I'm new to Mapstruct and I'm trying to understand it properly.

What I want to achieve is converting from a DTO String parameter (carModel) to his Entity, retrieve using Service and Repository.

The problem is that Mapper class generated by Mapstruct is trying to inject the Service class with @Autowired annotation, but it's not working. The service is null.

Here's my @Mapper class:

@Mapper(componentModel = "spring", uses = CarModelService.class)
public interface KitMapper extends EntityMapper<KitDTO, Kit> {
    KitMapper INSTANCE = Mappers.getMapper(KitMapper.class);

    @Mapping(source = "weight", target = "systemWeight")
    @Mapping(source = "carModel", target = "carModel")
    Kit toEntity(KitDTO kitDTO);
}

public interface EntityMapper<D, E> {
    E toEntity(D dto);
    List<E> toEntity(List<D> dtoList);
}

The @Service class:

@Service
@Transactional
public class CarModelService {
    private final CarModelRepository carModelRepository;

    @Transactional(readOnly = true)
    public CarModel findByName(String name) {
        return carModelRepository.findByName(name).orElse(null);
    }
}

The @Repository class:

@Repository
public interface CarModelRepository extends JpaRepository<CarModel, Long> {
    Optional<CarModel> findByName(String carModelName);
}

The DTO and Entity classes:

public class KitDTO {
    private String id;
    private String carModel; // e.g. "Ferrari Monza"
    ....
}

@Entity
@Table(name = "kit")
public class Kit implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
    @SequenceGenerator(name = "sequenceGenerator")
    @Column(name = "id")
    private Long id;

    @ManyToOne
    private CarModel carModel;

    ...
}

@Entity
@Table(name = "car_model")
public class CarModel implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
    @SequenceGenerator(name = "sequenceGenerator")
    @Column(name = "id")
    private Long id;

    @Column(name = "name")
    private String name;

    ...
}

The build work properly but the application stop when I try to use the Mapper. It says that carModelService is null. Here's the mapper generated implementation class:

@Component
public class KitMapperImpl implements KitMapper {

    @Autowired // <-- this seems not working
    private CarModelService carModelService;

    @Override
    public Kit toEntity(KitDTO kitDTO) {
        if ( kitDTO == null ) {
            return null;
        }

        Kit kit = new Kit();

        kit.setSystemWeight( String.valueOf( kitDTO.getWeight() ) );
        kit.carModel( carModelService.findByName(kitDTO.getCarModel()) ); // <-- carModelService is null!

        // other setters

        return kit;
    }
}

I've tried many things, using Decorator, @Context, expression, inject the @Mapper class into the @Service class.

I've found many questions but actually no one helped me:

Mapstruct - How can I inject a spring dependency in the Generated Mapper class

@Service Class Not Autowired in org.mapstruct.@Mapper Class

MapStruct mapper not initialized with autowired when debug

Any help would be appreciated! Thanks in advance!

CodePudding user response：

Can you please share the error message? From the information that you shared, I can see the carModel in KitDto is String and in Entity is CarModel class. Not sure how mapstruct's auto generated implementation class implemented this: kit.carModel( carModelService.findByName(kitDTO.getCarModel()) );.

But I would like to share another approach,Don't know this is a best practice or not. In this approach you can create a abstarct class of mapper, in which you can @Autowired repository can manually add those mapping. I shared the snippet for it. Hopefully this will help you.

    @Mapper(componentModel = "spring", nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE)
public abstract class ProductMapper {
    @Autowired 
    private CarModelService carModelService;
    
    public abstract Kit convertDTOToEntity(KitDTO kitDTO);
    
       public Kit toEntity(KitDTO kitDTO);
        {   
        Kit kit = convertDTOToEntity(kitDTO);
        kit.setCarModel(carModelService.findByName(kitDTO.getCarModel()));
        return kit;
        }
    }

Curious about the other approaches, will follow this thread. We can discuss the best practices

CodePudding user response：

Found the solution!

Instead of calling directly the Mapper method toEntity() from the @RestController class, I injected the mapper in the CarModelService class and created a method that call the mapper. In this way the flow is:

Controller --> Service --> Mapper

@Service
@Transactional
public class KitService {
    private final KitRepository kitRepository;

    private final KitSearchRepository kitSearchRepository;

    private final KitMapper kitMapper; // <-- mapper declaration

    public KitService(KitRepository kitRepository, KitSearchRepository kitSearchRepository, KitMapper kitMapper) {
        this.kitRepository = kitRepository;
        this.kitSearchRepository = kitSearchRepository;
        this.kitMapper = kitMapper; // <-- mapper initilization
    }

    // here the method which calls mapper
    public Kit convertDTOToEntity(KitDTO kitDTO) {
        return kitMapper.toEntity(kitDTO);
    }

In this way, the generated class by Mapstruct doesn't give error on the CarModelService.

Seems like this approach is the only way to achieve this, create a king of "bridge" between services and mappers.

(You can use also the @Autowired annotation instead of constructor)