how can it solve correct converting to map from vo object in spring?

Question

parameter VO in spring

public class Person {
  private String name;
  private int age;
  private String job;

    public void setName(String name){
       this.name = name;
    }
    public String getName(){
      return this.name;
    }

    public void setAge(int age){
       this.age= age;
    }
    public int getAge(){
      return this.age;
    }

    public void setJob(String job){
       this.job= job;
    }
    public String getJob(){
      return this.job;
    }

}

@Data
public class Developer extends Person{
  private String lanaguage;
  private int experience;
  private List<Project> projects;
}

@Data
public class Project {
 private String title;
 private String period;
 private String description;
 private String framework;
 private String memmonth;
}

JS

let params = {};
params.language = 'java';
params.experience = '10';
params.projects = [
 {title: 'first-project', period: 1, description: 'operation', framework: 'N', memmonth: '3/1'}
,{title: 'second-project', period: 2, description: 'admin', framework: 'N', memmonth: '3/1'}
]

$.ajax({
   contentType: 'application/json; charset=UTF-8'
   , url: '/hr/insert/'
   , data: JSON.stringify(param)
   , type: 'POST'
   , dataType: 'JSON'
   , success: function (result) {
     console.log(result);
   }
   , error: function(xhr) {}
});

Controller

@Controller
public class HumanResourceController {
    private static final Logger logger = LoggerFactory.getLogger(HumanResource.class);
    @Autowired
    private ResponseEntity<?> HrServivceImple hrServiveImpl;

   // hr insert
   @RequestMapping(value="/hr/insert", method=RequestMethod.POST, produce="application/json;charaset=utf-8")
   @ResponseBody
   public ResponseEntity<?> insertResource(@RequestBody Developer params) {
      // jackson library
      ObjectMapper ob = new ObjectMapper();
      // try object to map convert
      logger.info("convert param {}", ob.convertValue(param, Map.class));
      return hrServiceImpl.insert(params);
   }

   // hr update
   @RequestMapping(value="/hr/update", method=RequestMethod.POST, produce="application/json;charaset=utf-8")
   @ResponseBody
   public ResponseEntity<?> updateResource(@RequestBody Developer params) {
      // jackson library
      ObjectMapper ob = new ObjectMapper();
      // try object to map convert
      logger.info("convert param {}", ob.convertValue(param, Map.class));
      // update hr
      return hrServiceImpl.update(params);
   }

   // hr delete
   @RequestMapping(value="/hr/delete", method=RequestMethod.POST, produce="application/json;charaset=utf-8")
   @ResponseBody
   public ResponseEntity<?> updateResource(@RequestBody Developer params) {
      // jackson library
      ObjectMapper ob = new ObjectMapper();
      // try object to map convert
      logger.info("convert param {}", ob.convertValue(param, Map.class));
      // delete hr
      return hrServiceImpl.delete(params);
   }


}

Log that convert vo to map in contrlloer side

  {
       language=java
     , experience=10
     , projects=[
        {
           name=null
          , age=0
          , job=null
          , title=first-project
          , period=1
          , description=operation
          , framework=N
          , memmonth=3/1
        }
        , {
           name=null
          , age=0
          , job=null
          , title=second-project
          , period=2
          , description=admin
          , framework=N
          , memmonth=3/1
       }
      ]
    }

I was tried it code in spring. but I checked convert VO format that combined with variable in super class by using Jackson library. Why can it be included variable in super class to "proejcts" variable List? I want to get below it format

JSON format
    {
       language=java
     , experience=10
     , projects=[
        {
           title=first-project
          , period=1
          , description=operation
          , framework=N
          , memmonth=3/1
        }
        , {
          , title=second-project
          , period=2
          , description=admin
          , framework=N
          , memmonth=3/1
       }
      ]
       , name=null
       , age=0
       , job=null
    }