@Mapper(uses = {
  BOIdMapper.class,
  DateMapper.class,
  CarVOFactory.class,
})
public interface CarMapper {
   CarMapper INSTANCE = Mappers.getMapper(CarMapper .class);

   @Mappings({
     @Mapping(source = "VOKey", target = "id"),
     @Mapping(source = "gueltAb", target = "gueltigAb")
   })
   Car map(CarVO carVO);

   @InheritInverseConfiguration
   CarVO map(Car car);

   public class CarVOFactory {
      public CarVO createCarVO() {
         return VOFactory.createVO(CarVO.class);
      }
   }
}

public class Car {

    private String id;
    private LocalDate gueltigAb;
    ...
}

public interface CarVO extends ... {
    void setVOKey (VOKey<CAR> voKey);
}

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2017-08-29T08:55:10+0200",
    comments = "version: 1.1.0.Final, compiler: Eclipse JDT (IDE) 1.2.100.v20160418-1457, environment: Java 1.8.0_102 (Oracle Corporation)"
)

public class CarMapperImpl implements CarMapper {
    private final BOIdMapper bOIdMapper = new BOIdMapper();
    private final DateMapper dateMapper = new DateMapper();
    private final CarVOFactory CarVOFactory = new CarVOFactory();

    @Override
    public Car map(CarVO CarVO) {
        if ( CarVO == null ) {
            return null;
        }
        Car Car = new Car();
        Car.setGueltigAb( dateMapper.asLocalDate( CarVO.getGueltAb() ) );
        Car.setId( bOIdMapper.asId( CarVO.getVOKey() ) );
        return Car;
   }
    @Override
    public CarVO map(Car Car) {
        if ( Car == null ) {
            return null;
        }
        CarVO CarVO = CarVOFactory.createCarVO();
        return CarVO;
   }