HMAC Validation in SpringBoot failing due to rearrangement of JSON

I am trying to have HMAC in springBoot for REST API. The request I send from Postman is

{
    "name":"xyz",
    "description":"hello world",
    "phone":"123456",
    "id":"1"
}

it reached my controller and then to the service where I have a function to validate HMAC. In the controller I pass the signature as the header and payload in the requestBody

@RestController
public class UserController {
    
    
    @Autowired
    UserInterface userInterface;
    
    @PostMapping(value = "/" ,consumes = MediaType.APPLICATION_JSON_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
    public void createUser(@RequestBody User user, @RequestHeader Map<String, String> headers) {
        userInterface.hmacValidation(user, headers);
    }

}

@Service
public class UserService  implements UserInterface {
    public void hmacValidation(User requestBody, Map<String, String> header) {
        var headerSignature = header.get("signature");
        var payload = getRequestBodyAsString(requestBody);
        String result = Hashing.hmacSha256("12345".getBytes(StandardCharsets.UTF_8)).hashString(payload,StandardCharsets.UTF_8).toString();
        
    }
    
    private String getRequestBodyAsString(User requestBody) {

        var mapper = new ObjectMapper();
        String payload = null;
        try {
            mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
            payload = mapper.writeValueAsString(requestBody);
            } catch (JsonProcessingException e) {
        }
        return payload;
    }
}

here from the getRequestBodyAsString(User requestbody) function the output I get is a shuffled/rearranged JSON request which generates different Signature which then mismatches the signature client is sending.

the payload that is converted back from UserObject:

{"name":"xyz","id":"1","description":"hello world","phone":"123456"}

public class User {
    
    private String name;
    private String id;
    private String description;
    private String phone;
}   

The client can send the request in any order but I have to validate signature regardless of the order the request comes in

Is there any other way to validate HMAC?