public static String sendPost(String url, String param) {

  PrintWriter out = null;

  BufferedReader in = null;

  String result = "";

  try {

   URL realUrl = new URL(url);

   // 打开和URL之间的连接

   URLConnection conn = realUrl.openConnection();

   // 设置通用的请求属性

   conn.setRequestProperty("accept", "*/*");

   conn.setRequestProperty("connection", "Keep-Alive");

   // 发送POST请求必须设置如下两行

   conn.setDoOutput(true);

   conn.setDoInput(true);

   // 获取URLConnection对象对应的输出流

   out = new PrintWriter(conn.getOutputStream());

   // 发送请求参数

   out.print(param);

   // flush输出流的缓冲

   out.flush();

   // 定义BufferedReader输入流来读取URL的响应

   in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));

   String line;

   while ((line = in.readLine()) != null) {

    result += line;

   }

  } catch (Exception e) {

   System.out.println("发送 POST 请求出现异常！" + e);

   e.printStackTrace();

  }

  // 使用finally块来关闭输出流、输入流

  finally {

   try {

    if (out != null) {

     out.close();

    }

    if (in != null) {

     in.close();

    }

   } catch (IOException ex) {

    ex.printStackTrace();

   }

  }

  return result;

 }