java - Hibernate - JPA - oneToMany - 算作子查询并用作谓词

Question

我有以下关系，我需要获得至少有一次购买的消费者（作为子查询，因为这是更大查询的一部分）。

@Entity
@Table(name = "consumers")
public class Consumer extends User {

@JsonIgnore
    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "consumer_id")
    private List<Purchase> purchases;
}

和查询

CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Consumer> criteriaQuery = criteriaBuilder.createQuery(Consumer.class);
Root<Consumer> root = criteriaQuery.from(Consumer.class);`
Join<Consumer, Purchase> purchases = root.join(Consumer_.purchases, JoinType.LEFT);
                    sub.select(criteriaBuilder.count(purchases.get(Purchase_.id)));
                    sub.where(criteriaBuilder.equal(root.get(Consumer_.id), purchases.get(Purchase_.consumer).get(Consumer_.id)));
                    predicates.add(criteriaBuilder.greaterThanOrEqualTo(sub, 0L));