Data Layer, Model Layer and interfaces in Java

Question

Lets say we wish to represent a Person

public interface Person {

    String getFirstName();

    String getLastName();

}

This is implemented with JPA (code I am missing out since it is pretty banal)

Now, I wish to have a Model, the interface of which is an extension of the person interface with setter methods

public interface PersonModel extends Person {

    void setFirstName(String firstName);

    void setLastName(String lastName);

}

and I implement a concrete implementation of the Model interface (which I am skipping since its pretty banal again)

In doing this I realised that the PersonModel extending from Person doesn't really make that much sense since a "PersonModel is not a Person"

It is also not "correct" to cast a PersonModel to Person.

What is the correct way to implement this - PersonModel could just not inherit from Person and re-define the methods but that means extra maintenance.

I could extract the methods to another base interface -> PersonBase(?) and extend both Person (no other methods defined) and PersonModel from that.

If I am going down the above path, what would be the best way to name the base interface?

One of the main reasons I am using interfaces (apart from the fact that it helps me in thinking through about how everything would work / fit together) is so that there can easily be different implementation layers (JPA2/NoSQL Driver etc.)

This is not real code being used, so please excuse any syntax errors / typos - I just wrote it up for the purpose of this question.

Thoughts / guidance / advice appreciated.

Answer 1

Upcasting seems to work fine:

package person;

public class PersonApp {
    public static void main(String [] args)
    {
        ConcretePerson p = new ConcretePerson("Superman");
        System.out.println(p.getName());
        PersonModel pm= p;
        System.out.println(pm.getName());
        Person pn=p;
        System.out.println(pn.getName());
        Person pnm=pm;
        System.out.println(pnm.getName());
    }
}

program output:

Superman
Superman
Superman
Superman