spring4mvc 实现文件下载功能reponse.getOutputStream()重复调用问题解决

本来是准备做一个类似网络硬盘的功能，判断目标是文件的时候，点击就启动下载。

谁想遇到了不少麻烦，最直接的麻烦就是遇到了response.getOutputStream()重复使用的异常。。虽然对功能没有影响，但是这个报错的异常始终看着不舒服，百度上搜索了一大圈，总是说什么getWriter()和getOutputStream()只能二选一，因为我采用的是spring4管理，在JSP没有任何jsp代码片段（实际上，就算是我加入了out.clean()两行代码也无效）。

其实很简单，只是自己以前没有用spring框架的时候也遇到过，就是return null；就搞定了。

异常如下

八月 11, 2014 8:33:31 上午 org.apache.catalina.core.StandardWrapperValve invoke严重: Servlet.service() for servlet [xchgx] in context with path [/HbouCn] threw exception [java.lang.IllegalStateException: getOutputStream() has already been called for this response] with root causejava.lang.IllegalStateException: getOutputStream() has already been called for this responseat org.apache.catalina.connector.Response.getWriter(Response.java:636)at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:213)at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:104)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:186)at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:126)at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:80)at org.apache.jsp.WEB_002dINF.views.manager.disk.main_jsp._jspService(main_jsp.java:166)at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:604)at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:543)at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:201)at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:267)at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1221)at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1005)at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:952)at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:745)

出错的代码：

/** * 根据type判断为文件，就启动下载 * @param path 文件名 * @param request * @param response * @throws IOException */@RequestMapping(value="next",method=RequestMethod.GET,params = "type=1")public ModelAndView download(@RequestParam(value="path") String path,HttpServletRequest request,HttpServletResponse response) throws IOException{//这里要转换，不论你是否在tomcat下的server.xml做过修改，还是在JSP中加入response.setCharacter("UTF-8");//或request.....UTF-8都没用，包括spring-servlet.xml和web.xml加入encoding utf-8过滤器都无效，这里一定要加这一句话才能识别中文。<pre name="code" class="java">String nPath = new String(path.getBytes("ISO-8859-1"),"UTF-8");                String parentPath = (String) getSessionObject(request, CommonConstant.CURRENT_DIRECTORY);String filePath = diskService.getNextDirectory(parentPath, nPath);diskService.download(filePath,request,response);return new ModelAndView("manager/disk/main");}

最后决定就加了一句话就搞定了。害我折腾了2天。

/** * 根据type判断为文件，就启动下载 * @param path 文件名 * @param request * @param response * @throws IOException */@RequestMapping(value="next",method=RequestMethod.GET,params = "type=1")public ModelAndView download(@RequestParam(value="path") String path,HttpServletRequest request,HttpServletResponse response) throws IOException{String nPath = new String(path.getBytes("ISO-8859-1"),"UTF-8");String parentPath = (String) getSessionObject(request, CommonConstant.CURRENT_DIRECTORY);String filePath = diskService.getNextDirectory(parentPath, nPath);diskService.download(filePath,request,response);<span style="color:#FF0000;">return null;</span>//妈的原来返回一个null就搞定了response重复调用的问题，害死我了。}

做个笔记，防止忘记