我在做一个spring boot项目。我想从请求对象中删除空属性。这是因为在下一步中，我需要将请求对象传递给第三方api，而不使用null属性。我在网上搜索了一下，发现我可以使用jsoninclude.include.non\u null。但是对象仍然有空值。下面是我的示例代码，
模型，

@JsonInclude(JsonInclude.Include.NON_NULL)
public class RequestTest {
    private String firstname;
    private String lastname;
    private Integer age;

    public String getFirstname() {
        return firstname;
    }
    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }
    public String getLastname() {
        return lastname;
    }
    public void setLastname(String lastname) {
        this.lastname = lastname;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
}

控制器，

@PostMapping("/test/person")
public String testPerson(@RequestBody RequestTest req){
    log.info(gson.toJson(req)); //I need to pass this to 3rd party API without null fields.
    return "success";
}

这是我从日志里得到的，

{
  "firstname": "foo",
  "lastname": null,
  "age": 15
}

对象仍包含空值。请帮忙。
编辑
这是我需要将对象传递给第三方api的示例代码，

public String passToThirdParty(RequestTest req){
    RestTemplate restTemplate = new RestTemplate();

    String url = "/xxx";

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

    HttpEntity<RequestTest> entity = new HttpEntity<>( req, headers);

    log.info(gson.toJson(entity)); //Inside body, it still has "lastname": null.

    ResponseEntity<String> result = restTemplate.exchange(url, HttpMethod.POST, entity, String.class);

    return result.getBody();
}

在实体的日志主体中，仍然有“lastname”：null请帮助。还是需要逐个字段手动删除？