How do I tell MapStruct to use a different source if one source is null?

I have two objects of different types that are mapped to an object of a third type:

@Mapping(target = "color" //how to map this )
public abstract CombinedCar from(BlueBookCar blueBookCar , AutoTraderCar autoTraderCar);

• CombinedCar has a String field named, color.

• BlueBookCar has a String field named, color.

• AutoTraderCar has a String field named, carColor.

If BlueBookCar has a non-null color, I want to use it to set the color on CombinedCar.

Otherwise, I want to use the carColor of AutoTraderCar to set the color on CombinedCar.

How can configure MapStruct to do this?

Define an @AfterMapping method that would do the logic and set the color value:

@Mapper
public abstract class MyMapper {
  @Mapping(target = "color", ignore = true)
  public abstract CombinedCar from(BlueBookCar blueBookCar, AutoTraderCar autoTraderCar);

  @AfterMapping
  public void mapColor(
      @MappingTarget CombinedCar target, BlueBookCar blueBookCar, AutoTraderCar autoTraderCar) {
    target.setColor(
        blueBookCar.getColor() == null ? autoTraderCar.getColor() : blueBookCar.getColor());
  }
}

@Mapping(target = "color", ignore = true) is necessary to prevent error below from appearing during the build.

> java: Several possible source properties for target property "color".