HiberNate Oneto许多和ManyToOne抛出异常

Question

我试图建立简单的一对多关系，但hibernate抛出了错误，不知道该怎么办。

类产品：

public class Products {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @ManyToOne()
    @JoinColumn(name = "user_id", foreignKey = @ForeignKey(name = "fk_user"))
    private Users users;

}

和类用户：

public class Users {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long Id;


    @OneToMany()
    @JoinColumn(name = "product_id", foreignKey = @ForeignKey(name = "fk_product_id"))
    private List<Products> productsList = new ArrayList<>();

}

我遇到了错误：通过JDBC语句执行DDL“alter table products drop constraint fk_user”时出错

Answer 1

由于外键位于子端（Productsclass），因此可以将其放在父端，并将其引用为拥有方：

public class Users {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long Id;


    @OneToMany(mappedBy="users")
    private List<Products> productsList = new ArrayList<>();

}

Answer 2

下面是这种关系的一个实例：

抽屉类别：

@OneToMany (mappedBy="drawer", fetch = FetchType.LAZY, cascade = CascadeType.REMOVE, orphanRemoval = true)
private Set<Pocket> pockets;

袖珍类：

@ManyToOne (fetch=FetchType.EAGER)
@JoinColumn(name = "id_drawer", nullable = false)
private Drawer drawer;