java通过url下载文件并输出的方法

controller：
@RequestMapping(value = "/{loanid}/{atmtType}")
 public void doGet(@PathVariable("loanid") String loanid,@PathVariable("atmtType") String atmtType,
   HttpServletRequest req,HttpServletResponse response) {
  Map<String,String> map = new HashMap<String,String>();
  map.put("loanid", loanid);
  Map<String, String> urlByLoanid= new HashMap<String,String>();
 // Map<String, String> urlByLoanid = zcmQueryInfoService.queryUrlByLoanid(map);
  try {
   if(urlByLoanid!=null){
    String wjurl="http://10.0.15.11:8080/gateway//nfs/marvel-core-admin/2017/10/11/compact_seal_17101119371231615_7.pdf";
    //String wjurl = urlByLoanid.get("url");
    int i = wjurl.lastIndexOf("/");
    String fileName = wjurl.substring(i+1);
    
    URL url = new URL(wjurl); 
    HttpURLConnection conn = (HttpURLConnection)url.openConnection(); 
    //设置超时间为3秒 
    conn.setConnectTimeout(3*1000); 
    //防止屏蔽程序抓取而返回403错误 
    conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)"); 
    //得到输入流 
    InputStream inputStream = conn.getInputStream(); 
    //获取自己数组 
    byte[] bs = readInputStream(inputStream); 
    response.setContentType("application/octet-stream;charset=ISO8859-1");
    BufferedOutputStream output = null;
    BufferedInputStream input = null;
     try {
      output = new BufferedOutputStream(response.getOutputStream());
      // 中文文件名必须转码为 ISO8859-1,否则为乱码
      String fileNameDown = new String(fileName.getBytes(), "ISO8859-1");
      // 作为附件下载
      response.setHeader("Content-Disposition", "attachment;filename=" + fileNameDown);
  
      output.write(bs);
      response.flushBuffer();
     } catch (Exception e) {
      log.error("Download log file error", e);
     } // 用户可能取消了下载
     finally {
      if (input != null)
       try {
        input.close();
       } catch (IOException e) {
        e.printStackTrace();
       }
      if (output != null)
       try {
        output.close();
       } catch (IOException e) {
        e.printStackTrace();
       }
     }
   }
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
/** 
  * 从输入流中获取字节数组 
  * @param inputStream 
  * @return 
  * @throws IOException 
  */ 
 public static byte[] readInputStream(InputStream inputStream) throws IOException { 
  byte[] buffer = new byte[1024]; 
  int len = 0; 
  ByteArrayOutputStream bos = new ByteArrayOutputStream(); 
  while((len = inputStream.read(buffer)) != -1) { 
   bos.write(buffer, 0, len); 
  } 
  bos.close(); 
  return bos.toByteArray(); 
 }