spring-mvc文件下载出现异常：java.lang.IllegalStateException: getOutputStream() has already been called for this response

最近做文件下载的功能，大概就是下载一个excel模板，前端提交表单时，请求后台下载的controller

 

发现后台逻辑结束后，后台出现异常，虽然没有影响文件下载的功能，但考虑到异常有影响程序的运行的风险，所以想办法去除这个异常。

 

异常如下：

 

java.lang.IllegalStateException: getOutputStream() has already been called for this response
    at org.apache.catalina.connector.Response.getWriter(Response.java:564)
    at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:212)
    at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:366)
    at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:283)
    at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:233)
    at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:167)
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250)
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1047)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:817)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at com.airport.common.web.ProcessTimeFilter.doFilter(ProcessTimeFilter.java:35)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:94)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1156)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1539)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1495)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$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)

controller：

    @RequestMapping("/certificate_import/v_download_template.do")
     public String downloadTemplate(HttpServletRequest request,  HttpServletResponse response) {
           log.info("下载证书导入模板...");
           File template =  cmsCertificateImportMng.getCertificateDataTemplate();
           if (template == null) {
                log.warn("没有获取到证书数据导入模板文件，下载失败");
                return "certificate_import/list";
           }
           // 将文件流写入response
           FileDownloadUtils.writeFile2Response(response,  template);
           return "certificate_import/import";
     }

其中FileDownloadUtils.writeFile2Response方法将文件流写入http响应对象中，实现前端的文件下载功能，详细代码实现在这篇博客中：spring-mvc实现文件下载功能

后来我想到，原因可能是前端请求后，后台有两个response响应：

 

第一个response是将文件写到输出流中，第二个是controller返回到原来的页面。

 

最终我找到了解决办法：controller结束后不指定返回的页面，也就是去掉controller的返回值，前端页面将保持不变，只会显示下载的文件。

 

将controller方法改为无返回参数void，修改后的代码：

 

     @RequestMapping("/certificate_import/v_download_template.do")
     public void downloadTemplate(HttpServletRequest request,  HttpServletResponse response) {
           log.info("下载证书导入模板...");
           File template =  cmsCertificateImportMng.getCertificateDataTemplate();
           if (template == null) {
                log.warn("没有获取到证书数据导入模板文件，下载失败");
                return;
           }
           // 将文件流写入response
           FileDownloadUtils.writeFile2Response(response,  template);
     }

 

这样下载时就再没有出现过上述的异常