Set parent target to null if source is null in MapStruct

Question

I have the following Mappings

@Mappings({
        @Mapping(source = "id", target = "id"),
        @Mapping(source = "childId", target = "child.id")
})
Entity objectDtoToEntity(ObjectDTO objectDTO);

How could I configure my Mapper or Mappings so when I have childId as null the target Entity.child would be set null not Entity.child.id?

Answer 1

Found not a very elegant solution as for me but working solution.

First change interface to abstract class then add @AfterMapping

@Mappings({
        @Mapping(source = "id", target = "id"),
        @Mapping(source = "childId", target = "child.id")
})
public abstract Entity objectDtoToEntity(ObjectDTO objectDTO);


@AfterMapping
public Entity doAfterMapping(@MappingTarget Entity entity) {
    if (entity != null && entity.getChild().getId() == null) {
        entity.setChild(null);
    }
    return entity;
}