Is it possible to use this library together with another JPA Data extension?

[sanemain]

I am already using another spring data JPA extension in my project, the library is hosted at this address if anyone is interested: https://github.com/darrachequesne/spring-data-jpa-datatables.

Is it possible to use jpa-entity-graph in conjunction with the other library?

[reda-alaoui]

Hi @sanemain ,

This library repository factory bean currently looks like this:

public class EntityGraphJpaRepositoryFactoryBean<
        R extends Repository<T, I>, T, I extends Serializable>
    extends JpaRepositoryFactoryBean<R, T, I> {

  /**
   * Creates a new {@link JpaRepositoryFactoryBean} for the given repository interface.
   *
   * @param repositoryInterface must not be {@literal null}.
   */
  public EntityGraphJpaRepositoryFactoryBean(Class<? extends R> repositoryInterface) {
    super(repositoryInterface);
  }

  @Override
  public void setEntityManager(EntityManager entityManager) {
    /* Make sure to use the EntityManager able to inject captured EntityGraphs */
    super.setEntityManager(RepositoryEntityManagerEntityGraphInjector.proxy(entityManager));
  }

  @Override
  protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) {
    return new EntityGraphJpaRepositoryFactory(entityManager);
  }
}

IMO, the easiest and most naive solution would be to copy its content to your own RepositoryFactoryBean like this:

public class MyCustomRepositoryFactoryBean<
        R extends Repository<T, I>, T, I extends Serializable>
    extends DataTablesRepositoryFactoryBean<R, T, I> {

  public EntityGraphJpaRepositoryFactoryBean(Class<? extends R> repositoryInterface) {
    super(repositoryInterface);
  }

  @Override
  public void setEntityManager(EntityManager entityManager) {
    super.setEntityManager(RepositoryEntityManagerEntityGraphInjector.proxy(entityManager));
  }

  @Override
  protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) {
    return new EntityGraphJpaRepositoryFactory(entityManager);
  }
}

Notice that the only difference is that this custom implementation extends DataTablesRepositoryFactoryBean instead of JpaRepositoryFactoryBean.
Then you would enable it like this:

@Configuration
@EnableJpaRepositories(repositoryFactoryBeanClass = MyCustomRepositoryFactoryBean.class)
public class MyConfiguration {}

I think a more elegant solution would require to discuss this with the Spring Data team.

[sanemain]

Thanks for the quick response @reda-alaoui . I am not sure if I understood your solution, DataTablesRepositoryFactoryBean has its own implementation of method protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager). If I extend DataTablesRepositoryFactoryBean class and override this method as suggested in your reply, this would, I believe, disable the datatables functionality all together. Am I missing something here?
The solution that comes to my mind is to write a custom repository implementation class that extends DataTables and EntityGraph repository interfaces, and delegate to corresponding implementations in methods. Something like the following, for instance:

public class CustomRepositoryImpl<T, ID extends Serializable> extends SimpleJpaRepository<T, ID> implements
		EntityGraphJpaRepository<T, ID>, EntityGraphJpaSpecificationExecutor<T>, DataTablesRepository<T, ID> {
	
        private EntityGraphJpaRepository<T, ID> entityGraphRepository;
        private DataTablesRepository<T, ID> dataTablesRepository;

	public CustomRepositoryImpl(JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager) {
		super(entityInformation, entityManager);
	}

	@Override
	public Page<T> findAll(Pageable pageable, EntityGraph entityGraph) {
		return entityGraphRepository.findAll(pageable, entityGraph);
	}
        //.....
      
        @Override
	public DataTablesOutput<T> findAll(DataTablesInput input) {
		return dataTablesRepository.findAll(input);
	}
        //.....
}

This is not enough for sure, I also need to create a new JpaRepositoryFactoryBean, copy some code from EntityGraphJpaRepositoryFactoryBean, etc. I agree that it is best to discuss with Spring Data team for a more elegant solution.

[sanemain]

@reda-alaoui I got stuck while proceeding with the solution mentioned in my reply. The reason is that RepositoryEntityManagerEntityGraphInjector and RepositoryMethodEntityGraphExtractor classes are package private, I need access to them to integrate both JPA extensions.

[reda-alaoui]

The solution that comes to my mind is to write a custom repository implementation class that extends DataTables and EntityGraph repository interfaces, and delegate to corresponding implementations in methods.

Yes you are correct, I missed this part. The solution is now very britle.

I got stuck while proceeding with the solution mentioned in my reply. The reason is that RepositoryEntityManagerEntityGraphInjector and RepositoryMethodEntityGraphExtractor classes are package private, I need access to them to integrate both JPA extensions.

I'd like to avoid turning those classes into public classes :/