Depending on a generic SuperBuilder

[Marc Guilera]

I have a base entity which has a couple of properties and the concrete implementation with a couple of extra ones. On top of that I need the base class to access "self" of the child which I do through generics. Here is a simplified example of what I am trying:

@Data

@SuperBuilder(toBuilder = true)

@ToString(callSuper = true)

public abstract class Entity<ENTITY extends Entity<ENTITY, BUILDER>, BUILDER extends Entity.EntityBuilder<ENTITY, BUILDER, ENTITY, BUILDER>> implements Mutable<ENTITY> {

    //...

    public abstract ENTITY mutate(Consumer<Context<ENTITY, BUILDER>> context) {

        var builder = createBuilder();

        context.accept(new Context<>(self(), builder));

        return builder.build();

    }

    protected abstract ENTITY self();

    protected abstract BUILDER createBuilder();

}

@Data

@SuperBuilder(toBuilder = true)

public class SubEntity extends Entity<SubEntity, Entity.EntityBuilder<?, ?>> {

    //...

    @Override

    protected SubEntity self() {

        return this;

    }

    @Override

    protected SubEntity.SubEntityBuilder<?, ?> createBuilder() {

        return toBuilder();

    }

}

The issue is in the Entity.EntityBuilder<?, ?> part where it complains that EntityBuilder is not accessible in current context. How can I achieve my goal? 

Thanks in advance.

[Floris Kraak]

Superbuilder and generics is a rabbit hole. That annotation is using some very fancy tricks to work but combining it with generics is liable to blow up.

I would suggest making the base entity an '@Embeddable' annotated object instead, and embedding it I the concrete class with '@Embedded'. That way you can have the same set of columns but without the pain that is inheritance and generics 

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[Floris Kraak]

Another suggestion: Try running your code through delombok, that way you will see exactly what is being generated here.

[Marc Guilera]

I called it an "Entity" but it's just a model, I am not using JPA in the project so @Embedable is not feasible. Delegate is also not possible since it only goes one level up. 

[Floris Kraak]

The person to ask about this stuff is Jan Rieke, it's his feature.

This example is definitely stretching superbuilder to the limits though, combining generics with customized builders and inheritance.

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