SpringBoot: create object from generic type in generic mapper

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I have a lot of entity extend Catalog entity and as well as have a lot of dto that extent CatalogDto

Catalog Entity

And I have a generic repository, service, and mapper as follows

My repository:

@Repository
public interface CatalogRepository<T extends Catalog> extends JpaRepository<T, Integer>{
}

My service:

@Service
@Transactional
public class CatalogServiceImpl<T extends Catalog,Dto extends CatalogDto>{
    private final Logger log = LoggerFactory.getLogger(CatalogServiceImpl.class);

    private final CatalogRepository<T> repository;
    private CatalogMapper<T,Dto> catalogMapper=new CatalogMapper<T,Dto>() {};

    public CatalogServiceImpl(CatalogRepository<T> repository) {
        this.repository = repository;
    }
}

My Mapper:

public abstract class CatalogMapper<T extends Catalog,Dto extends CatalogDto> implements Rapper<T,Dto> {
    @Override
    public Dto entityToDto(T entity) {
        return null;
    }

    @Override
    public T dtoToEntity(Dto dto) {
        return null;
    }
}

I want to create an object from T in dtoToEntity method and an object from Dto in entityToDto method in CatalogMapper class

spring-boot spring generics java
1 Answers

I think that these two methods should be abstract because every mapper probably works in different ways. Anyway you can provide a base implementation like this

public T dtoToEntity(Dto dto) throws InstantiationException, IllegalAccessException {
    T entity = (T) ((Class)((ParameterizedType)this.getClass().
               getGenericSuperclass()).getActualTypeArguments()[0]).newInstance();
    BeanUtils.copyProperties(dto, entity);
    return entity;
}

public Dto entityToDto(T entity) throws InstantiationException, IllegalAccessException {
    Dto dto = (Dto) ((Class)((ParameterizedType)this.getClass().
               getGenericSuperclass()).getActualTypeArguments()[1]).newInstance();
    BeanUtils.copyProperties(entity, dto);
    return dto;
}

Using ParameterizedType of the generic class you can create a new instance and then execute a simple copyProperties

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