JHipster EntityMapper interface (mapstruct): map a Spring projection interface - jhipster

Question

I've generated a new project with JHipster v4.6.0 generator and I'm using its EntityMapper interface to do the mapping between domain and DTO objects.
public interface EntityMapper <D, E> {
public E toEntity(D dto);
public D toDto(E entity);
public List <E> toEntity(List<D> dtoList);
public List <D> toDto(List<E> entityList);
}
I need to use the Spring projection to have a smaller domain and DTO objects, (I don't want all fields of the entity), so I've created an interface with only the getters of the fields I need, and I've created a method in the repository which retrive this interface type (following the Spring reference guide)
public interface ClienteIdENome {
Long getId();
String getNome();
}
#Repository
public interface ClienteRepository extends JpaRepository<Cliente,Long> {
ClienteIdENome findById(Long id);
}
The query findById retrieve a ClienteIdENome object with only id and nome fields.
Now, I would like to map this object in the following DTO:
public class ClienteIdENomeDTO implements Serializable {
private static final long serialVersionUID = 1L;
private Long id;
#NotNull
#Size(max = 50)
private String nome;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getNome() {
return nome;
}
public void setNome(String nome) {
this.nome = nome;
}
}
So, I created the mapper interface:
#Mapper(componentModel = "spring", uses = {})
public interface ClienteIdENomeMapper extends EntityMapper<ClienteIdENomeDTO, ClienteIdENome> {
}
But Eclipse report to me an error in the EntityMapper interface for the method "public E toEntity(D dto)" with the message:
No implementation type is registered for return type it.andrea.ztest01.repository.ClienteIdENome.
Any help?
Thanks a lot

Answer 1

Your ClienteIdENome is not really an entity. I would argue that you don't need to use the EntityMapper, but you need to define a one way mapper. From ClienteIdENome to ClienteIdENomeDTO.
Your mapper needs to look like:
public interface ClienteIdENomeMapper {
ClienteIdENomeDTO toDto(ClienteIdENome entity);
List <ClienteIdENomeDTO> toDto(List<ClienteIdENome> entityList);
}
I don't know JHipster, so I can't say what will mean using a mapper different than EntityMapper.