Convert a class to another with similar parameters (Every param has a mapping)

I have a class A like:

A {
  ClassB b;
  String a;
}

Now there is another class X like:

X {
  ClassY y;
  String a;
}

Now, ClassY is same as ClassB, like:

ClassB/ClassY {
  String b;
}

I want to copy an instance of A into a new object of Y.

I came across Dozer which does similar mapping but that was if the values are primitive. I couldn't understand how to map the classes in them. Trying to do this in java.

I came across the answer https://stackoverflow.com/a/36196948/2733350 but I could not find MapperFactory in Dozer.

Solution

You can user MapStruct. It deals pretty okay with complex objects.

To follow your example, I have created a mapper that you can adjust accordingly (@Data comes from lombok):

@Data
public class A {

    private B b;
    private String a;
}

@Data
public class B {
    private String b;
}

@Data
public class Y {

    private String b;
}

And now you can define your actual mapper:

@Mapper
public interface AMapper {

    AMapper INSTANCE = Mappers.getMapper(AMapper.class);

    @Mapping(source = "b.b", target = "b")
    Y aToY(A a);
}

A small unit test:

@Test
public void shouldMapAToY() {
    A a = new A();
    a.setA("a variable");
    final B b = new B();
    b.setB("stuff from class b");
    a.setB(b);

    Y y = AMapper.INSTANCE.aToY(a);
    assertThat(y).isNotNull();
    assertThat(y.getB()).isEqualTo(b.getB());
}