Why do not I get the id when mapping from DTO to entity with mapstruct? - spring-boot

Question

I have an API with spring boot and I use mapstruct and I just want to update the Person entity. For this, having PersonDto update Person.
What I have so far:
Mapper:
#Mapper
public interface PersonMapper {
PersonDto toPersonDto(Person person);
Person toPerson(PersonDto personDto);
Person updatePersonFromDto(PersonDto persoonDto, #MappingTarget
Person document);
}
In service layer:
Find Person:
public PersonDto updatePerson(Long personId) {
PersonDto personDto = personService.findById(personId)
.orElseThrow(() -> new PersonNotFoundException(id));
personDto.set(...) //set others properties
Person person = personMapper.toPerson(personDto);
person = personMapper.updatePersonFromDto(personDto, person);
personRepository.save(person);
return personMapper.toPersonDto(person);
}`
My question, is there a strategy or a better way of update an entity from a DTO?
Edit:
I was able to solve a part, now I do not lose the id, but I still create a new object instead of updating it. The id is in AbstractPersistableEntity.
#Entity
#Getter
#Setter
#Builder
#AllArgsConstructor
#NoArgsConstructor
public class Person extends AbstractPersistableEntity<ID> implements Serializable {
#Column
private String name;
#Column
private String lastName;
#Column
private Integer age;
}
public class PersonDto {
#JsonProperty(access = JsonProperty.Access.READ_ONLY)
private Long id;
private String name;
private String lastName;
private Integer age;
}

Answer 1

Maybe it is not the most optimal or correct solution but it works. I made the following modifications to the mapper:
#BeanMapping(nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE,
nullValueCheckStrategy = NullValueCheckStrategy.ALWAYS)
Person updatePersonFromDto(PersonDto persoonDto, #MappingTarget
Person document);
#ObjectFactory
default Person updatePerson(PersonDto personDto, Person person){
if (personDto != null){
Long id = person.getId();
Person resultPerson = updatePersonFromDto(personDto, person);
resultPerson.setId(id);
return resultPerson;
}
return null;
}
Then from the service just call:
person = personMapper.updatePerson(personDto, person);