Use update mehtod mapping from other mapper - mapstruct

Question

I am having two Mappers
#Mapper(uses= {ChildMapper.class})
public abstract class ParentMapper {
#Mappings...
public abstract Parent dtoToParent(
final ParentDto dto);
#InheritConfiguration(name = "dtoToParent")
public abstract Parent updateParentFromDto(
final ParentDto dto,
final #MappingTarget Parent parent);
}
#Mapper()
public abstract class ChildMapper {
Child dtoToChild(
final ChildDto dto);
Set<Child> dtosToChilds(
final Set<ChildDto> childs);
Child updateChildFromDto(
final ChildDto dto,
final #MappingTarget Child geo);
}
When generating the implementation, how do I instruct MapStruct to use updateChildFromDto method inside the the method updateParentFromDto. It is generating with dtosToChilds which in-turn uses dtoToChild method.
Reason, when object is present, I want to update the properties rather than creating new, while when not present create new.

Answer 1

How would MapStruct even (in a generic way) recognise whether the object is present in the destination set?
But nothing is blocking you to write your own implementation to do that.. Something like this:
#Mapper()
public abstract class ChildMapper {
abstract Child dtoToChild(ChildDto dto);
abstract Child updateChildFromDto( ChildDto dto, #MappingTarget Child geo);
Set<Child> dtosToChilds(final Set<ChildDto> childs);
// NOTE the void, I don't like to return a mapping target. MapStruct calls
// update methods from update methods an regular methods from regular methods
// using both in one signature, things tend to get blurry
void updateDtosToChilds(Set<ChildDto> childs, #MappingTarget Set<Child> target){
for ( ChildDto child : childs {
Child targetChild = null;
// get matching child from target
if ( targetChild != null ) {
updateChildFromDto( child, targetChild );
}
else {
target.add( dtoToChild( child ) );
}
}
}
}
and like indicated above, don't do:
#InheritConfiguration(name = "dtoToParent")
public abstract Parent updateParentFromDto(
final ParentDto dto,
final #MappingTarget Parent parent);
but rather
#InheritConfiguration(name = "dtoToParent")
public abstract void updateParentFromDto(
final ParentDto dto,
final #MappingTarget Parent parent);