code: public static String post(String url, Map<String, String> queryParas, String data, Map<String, String> headers) {
  		HttpURLConnection conn = null;
  		try {
  			conn = getHttpConnection(buildUrlWithQueryString(url, queryParas), POST, headers);
  			conn.connect();
  			
  			OutputStream out = conn.getOutputStream();
  			out.write(data != null ? data.getBytes(CHARSET) : null);
  			out.flush();
  			out.close();
  			
  			return readResponseString(conn);
  		}
  		catch (Exception e) {
  			throw new RuntimeException(e);
  		}
  		finally {
  			if (conn != null) {
  				conn.disconnect();
  			}
  		}
  	}
docs: Send POST request