Mapstruct generated class uses Lombok builder from parent instead of child

问题

I have class A (domain class), class B (mongo db repository layer class) extends A and both of them have Lombok @Builder on them. I need to convert between them and when I use Mapstruct for this, the implementation conversion class uses Builder from A when generating object of type B. This results in build failure due to "incompatible types". How to fix this?

@Builder
class A {

}

@Document
@Builder
class B extends A{
}

@Mapper
public interface ClassMapper {
   B mapToDocument(A domainObject);
}

This code generates the following Mapstruct file:

public class ClassMapperImpl implements ClassMapper{
   @Override
   public B mapToDocument(A domainObject){
      if(domainObject == null){
         return null;
      }
      Builder builder = A.builder();
      //builder methods
      return builder.build(); //incompatible types due to builder generating A objects, not B
   }
}

回答1:

your code cannot compile even without the mapper. Lombok complains that the @Builder in B class has incompatible type returned:

The return type is incompatible with A.builder()

because .builder() method is static, it cannot use inheritance mechanism.

another solution is to use @Getter on A class and @Setter on B class and let mapstruct do the mapping for you.

回答2:

@Builder does not work well in combination with inheritance. However, mapstruct also works with @SuperBuilder, which is designed for such a use case.

Remove all @Builders and put @SuperBuilder on all classes along the inheritance hierarchy.

回答3:

It's possible disable the builder, see the manual https://mapstruct.org/documentation/stable/reference/html/#mapping-with-builders

In case you want to disable using builders then you can use the NoOpBuilderProvider by creating a org.mapstruct.ap.spi.BuilderProvider file in the META-INF/services directory with org.mapstruct.ap.spi.NoOpBuilderProvider as it’s content.

this resolve the issue

来源：https://stackoverflow.com/questions/58929524/mapstruct-generated-class-uses-lombok-builder-from-parent-instead-of-child

标签

java

mongodb

Lombok

mapstruct