@Mapper(
    nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.SET_TO_NULL,
    nullValueIterablePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE
)
public interface CustomerMapper {
    void update(Customer source, @MappingTarget CustomerDTO target);
}

When source.getItems() is null, the target's items field is left unchanged.
When source.getAddress() is null, the target's address is set to null.

Closes #3387