我有一个名为 GetFile 的操作，它直接打开一个文件下载框来打开 PDF。
下面是 struts.xml 配置和相同的操作类。我使用结果类型作为流来实现这一点。我可以看到 pdf 下载框一直打开，我也可以下载文件。
但我发现昨晚有一些请求触发了该操作，并产生了以下错误。
org.apache.jasper.JasperException: java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:570)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:452)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:391)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:593)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:530)
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:374)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:278)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at deshaw.irweb.web.interceptor.AuthInterceptor.intercept(AuthInterceptor.java:60)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:510)
at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:434)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:498)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:394)
at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:294)
at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:183)
at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:169)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:636)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:205)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:105)
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:182)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:123)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:80)
at org.apache.jsp.jsp.ServerError_jsp._jspService(ServerError_jsp.java:157)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
... 38 more
有人可以告诉我可能导致问题的原因吗？我目前无法重现该问题。我在某处读到这可能是由于关闭了下载对话框，但即使在我从多个浏览器尝试之后也不是这样。还检查了getOutputStream() 已为此响应调用，但无法直接与我的问题相关，因为没有重定向到 jsp，因为 struts2 操作直接导致结果流。
struts.xml
<action name="GetFile" class="Class" method="DownloadFile">
<result name="success" type="stream">
<param name="contentType">contentType</param>
<param name="contentDisposition">fileName</param>
<param name="bufferSize">1024</param>
<param name="inputName">inputStream</param>
</result>
</action>
动作类
public String DownloadFile ()
{
// create the object variable pdfdoc which is a custom object.
// You can assume that the pdfdoc is properly constructed
// and getFileContent does what it is required to do, so
// that the final pdf is generated.
...
...
inputStream = new ByteArrayInputStream(pdfdoc.getFileContent());
contentType = pdfdoc.getContentType();
fileName = pdfdoc.getFileName();
contentDisposition = doc.getContentDisposition();
bufferSize = 1024;
return "success";
}