Struts2:java.lang.NoSuchFieldException: resourceEntries at java.lang.Class.getDeclaredField(Class.java:1901)

　　今天在做Struts2的测试用例时候，程序能正常跳转，但是在Console却报了一个错误，如下：

 java.lang.NoSuchFieldException: resourceEntries
     at java.lang.Class.getDeclaredField(Class.java:1901)
     at com.opensymphony.xwork2.util.LocalizedTextUtil.clearMap(LocalizedTextUtil.java:877)
     at com.opensymphony.xwork2.util.LocalizedTextUtil.clearTomcatCache(LocalizedTextUtil.java:857)
     at com.opensymphony.xwork2.util.LocalizedTextUtil.reloadBundles(LocalizedTextUtil.java:841)
     at com.opensymphony.xwork2.util.LocalizedTextUtil.getMessage(LocalizedTextUtil.java:723)
     at com.opensymphony.xwork2.util.LocalizedTextUtil.findMessage(LocalizedTextUtil.java:781)
     at com.opensymphony.xwork2.util.LocalizedTextUtil.findText(LocalizedTextUtil.java:447)
     at com.opensymphony.xwork2.util.LocalizedTextUtil.findText(LocalizedTextUtil.java:374)
     at com.opensymphony.xwork2.TextProviderSupport.getText(TextProviderSupport.java:202)
     at com.opensymphony.xwork2.TextProviderSupport.getText(TextProviderSupport.java:117)
     at com.opensymphony.xwork2.ActionSupport.getText(ActionSupport.java:100)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
     at java.lang.reflect.Method.invoke(Method.java:601)
     at ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:871)
     at ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1273)
     at ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68)
     at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:117)
     at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:101)
     at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1349)
     at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1325)
     at com.opensymphony.xwork2.ognl.accessor.CompoundRootAccessor.callMethod(CompoundRootAccessor.java:232)
     at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1349)
     at ognl.ASTMethod.getValueBody(ASTMethod.java:90)
     at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
     at ognl.SimpleNode.getValue(SimpleNode.java:258)
     at ognl.Ognl.getValue(Ognl.java:494)
     at com.opensymphony.xwork2.ognl.OgnlUtil.getValue(OgnlUtil.java:217)
     at com.opensymphony.xwork2.ognl.OgnlValueStack.getValue(OgnlValueStack.java:342)
     at com.opensymphony.xwork2.ognl.OgnlValueStack.tryFindValue(OgnlValueStack.java:331)
     at com.opensymphony.xwork2.ognl.OgnlValueStack.tryFindValueWhenExpressionIsNotNull(OgnlValueStack.java:307)
     at com.opensymphony.xwork2.ognl.OgnlValueStack.findValue(OgnlValueStack.java:293)
     at org.apache.struts2.components.Property.start(Property.java:162)
     at org.apache.struts2.views.jsp.ComponentTagSupport.doStartTag(ComponentTagSupport.java:53)
     at org.apache.jsp.welcome_jsp._jspx_meth_s_005fproperty_005f0(welcome_jsp.java:227)
     at org.apache.jsp.welcome_jsp._jspService(welcome_jsp.java:129)
     at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
     at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438)
     at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
     at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
     at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
     at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:721)
     at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:466)
     at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:391)
     at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318)
     at org.apache.struts2.dispatcher.ServletDispatcherResult.doExecute(ServletDispatcherResult.java:159)
     at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:186)
     at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:373)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:277)
     at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
     at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263)
     at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
     at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:133)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207)
     at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207)
     at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:142)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:166)
     at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
     at com.opensymphony.xwork2.DefaultActionInvocation.invok
 e(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:190)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
     at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
     at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
     at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:485)
     at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
     at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
     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:106)
     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
     at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
     at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
     at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
     at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2503)
     at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2492)
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
     at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
     at java.lang.Thread.run(Thread.java:722)

　　刚开始，百思不得其解，因为在我的form中没有用到resourceEntries，于是根据代码查看struts2源码，在struts2源码中找到了resourceEntries。

 private static void clearTomcatCache()
   {
     ClassLoader loader = getCurrentThreadContextClassLoader();

     Class cl = loader.getClass();
     try
     {
       if ("org.apache.catalina.loader.WebappClassLoader".equals(cl.getName())) {
         clearMap(cl, loader, "resourceEntries");
       }
       else if (LOG.isDebugEnabled())
         LOG.debug("class loader " + cl.getName() + " is not tomcat loader.", new String[0]);
     }
     catch (NoSuchFieldException nsfe)
     {
       if ("org.apache.catalina.loader.WebappClassLoaderBase".equals(cl.getSuperclass().getName())) {
         if (LOG.isDebugEnabled())
           LOG.debug("Base class #0 doesn't contain '#1' field, trying with parent!", nsfe, new String[] { cl.getName(), "resourceEntries" });
         try
         {
           clearMap(cl.getSuperclass(), loader, "resourceEntries");
         } catch (Exception e) {
           if (LOG.isWarnEnabled())
             LOG.warn("Couldn't clear tomcat cache using #0", e, new String[] { cl.getSuperclass().getName() });
         }
       }
     }
     catch (Exception e) {
       if (LOG.isWarnEnabled())
         LOG.warn("Couldn't clear tomcat cache", e, new String[] { cl.getName() });
     }
   }

　　看到org.apache.catalina.loader.WebappClassLoaderBase好像是tomcat中的问题，于是查看网上资料，发现tomcat8.0的类加载器webappclsaaLoader中没有属性resourceEntries，于是我换了tomcat7.0的看了下，7.0的有属性resourceEntries。看来这个是tomcat版本的问题了。如果需要用tomcat8，这就必须修改struts2的这个bug，再重新编译，这也是开源的一个好处。