request.setCharacterEncoding("utf-8");

         String name=request.getParameter("name");

         //1、设置响应头

         response.setContentType("application/force-download");

         //2、读取文件

         String path=getServletContext().getRealPath("/file/"+name);

         InputStream in=new FileInputStream(path);

         //3、对文件名进行编码

         name=URLEncoder.encode(name, "utf-8");

         //4、设置响应头

         response.setHeader("Content-Disposition","attachment;filename="+name);//如果不写attachment，则会在浏览器中打开

         response.setContentLength(in.available());

         //5、开始copy文件

         OutputStream out=response.getOutputStream();

         byte[] b=new byte[1024];

         int len=-1;

         while((len=in.read(b))!=-1)

         {

             out.write(b, 0, len);

         }

         out.close();

         in.close();

     }