PersonMapper

public class PersonMapper implements Mapper<PersonDTO, Person> {

    public Person map(PersonDTO dto) {
        Person person = null;
        if (person.type.equals("Student")) {
            person = new Student(dto.gpa);
        } else if (person.type.equals("Employee")) {
            person = new Employee(dto.startDate);
        }
        setupCommonFields(person, dto);
        return person;
    }

    private void setupCommonFields(Person person, PersonDTO dto) {
        person.id = dto.id;
        person.name = dto.name;
    }
}