Different methods need different attributes in one object

Question

I have a given web service. (This is only an example, the real one is more complex, but it has the same problem.) The service has three methods and all three methods have a person as parameter and need other things from it. (I can't change the entity or methods.)

Entity (Person) (It has only a default constructor):

private String name;
private int age;
private Address address;
private List<String> hobbies;
private List<Person> friends;

• Method1 needs name and age.
• Method2 needs address name and age.
• Method3 needs all.

I need to fill the object from my own objects. I need to write a "converter". What is the best practice for it?

My solutions:

• Builder Pattern with builds for three methods.
• Set all attributes and send unhandled overhead (bad solution in my eyes).

Answer 1

1. Creating a builder that sets only required fields sounds good.

2. You can inherit from this class for each of your needs and implement your own constructors

   public class Target {
       // fields
   }
   
   public class Purpose1 extends Target {
       public Purpose1(String name, int age) {
           // set fields or do whatever you wish
       }
   }
   
   public class Purpose2 extends Target {
       public Purpose2(String address, String name, int age) {
           // set fields or do whatever you wish
       }
   }
   
   public class Purpose3 extends Target {
       public Purpose3(...) {
           // set fields or do whatever you wish
       }
   }
   

And then you may use instances of subclasses where class Target is required.