java.lang.IllegalStateException：已为此响应调用getWriter（）

Question

嗨，我正在尝试从Web服务下载文件，我从服务获取文件，但是在获取Servlet响应编写器的行上出现异常，并且不知道是什么引起了问题。

private void downloadFile(HttpServletRequest request, HttpServletResponse response) {
        ServletOutputStream servletStream;
        try {
            if (fileImpl == null) {
                fileImpl = new FileHandlerImplService();
            }
            if (service == null) {
                service = fileImpl.getFileHandlerImplPort(new MTOMFeature());
            }
            String fileName = request.getParameter("fileName");
            byte[] data = service.downloadFile(fileName,
                    request.getSession().getAttribute("user").toString().trim());
            File file = new File(fileName);
            OutputStream outStream = new FileOutputStream(file);
            BufferedOutputStream bufferStream = new BufferedOutputStream(outStream);
            bufferStream.write(data);
            bufferStream.close();

            String mimeType = getServletContext().getMimeType(file.getAbsolutePath());
            response.setContentType(mimeType != null ? mimeType : "application/octet-stream");
            response.setContentLength((int) file.length());
            response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
            InputStream inputStream = new FileInputStream(file);
            servletStream = response.getOutputStream();
            byte[] bufferData = new byte[1024*1024];
            int read = 0;
            while ((read = inputStream.read(bufferData)) != -1) {
                servletStream.write(bufferData, 0, read);
            }
            servletStream.flush();
            servletStream.close();
            inputStream.close();
            file.deleteOnExit();
            response.sendRedirect("downloadFile.jsp");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

这是我得到的例外

severe:   java.lang.IllegalStateException: getWriter() has already been called for this response
    at org.apache.catalina.connector.Response.getOutputStream(Response.java:746)
    at org.apache.catalina.connector.ResponseFacade.getOutputStream(ResponseFacade.java:206)
    at servlets.FileRequestHandler.downloadFile(FileRequestHandler.java:90)
    at servlets.FileRequestHandler.processRequest(FileRequestHandler.java:58)
    at servlets.FileRequestHandler.doPost(FileRequestHandler.java:200)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
    at java.lang.Thread.run(Thread.java:744)
Info:   visiting unvisited references
Info:   visiting unvisited references
Info:   visiting unvisited references
Info:   Loading application [JigarJoshiWebClient] at [/JigarJoshiWebClient]
Info:   JigarJoshiWebClient was successfully deployed in 481 milliseconds.

Answer 1

您实际上应该将数据逻辑从Servlet移到DataAccessLayer。

http://tomcat.apache.org/tomcat-5.5-doc/servletapi/javax/servlet/ServletResponse.html

Answer 2

我认为您收到IllegalStateException的原因是因为您在提交输出（即在执行flush（）之后）之后调用response.sendRedirect（）。

您可以删除response.sendRedirect（）行并尝试运行该应用程序。 它应该工作！