我有4个实体，彼此之间有@OneToMany关系。当我尝试保存包含OrderItem的Order时，Orderitem没有反向引用。
在下面的代码中，为了简洁起见，只显示了重要的字段（通常的字符串和原语被省略了）。我决定还包括Dish和User实体。

订单：

@Entity
@NoArgsConstructor
@Getter
@Setter
@ToString
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    @ManyToOne(fetch = FetchType.LAZY)
    private User user;

    @OnDelete(action = OnDeleteAction.CASCADE)
    @OneToMany(
        mappedBy = "order",
        cascade = CascadeType.ALL,
        fetch = FetchType.EAGER,
        orphanRemoval = true)
    private List < OrderItem > orderItems;
}

菜品：

@Entity
@NoArgsConstructor
@Getter
@Setter
@ToString
public class Dish {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @OneToMany(cascade = CascadeType.ALL,
        fetch = FetchType.LAZY,
        mappedBy = "dish")
    @ToString.Exclude
    private List < OrderItem > orderItems;
}

订单项目：

@Entity
@NoArgsConstructor
@Getter
@Setter
@ToString
public class OrderItem {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    @ManyToOne(fetch = FetchType.LAZY)
    @ToString.Exclude
    private Dish dish;
    @ManyToOne(fetch = FetchType.LAZY)
    private Order order;
    private int quantity;
}

使用者：

@Entity
@NoArgsConstructor
@Getter
@Setter
@ToString
@Table(name = "users")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)

    @OneToMany(
        mappedBy = "user",
        cascade = CascadeType.ALL,
        orphanRemoval = true
    )
    private List < Order > orders;
}

当我试图用Spring Data JPA保存Order时，出现了这个问题。让我们在保存之前打印Order以查看OrderItem。

public Order saveOrder(Order order) {
    System.out.println("SERVICE saving order " + order);
    return orderRepository.save(order);
}

正如您所看到的，orderItems backreference在保存之前为null（我认为spring data jpa应该处理它的设置）。
服务保存订单订单（标识=0，orderItems=[订单项（标识=0，数量=2，订单=空）]）
下面是我在DB中的内容（Order和OrderItem实体）。