How to apply function of two arguments mapping objects using MapStruct?

Question

There are two source classes A and B

class A {
    public Double x;
    public Double y;
}

class B {
    public Double x;
    public Double y;
}

and another target class C

class C {
    public Double x;
    public Double y;
}

It is clear how to map A to C or B to C.

Is it possible to map some function, for example, addition or pow of source objects to the target one so that the generated code will look like this

C.x = A.x + B.x
C.y = A.y + B.y

or

C.x = Math.pow(A.x, B.x)
C.y = Math.pow(A.y, B.y)

Answer 1

This can be done by using expressions.

@Mapper
public interface MyMapper {

    @Mapping(target = "x", expression = "java(a.x + b.x)")
    @Mapping(target = "y", expression = "java(a.y + b.y)")
    C map(A a, B b);
}

or

@Mapper
public interface MyMapper {

    @Mapping(target = "x", expression = "java(Math.pow(a.x, b.x))")
    @Mapping(target = "y", expression = "java(Math.pow(a.y, b.y))")
    C map(A a, B b);
}

More info about expressions can be found in the reference documentation here