Spring boot 发送 POST JSON

String post(String xml) throws  Exception{
        // https://juejin.cn/post/6894858380276416525
        RestTemplate restTemplate = new RestTemplate();

        HttpHeaders headers = new HttpHeaders();
//        headers.setContentType(MediaType.TEXT_PLAIN);
        headers.setContentType(MediaType.APPLICATION_JSON);

        Map<String, Object> map = new HashMap<>(16);
        map.put("xml", xml);

        ObjectMapper objectMapper = new ObjectMapper();
        String requestData = objectMapper.writeValueAsString(map);
        HttpEntity<String> request = new HttpEntity<>(requestData, headers);

        ResponseEntity<String> result = restTemplate.postForEntity(noticeMidway(), request, String.class);

        return result.getBody();
    }