spring-data-jpa implement custom repository with querydsl

SegmentCategoryCustomRepo.java

import java.util.Collection;
import java.util.Set;

public interface SegmentCategoryCustomRepo {
    Set<Long> findSegmentsByCategoryId(Collection<Long> categoryIds);
}

SegmentCategoryCustomRepoImpl.java

import com.google.common.collect.Sets;
import com.querydsl.jpa.impl.JPAQueryFactory;
import org.springframework.stereotype.Repository;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import java.util.Collection;
import java.util.List;
import java.util.Set;


@Repository
public class SegmentCategoryCustomRepoImpl implements SegmentCategoryCustomRepo {
    // set Repository annotate only repository implemntation
    @PersistenceContext
    EntityManager entityManager;

    @Override
    public Set<Long> findSegmentsByCategoryId(Collection<Long> categoryIds) {
        List<Long> categoryIdToSegmentIds = new JPAQueryFactory(entityManager)
                .select(segmentCategory.segment.id)
                .from(segmentCategory)
                .where(segmentCategory.category.id.in(categoryIds))
                .fetch();

        return Sets.newHashSet(categoryIdToSegmentIds);
    }
}

SegmentCategoryRepo.java

import org.springframework.data.querydsl.QueryDslPredicateExecutor;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import tv.anypoint.device.domain.SegmentCategory;

@Repository
public interface SegmentCategoryRepo extends CrudRepository<SegmentCategory, Long>, QueryDslPredicateExecutor<SegmentCategory>, SegmentCategoryCustomRepo {
    SegmentCategory findByCategoryId(long id);
}