String imgUrl="";//图片地址
    try {
      // 构造URL
      URL url = new URL(imgUrl);
      // 打开连接
      URLConnection con = url.openConnection();
      // 输入流
      InputStream is = con.getInputStream();
      // 1K的数据缓冲
      byte[] bs = new byte[1024];
      // 读取到的数据长度
      int len;
      // 输出的文件流
      OutputStream os = new FileOutputStream("c:\\image.jpg");//保存路径
      // 开始读取
      while ((len = is.read(bs)) != -1) {
        os.write(bs, 0, len);
      }
      // 完毕，关闭所有链接
      os.close();
      is.close();
    } catch (MalformedURLException e) {
      e.printStackTrace();
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }

String imgUrl="";//URL地址
    String fileName = imgUrl.substring(imgUrl.lastIndexOf('/') + 1);
    BufferedInputStream is = null;
    BufferedOutputStream os = null;
    try {
      URL url = new URL(imgUrl);
      this.getServletResponse().setContentType("application/x-msdownload;"); 
      this.getServletResponse().setHeader("Content-disposition", "attachment; filename=" + new String(fileName.getBytes("utf-8"), "ISO8859-1")); 
      this.getServletResponse().setHeader("Content-Length", String.valueOf(url.openConnection().getContentLength()));      
      is = new BufferedInputStream(url.openStream());
      os = new BufferedOutputStream(this.getServletResponse().getOutputStream()); 
      byte[] buff = new byte[2048]; 
      int bytesRead; 
      while (-1 != (bytesRead = is.read(buff, 0, buff.length))) { 
        os.write(buff, 0, bytesRead); 
      } 
      if (is != null) 
        is.close(); 
      if (os != null) 
        os.close();
    } catch (MalformedURLException e) {
      e.printStackTrace();
    } catch (UnsupportedEncodingException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }