java 实现对指定目录的文件进行下载

      @RequestMapping("/exportDocument")
      @ResponseBody
      public void exportDocument(HttpServletRequest request,HttpServletResponse response) throws IOException {
         XWPFDocument xdoc = null;
         FileInputStream is = null;
         OutputStream out=null;
         try {
             String wordName="数聚空港2.0使用手册.docx";
             wordName = new String(wordName.getBytes(), "iso8859-1");
             // File file = new File("/root/usersGuide.docx");
             response.setContentType("APPLICATION/OCTET-STREAM");
             response.setHeader("Content-Disposition", "attachment; filename="+ wordName);
             is = new FileInputStream("/root/usersGuide.docx");
             out=response.getOutputStream();//获得一个output对象
             xdoc = new XWPFDocument(is);
             } catch (IOException e) {
                 e.printStackTrace();
             }finally{
                 try {
                     xdoc.write(out);//Write out this document to an Outputstream.
                     is.close();
                     out.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
             /*上述是word文档的下载*/

             /*下面是对各种类型的文件下载*/

                  /*
 　　
 　　　　　　　　　　//2.获取要下载的文件名
                 String fileName = "test.png";
                 //3.设置content-disposition响应头控制浏览器以下载的形式打开文件
                 response.setHeader("content-disposition", "attachment;filename="+fileName);
                 //4.获取要下载的文件输入流
                 InputStream in=null;
                 OutputStream out=null;
                 try {//获取要下载的文件的绝对路径
                     in=new FileInputStream("/root/运营线路图0.3.5版.png");
                     int len = 0;
                      //5.创建数据缓冲区
                      byte[] buffer = new byte[1024];
                      //6.通过response对象获取OutputStream流
                      out = response.getOutputStream();
                      //7.将FileInputStream流写入到buffer缓冲区
                      while ((len = in.read(buffer)) > 0) {//in.read(byte[] b)最多读入b.length个字节 在碰到流的结尾时 返回-1
                      //8.使用OutputStream将缓冲区的数据输出到客户端浏览器
                          out.write(buffer,0,len);
                      }
                  }catch (FileNotFoundException e) {
                     e.printStackTrace();
                  }finally{
                      in.close();
                      out.close();
                  }*/
     }