/**
     * 向目的URL发送post请求
     * @param url       目的url
     * @param params    发送的参数
     * @return  ResultVO
     */
    public static ResultVO sendPostRequest(String url, MultiValueMap<String, String> params){
        RestTemplate client = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        HttpMethod method = HttpMethod.POST;
        // 以表单的方式提交
        headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
        //将请求头部和参数合成一个请求
        HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<>(params, headers);
        //执行HTTP请求，将返回的结构使用ResultVO类格式化
        ResponseEntity<ResultVO> response = client.exchange(url, method, requestEntity, ResultVO.class);

        return response.getBody();
    }