错误信息如下：
400错误请求：[未识别的字段“rep”（class org.keydrope.representations.idm.userrepresentation），未标记为可忽略]
下面是一些代码：

public String createUser2() throws UnsupportedEncodingException, JSONException {

    String adminToken = getAccessToken();

    System.out.println("token: " + adminToken);

    HttpHeaders headers = new HttpHeaders();
    headers.set("Content-Type", "application/json");
    headers.set("Authorization", "Bearer " + adminToken);

    UserRepresentation userRepresentation = new UserRepresentation();
    userRepresentation.setFirstName("some");
    userRepresentation.setLastName("user");
    userRepresentation.setUsername("Some.User@somewhere.com");
    userRepresentation.setEmail("Some.User@somewhere.com");

//gson gson=新gson（）；//string jsonstring=gson.tojson（用户表示）；

MultiValueMap<String, UserRepresentation> map = new LinkedMultiValueMap<String, UserRepresentation>();
    map.add("rep", userRepresentation);

    HttpEntity<MultiValueMap<String, UserRepresentation>> request = new HttpEntity<>(map, headers);

    String uri = "http://10.127.2.46:31680/auth/admin/realms/12xDemo/users";
    System.out.println("URI: " + uri);

    UserRepresentation response = (new RestTemplate()).postForObject(uri, request, UserRepresentation.class);
    //JSONObject obj = new JSONObject(response);

    return (new Gson()).toJson(response);
}