Mapstruct not selecting overloaded method for optional properties generated by Immutables

Question

I'm using Immutables to generate some classes DTO classes, and Mapstruct to map JPA entities to DTOs. This works great, as long as the DTO has only required properties. If a property is not required (by making the accessor method return an Optional , as per thedocs ), the builder generated by Immutables will have a setter method with an Optional argument, which Mapstruct will fail on:

 error: Can't map property "java.lang.Integer id" to "java.util.Optional<java.lang.Integer> id". Consider to declare/implement a mapping method: "java.util.Optional<java.lang.Integer> map(java.lang.Integer value)".

Makes sense, thankfully there's an option available to also generate methods that take nullable arguments instead. This option generates an additional method that takes a nullable argument. However, Mapstruct seems to fail regardless of the presence of this method.

As a workaround, I implemented this abomination (but at this point I'd rather implement the mapping methods myself):

@Mapper
public class OptionalMapper {

    public <T> T unwrapOptional(final Optional<T> optional) {
        return optional.orElse(null);
    }

    public <T> Optional<T> wrapIntoOptional(final T value) {
        return Optional.ofNullable(value);
    }

Is there any way to make Mapstruct look for overloaded methods (or see the "correct" one first)? Am I going about this the wrong way or simply missing something? Thanks!

Answer 1

Currently writing that custom OptionalMapper is the way to perform the unwrapping of the optionals.

I don't think that doing that is a bad thing. There is an open issue for supporting Optional