https://stackoverflow.com/questions/56720239/how-to-do-projection-in-spring-data-jpa

WhatsappChatDTO.java

@Value
class WhatsappChatDTO{
  String whatssappid, name;  
}

// or comment above and uncomment below

/*
interface WhatsappChatDTO{
  String getWhatsappid();
  String getName();
}
*/

WhatsappChatRepository.java

@Repository
public interface WhatsappChatRepository extends JpaRepository<WhatsappChat, Long>{
  @Query("SELECT DISTINCT W.whatsappid, W.name  FROM WhatsappChat W")
  List<WhatsappChatDTO> findAllContacts();
}


// say you have Long for entity id

//By this repository you don't need to convert your entities to DTO's. It is converted implicitly

WhatsappChatService.java

@Service
public class WhatsappChatService{
  @Autowired
  private WhatsappChatReposiotry repository;

  public List<WhatsappChatDTO> listAllContacts(){
    return repository.findAllContacts();
  }
}