How to not return null value in ResponseEntity?

I use ResponseEntity to return response for a GET "api/v1/name" and POST "api/v1/name" request.

My goal is not to return response with null value, for example in a POST "api/v1/name" request, currently the response body would be:

{
    "id": null,
    "name": "who",
    "newid": "A8C90A53-78F6-4BD6-9628-CBA8FC349C08"
}

What I wish it would look like:

{
    "name": "who",
    "newid": "A8C90A53-78F6-4BD6-9628-CBA8FC349C08"
}

In my opinion, recreating the object using this code below would only make the code less readable and maybe use more memory (I am not sure, please let me know if I am wrong):

...
Map<String, String> responseBody = new HashMap<>();
responseBody.put("name", nameModel.getName());
responseBody.put("newid", nameModel.getNewId());

return new ResponseEntity<>(responseBody, HttpStatus.OK);

==== Down below is the full repository, if you wish to see the updated one: https://github.com/kidfrom/g2_java/tree/main/etc/mssqlserver

controller/NameController.java

package com.example.mssqlserver.controller;

import com.example.mssqlserver.mapper.NameMapper;
import com.example.mssqlserver.model.NameModel;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

@RestController
public class NameController {

  @Autowired
  private NameMapper nameMapper;

  @GetMapping("api/v1/name")
  public ResponseEntity<?> selectAll() {
    return new ResponseEntity<>(nameMapper.selectAll(), HttpStatus.OK);
  }

  @PostMapping("api/v1/name")
  public ResponseEntity<?> insert(@RequestBody NameModel nameModel) {

    // validator
    if (!nameModel.requestIsValid()) {
      return ResponseEntity.badRequest().build();
    }

    if (nameMapper.insert(nameModel) == 1) {
      return new ResponseEntity<>(nameModel, HttpStatus.OK);
    } else {
      return ResponseEntity.badRequest().build();
    }
  }
}

mapper/NameMapper.java

package com.example.mssqlserver.mapper;

import com.example.mssqlserver.model.NameModel;
import org.apache.ibatis.annotations.*;

import java.util.List;

@Mapper
public interface NameMapper {

  @Select("SELECT * FROM name")
  public List<NameModel> selectAll();

  @SelectKey(statement = "SELECT NEWID()", keyProperty = "newid", resultType = String.class, before = true)
  @Insert("INSERT INTO name (name, newid) VALUES (#{name}, #{newid})")
//  @Options(useGeneratedKeys = true, keyProperty = "id")
  int insert(NameModel nameModel);
}

model/NameModel.java

package com.example.mssqlserver.model;

public class NameModel {
  private Integer id;
  private String name;
  private String newid;

  public NameModel(Integer id, String name, String newid) {
    this.id = id;
    this.name = name;
    this.newid = newid;
  }

  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public String getNewid() {
    return newid;
  }

  public void setNewid(String newid) {
    this.newid = newid;
  }

  public boolean requestIsValid() {
    if (this.name.isEmpty()) return false;

    return true;
  }
}