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Struts Action 类的 execute() 方法…返回 null

我正在研究“Struts 1 插件”。

我们有一个 Struts1 应用程序，我们想使用 Struts1 应用程序的 Action、ActionForm 进入 Struts 2 应用程序。

在 Struts 1 插件中，所有的 Action 类都是从 Struts1Action 类中调用的。

 public class Abc extends Action
    {
            public ActionForward execute(mapping, form, request, response)
            {
                if(some conditon)
                {
                    response.sendRedirect("/some/action.do");
                    return null;
                }
            }
    }

上面的代码在“Struts 1”中运行良好，但是当我尝试使用“Struts 1 Plugin”时，我抛出了一个错误。

org.apache.catalina.core.StandradWrapperValve 调用服务器：Servlet.service() for servlet 默认在 ResponseFacade.sendError(java: 704) 处抛出异常 java.lang.IllegalStateException；在 javax.servlet.http.HttpServletResponseWrapper.sendError(java:108);

原因在Struts1Action课堂上，

if (forward instanceof WrapperActionForward ||
actionConfig.getResults().containsKey(forward.getName())) {

上面的行抛出错误。

评论中的问题，有答案：

null从您当前的环境中返回是否合法？

是的，退货是合法的null。

真的forward是一个实例WrapperActionForward吗？

是Forward的一个实例WrapperActionForward。

或者，是actionConfig.getResults().containsKey(forward.getName()) true吗？返回什么forward.getName()？

当forwardis时null，actionConfig.getResults().containsKey(forward.getName())会抛出空指针异常。

这是堆栈跟踪：

Feb 21, 2012 4:21:22 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet default threw exception
java.lang.IllegalStateException
at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:407)
at javax.servlet.http.HttpServletResponseWrapper.sendError(HttpServletResponseWrapper.java:108)
at org.apache.struts2.dispatcher.Dispatcher.sendError(Dispatcher.java:839)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:533)
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:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at aaa.bbb.ccc.ddd.eee.DisableUrlJSessionIdFilter.doFilter(DisableUrlJSessionIdFilter.java:65)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at aaa.bbb.ccc.ddd.eee.SetUIComponentsFilter.doFilter(SetUIComponentsFilter.java:390)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at aaa.bbb.ccc.ddd.eee.CrossSiteScriptingFilter.doFilter(CrossSiteScriptingFilter.java:44)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at aaa.bbb.ccc.ddd.eee.PerformanceFilter.doFilter(PerformanceFilter.java:66)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at aaa.bbb.ccc.ddd.eee.AppContextFilter.doFilter(AppContextFilter.java:61)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at aaa.bbb.ccc.ddd.eee.ProfileFilter.doFilter(ProfileFilter.java:56)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:264)
at org.acegisecurity.intercept.web.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:107)
at org.acegisecurity.intercept.web.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:72)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:110)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:217)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
at org.acegisecurity.wrapper.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:81)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:229)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
at org.acegisecurity.util.FilterChainProxy.doFilter(FilterChainProxy.java:148)
at org.acegisecurity.util.FilterToBeanProxy.doFilter(FilterToBeanProxy.java:98)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:291)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:662)
4

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