两种形式无非一个是放在body里面，一个是以问号拼接放在链接后面

raw形式(body里面)

 RestTemplate restTemplate = new RestTemplate();
 
 //请求头
 HttpHeaders requestHeaders = new HttpHeaders();
        requestHeaders.add("Content-Type", "application/json; charset=UTF-8");
		//参数
        Map map =  new HashMap<String, String>();
        //或
      //   MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
      //HttpEntity<MultiValueMap<String, Object>> httpEntity = new HttpEntity<>(map , requestHeaders);
        
        HttpEntity httpEntity = new HttpEntity<>(map, requestHeaders);
        ResponseEntity<Map> response2 = restTemplate.postForEntity("url", httpEntity, Map.class);

Params形式(问号拼接)

 HttpHeaders requestHeaders = new HttpHeaders();
         requestHeaders.add("Content-Type", "application/json; charset=UTF-8");
        MultiValueMap<String, Object> params = new LinkedMultiValueMap<>();
        UriComponents uriComponents = UriComponentsBuilder.fromUriString("http://base-auth/auth/oauth/token")
                .queryParam("username", username).queryParam("password", password)
                .build();
        URI uri = uriComponents.toUri();
        HttpEntity<MultiValueMap<String, Object>> httpEntity = new HttpEntity<>(params, requestHeaders);
        RestTemplate restTemplate = new RestTemplate();
        return restTemplate.postForObject(uri, httpEntity, Map.class);