Spring DATA JPA @ManyToOne：外键为空答案

【问题标题】：Spring DATA JPA @ManyToOne : foreign key is nullSpring DATA JPA @ManyToOne：外键为空
【发布时间】：2022-11-15 15:15:58
【问题描述】：

当我要完美保存订单但订单表外键始终为空时！

我正在使用 Mysql 数据库。

这是我的实体关系：


@Entity
@AllArgsConstructor
@NoArgsConstructor
@Data
@Table(name = "orders")
public class Order implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int orderID;
    private double total;


    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "userID", referencedColumnName = "username")
    private User userID;

    @OneToMany(mappedBy = "order", fetch = FetchType.LAZY)
    private List<OrderDetails> orderDetails;
}

@Entity
@AllArgsConstructor
@NoArgsConstructor
@Data
@Table(name = "orderdetails")
public class OrderDetails {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int orderDetailsId;
    private int qty;

    @OneToOne
    @JoinColumn(name = "productId", referencedColumnName = "productId")
    private Product productId;

    @ManyToOne
    @JsonIgnore
    @JoinColumn(name = "orderId", referencedColumnName = "orderID")
    private Order order;

}

所有主键都是自动生成的。

【问题讨论】：

标签： java spring-boot spring-data-jpa relational-database

【解决方案1】：

也许你只添加@JoinColumn(foreignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT))

【讨论】：