[FIXED] Mapstruct - nullValueMappingStrategy do not return null when set to ReturnNull

Issue

I migrate a project that use mapstruct from version 1.4.x to version 1.5.2.Final

In the existing code, there is a test that assert that if i try to map a null source to an existing target, the return should be null. This test no longer works.

After reading docs and post on stackoverflow, i set my mapping like this :

@Mapper(
        componentModel = "spring",
        nullValueMappingStrategy = RETURN_NULL,
        nullValuePropertyMappingStrategy = SET_TO_NULL,
        nullValueCheckStrategy = ALWAYS,
        uses = {TariffDataMapper.class}
)
public interface ActDataMapper {

    @Mappings({
            @Mapping(target = "id", ignore = true),
            @Mapping(target = "Tarifs", source = "source.capitalAtRisk.Tarifs"),
            @Mapping(target = "invalidityTariffs", source = "source.capitalAtRisk.invalidityTariffs")
    })
    @BeanMapping( nullValueMappingStrategy = RETURN_NULL)
    ActEntity updateEntity(Act source, @MappingTarget @NonNull ActEntity target);

I even try to override updateEntity method mapping with @BeanMapping, but the generated code is still the same :

    @Override
    public ActEntity updateEntity(Act source, ActEntity target) {
        if ( source == null ) {
            return target;
        }
     ...
    }

Where i expect the method to return null instead of target if source is null.

Could you please tell me where i'm wrong ?

Have a nice day.

Solution

When using update mappings with a return type then returned value will always be what was passed in @MappingTarget. The nullValueMappingStrategy does not have an impact on update mapping return values.

This is explained in the Updating existing bean instances section of the MapStruct documentation

Answered By - Filip
Answer Checked By - Robin (JavaFixing Admin)