struts2下载的问题

突然出现这个错误，其实是返回的inputstream是null 。可以看后台的代码，可能使数据库什么的有异常。单独执行下后台代码可以定位错误
java.lang.IllegalArgumentException: Can not find a java.io.InputStream with the name [excelStream] in the invocation stack. Check the <param name="inputName"> tag specified for this action.

    org.apache.struts2.dispatcher.StreamResult.doExecute(StreamResult.java:237)    org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:191)    com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:372)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:276)    org.apache.struts2.interceptor.DeprecationInterceptor.intercept(DeprecationInterceptor.java:41)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:168)    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:76)    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229)    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229)    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:125)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:253)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:140)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189)    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:567)    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:81)    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)    org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)    org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)    org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)    org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)    org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)    org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)    java.lang.Thread.run(Thread.java:619)