Resource Servlet].error: Servlet.service() for servlet Seam Resource Servlet threw exceptionjava.lang.IllegalStateException: Cannot create a session after the response has been committed        at org.apache.catalina.connector.Request.doGetSession(Request.java:2338)        at org.apache.catalina.connector.Request.getSession(Request.java:2094)        at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:833)        at javax.servlet.http.HttpServletRequestWrapper.getSession(HttpServletRequestWrapper.java:216)        at org.jboss.seam.mock.MockExternalContext.getSessionMap(MockExternalContext.java:357)        at org.jboss.seam.contexts.FacesLifecycle.beginExceptionRecovery(FacesLifecycle.java:86)        at org.jboss.seam.web.ExceptionFilter.endWebRequestAfterException(ExceptionFilter.java:96)        at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:70)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)        at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)        at org.jboss.seam.web.IdentityFilter.doFilter(IdentityFilter.java:40)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)        at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:73)        at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158)        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)        at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)        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:235)        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)        at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:190)        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)        at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:92)        at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126)        at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70)        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)        at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)        at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:436)        at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:384)        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)        at java.lang.Thread.run(Thread.java:619)

在 ExceptionFilter 中创建的 MockExternalContext，“以某种方式”保留在应用程序上下文中，并且“有时”用于处理请求。它甚至可以在我们的应用程序重新部署后继续存在，因此我们必须重新启动 JBoss 才能摆脱 NPE。

Answer 1

非常感谢这篇文章。这个错误是我们几周的噩梦。我们的配置是:GWT 2.0.4、Seam 2.2.1 CR2、JBoss AS 5.1.0。我们在我们的应用程序中修补了注销机制，但它仍然返回(虽然很少)。现在看来，当事务在 EJB 层中持续时间过长时就会发生这种情况。现在我们准备好摆脱 Seam，它会导致我们无法处理的问题。

更新:当“ServiceImpl”组件的范围从“SESSION”更改(只是删除它)到默认值时，这个奇怪的错误完全消失了。还添加了注释@BypassInterceptors。同时，我为我们的应用程序准备了 Seam-GWT 桥的替代品。这是 Guice + gwt-dispatch。非常快速和可靠的解决方案。