http Post 请求一网络资源返回字符串

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;
 }