☑️[SPRING] 양방향 연관관계일 때 연관관계 편의 메서드를 만들어보장

@Entity
@Table(name="orders")
@Getter @Setter
public class Order {

    @Id @GeneratedValue
    @Column(name = "order_id")
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "member_id")
    private Member member;

    @OneToMany(mappedBy = "order")
    private List<OrderItem> orderItems = new ArrayList<>();

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "delivery_id")
    private Delivery delivery;

    private LocalDateTime orderDate;

    @Enumerated(EnumType.STRING)
    private OrderStatus status;

    //== 연관관계 메서드 ==
    public void setMember(Member member){
        this.member = member;
        member.getOrders().add(this);
    }

    public void addOrderItem(OrderItem orderItem){
        this.orderItems.add(orderItem);
        orderItem.setOrder(this);
    }

    public void setDelivery(Delivery delivery){
        this.delivery = delivery;
        delivery.setOrder(this);
    }
}

@Entity
@Getter @Setter
public class Category {
    @Id @GeneratedValue
    @Column(name = "category_id")
    private Long id;

    private String name;

    @ManyToMany
    @JoinTable(name="category_item",
        joinColumns = @JoinColumn(name = "category_id"), // 테이블의 연관관계 주인쪽에 들어가는 부분
        inverseJoinColumns = @JoinColumn(name = "item_id") //테이블의 맵핑 되는쪽에 들어가는 부분
    )
    private List<Item> items = new ArrayList<>();

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "parent_id")
    private Category parent;

    @OneToMany(mappedBy = "parent")
    private List<Category> child = new ArrayList<>();

    public void addChildCategory(Category child){
        this.child.add(child);
        child.setParent(this);
    }
}