Improve Querydsl support in custom repositories [DATACMNS-898]

[spring-projects-issues]

Andrei Ivanov opened DATACMNS-898 and commented

Hi, As far as I understand from the documentation, working with Querydsl in a repository means that the repository interface should extend QueryDslPredicateExecutor:

public interface SiteAccessRequestsRepository extends PagingAndSortingRepository<SiteAccessRequest, Long>, QueryDslPredicateExecutor<SiteAccessRequest> {
}

This seems a bit weird to me because now the "query" gets created in the service/facade layer:

import com.example.siteaccess.dao.expressions.SiteAccessRequestExpressions;
@Service
public class SiteAccessRequestsFacadeImpl implements SiteAccessRequestsFacade {

    @Override
    public Page<SiteAccessRequest> getSiteAccessRequests(SiteAccessRequest probe, Pageable pageable) throws BusinessException {
        Predicate predicate = SiteAccessRequestExpressions.byExample(probe);
        return siteAccessRequestsRepository.findAll(predicate, pageable);
    }
}

And this also make integration testing difficult, as this is similar to having a method like findAll(String sql) defined in the repository interface.

So I tried to create a custom repository for this:

interface SiteAccessRequestsRepositoryCustom {
    Page<SiteAccessRequest> findByExample(SiteAccessRequest probe, Pageable pageable);
}

public class SiteAccessRequestsRepositoryImpl extends QueryDslRepositorySupport implements SiteAccessRequestsRepositoryCustom {

    public SiteAccessRequestsRepositoryImpl() {
        super(SiteAccessRequest.class);
    }

    @Override
    public Page<SiteAccessRequest> findByExample(SiteAccessRequest criteria, Pageable pageable) {
        Predicate predicate = SiteAccessRequestExpressions.byExample(criteria);
        //JPQLQuery<?> countQuery = createQuery(predicate);

        return null;
    }
}

This is were I got stuck. When using the QueryDslPredicateExecutor, the findAll(Predicate predicate, Pageable pageable) method is handled by QueryDslJpaRepository. But QueryDslRepositorySupport has only some basic methods to perform queries. What I am suggesting is to move some of the methods from QueryDslJpaRepository to QueryDslPredicateExecutor to make this case easier to implement.

Or maybe there already is a better way to implement custom repositories with Querydsl that I haven't seen?

---

Affects: 1.12.2 (Hopper SR2)

[spring-projects-issues]

Oliver Drotbohm commented

What exactly are you missing in QueryDslRepositorySupport? It basically allows you to call from(SiteAccessRequest.class).where( SiteAccessRequestExpressions.byExample(criteria))… and by that move that logic into the repository layer if desired

[spring-projects-issues]

Andrei Ivanov commented

Well, at least QueryDslJpaRepository.findAll(Predicate predicate, Pageable pageable) content I would have to copy/paste in my own method. Then from(SiteAccessRequest.class) doesn't seem to work, as QueryDslRepositorySupport.from expects an EntityPath (I see these are created in the constructor of QueryDslJpaRepository)

[spring-projects-issues]

Oliver Drotbohm commented

My mistake, I am not near any IDE right now. I guess it expects a Querydsl root path then. Something from the meta-model it generates, like QUser.user or the like.

So it boils down to the lack of application of Pageable?

[spring-projects-issues]

Andrei Ivanov commented

At least for what I'm doing now, I think so. Even for a simple query I think it would be nice to get an example in the documentation about this combination of custom repository and Querydsl

[spring-projects-issues]

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