如何从ManyToMany关系中获取连接表中的对象？ Spring + Hibernate

Question

我有两个实体：

@Entity
public class Customer {
@Id
@GeneratedValue
private int id;
@Column(nullable = false)
private String name;
@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private Collection<Coupon> coupons;
}

@Entity
public class Coupon {
@Id
@GeneratedValue
private int id;
@Column(nullable = false)
private String title;
@ManyToMany(mappedBy = "coupons")
private Collection<Customer> customers;
}

数据库中有三个表：customer，coupon和customer_coupons，客户可以购买优惠券，购买表后customer_coupons保存customers_id和coupons_id（客户可以有很多优惠券和优惠券可以有很多客户）。

我需要以某种方式通过customerId和couponId从customer_coupons表获得客户的优惠券。我有接口CouponRepository：

@Repository
public interface CouponRepository extends JpaRepository<Coupon, Integer> {
    @Query("SELECT c FROM Coupon c WHERE c.id IN (SELECT coupons.id FROM customer_coupons WHERE coupons_id = ?1 AND customer_id = ?2)")
    Coupon findCustomerCoupon(int couponId, int customerId);
}

但这一个查询不起作用，我得到QuerySyntaxException: customer_coupons is not mapped。有人可以帮我创建正确的查询吗？

Answer 1

来自客户的SELECT优惠券c JOIN c.coupons优惠券WHERE c.id =：customerId AND coupon.id =：couponId

来自JB Nizet的回答