@Mapper
public abstract class PersonMapper {

   @Mapping(source = "id", target = "personId.id")
   public abstract Person personFromDto(PersonDto person);

   @InheritInverseConfiguration()
   public abstract PersonDto personToDto(Person person);

   // <1>
   public PersonId.Builder personIdBuilder() {
      return new PersonId.Builder();
   }
}

public class PersonId {
   private final Integer id;

   public PersonId(Integer id) {
      this.id = id;
   }
  
  // <2>
  public static Builder builder() {
      return new Builder();
   }

   public static class Builder {
      private Integer id;

      public Builder setId(Integer thatId) {
         this.id = thatId;
         return this;
      }

      public PersonId build() {
         return new PersonId(this.id);
      }
   }