protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       String path = this.getServletContext().getRealPath("/download/番茄.png");
       String filename = path.substring(path.lastIndexOf("/") + 1);
       //关键地方,URLencode,不然不能下载中文名称的文件
       response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(filename, "UTF-8"));

       FileInputStream inputStream = new FileInputStream(path);
       ServletOutputStream outputStream = response.getOutputStream();
       byte[] buffer = new byte[1024];
       int len = 0;
       while ((len = inputStream.read(buffer)) > 0) {
           outputStream.write(buffer, 0, len);
       }
       inputStream.close();
   }