Polymorphism with respect to performance

Question

I got the following problem. I want to create SomeObject. This object consists of various nested objects NestedObject1, NestedObject2, ... I created mappers to create those nested objects Mapper1 to create NestedObject1, Mapper2 to create NestedObject2, and so on. Those Mappers call a huge amount of setters, and some of them need information from some entites from the db (and some don't). This is the problem in the java language:

public class MyClass {

    @Inject
    private MyDao dao;

    @Inject
    private Mapper1 mapper1;
    @Inject
    private Mapper2 mapper2;
    @Inject
    private Mapper3 mapper3;
    @Inject
    private Mapper4 mapper4;
    @Inject
    private Mapper5 mapper5;

    public SomeObject map(Integer id) {
        SomeEntity entity = dao.findById(id);

        SomeObject someObject = new SomeObject();
        someObject.setNestedObject1(mapper1.map(entity));
        someObject.setNestedObject2(mapper2.map());
        someObject.setNestedObject3(mapper3.map(entity));
        someObject.setNestedObject4(mapper4.map(entity));
        someObject.setNestedObject5(mapper5.map());
        return someObject;
    }

}

I am thinking of the following refactoring: Make an interface Mapper and have all mappers implement this. Then I could inject the List of mappers. It would be pretty easy to add or remove on mapper, without touching MyClass. I think this is a good idea but the problem is the MyDao. Instead of one DB access I would then need 3.

The interface would then look like

public interface Mapper {

    public void map(SomeObject someObject);

}

Mapper1 would look like

public class Mapper1 implements Mapper {

    private static final Integer VALUTA = 1;

    @Inject
    private MyDao dao;

    @Override
    public void map(SomeObject someObject) {
         SomeEntity entity = dao.findById(id);  // and I have no idea what the id is

         NestedObject1 nestedObject1 = new NestedObject1();
         nestedObject1.setSomeField(entity.getSomething());
         nestedObject1.setSomeOtherField(VALUTA);

         someObject.setNestedObject1(nestedObject1);
    }

}

id is unknown in this context. Include id in the signature? I have no idea... Mapper3 and Mapper4 would have to look up the entity as well.

I was thinking about an abstract class which will look for the entity in the BeforeClass method, but I think this still get's called multiple times.

Btw: I know the title sucks, please feel free to rename it.