删除具有 manyToMany 关系的 spring 对象时，如何避免“无法删除或更新父行”错误？

Question

when deleting a spring object, that has manyToMany relationship with another spring object - how do i avoid the "cant delete or update a parent row, a foreign key constraint fails " error?

this is the method that is failing.

(coupon is the spring object we are attempting to delete)

public void deleteCoupon(Coupon coupon) throws CouponsSystemExceptions {
        if (!companyHasCouponPurchased(coupon)) {
            throw new CouponsSystemExceptions(SystemExceptions.ILLEGAL_ACTION_ATTEMPTED,
                    "The company does not have this coupon");
        }
        couponRepository.delete(coupon);
        System.out.println("\n--The coupon was deleted--\n");
    }

this is the mapping of the relationship with the other object "Customer"

@ToString.Exclude
    @ManyToMany(mappedBy = "coupons")
    private List<Customer> customers;
this is the mapping of the "customer" object relationship with the coupon object
@ToString.Exclude
    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(name = "customers_vs_coupons", joinColumns = @JoinColumn(name = "CUSTOMER_ID"), inverseJoinColumns = @JoinColumn(name = "COUPON_ID"))
    private List<Coupon> coupons;

and this is the error that spring gives:

Exception in thread "main" org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement;

WHICH IS CAUSE BY :
Caused by: java.sql.SQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails (`coupon_system2`.`customers_vs_coupons`, CONSTRAINT `FKqic70ugf37j3rc4og2t3xp0ah` FOREIGN KEY (`COUPON_ID`) REFERENCES `coupons` (`id`))

Answer 1

You need to define a one to many relation in Customer and Coupon object. The relationship currently does not look correct. One customer may have many coupons so a customer object will contain a one to many relationship with the coupons object and use cascade = CascadeType.REMOVE options for foreign key issues. In database you should also add this option if not existing already.