Question

This is not the first time that I’ve found myself in a situation in which I have to adapt two objects with almost the same data, for example:

User.java  (Object returned from another library)
private String name;
private String surname;
private String email;
private String telephone;
...
getters and setters();
constructor();

---

MyUser.java
private String name;
private String surname;
private String email;
private String telephone;
...
getters and setters();
constructor();

I usually create a method to convert one object into another one, like this:

 User m1 = new User();
 MyUser m2 = new MyUser();
 m2.setName(m1.getName());
 m2.setsurmame(m1.getsurname());

…and so on…

Does anybody know a different way to do this kind of stuff?

Answer 1

Use Object Composition For objects that you create using the other library, create an instance of ExternalUser. But if you want to create them locally, create a BrandNewUser. Then you can just treat them the same way, with one version using the pass-through composition methods, and the ones created by your code using your own internal implementation.

You can create your object like this:

public interface MyUser {
  // all the methods you need
  String getSurname();
}

public class ExternalUser implements MyUser {
  private User _user;
  private ExternalUser() { }
  public ExternalUser(User u) {
    this._user = u;
  }
  public String getSurname() {
    return _user.getSurname();
  }
}

public class BrandNewUser implements MyUser {
  private String _surname;
  public ExternalUser(String name, String surname) {
    this._surname = surname;
  }
  public String getSurname() {
    return _surname;
  }
}