@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"),
        inverseJoinColumns = @JoinColumn(name = "item_id"))
    private List<Item> items = new ArrayList<>();

    @ManyToOne
    @JoinColumn(name = "parent_id")
    private Category parent;

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

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

}

Delivery.java

@Entity
@Getter
@Setter
public class Delivery {

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

    @OneToOne(mappedBy = "delivery", fetch = FetchType.LAZY)
    private Order order;

    @Embedded
    private Address address;

    @Enumerated(EnumType.STRING)
    private DeliveryStatus status; // Ready, Comp
}

DeliveryStatus.java

public enum DeliveryStatus {
    READY, COMP
}

@Entity
@Getter @Setter
public class Member {

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

    private  String name;

    @Embedded
    private Address address;

    @OneToMany(mappedBy = "member")
    private List<Order> orders = new ArrayList<>();
}

Order.java

@Entity
@Table(name = "orders")
@Getter
@Setter
@NoArgsConstructor(access = AccessLevel.PROTECTED)
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", cascade = CascadeType.ALL)
    private List<OrderItem> orderItems = new ArrayList<>();

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

    private LocalDateTime orderDate; // 주문시간

    @Enumerated(EnumType.STRING)
    private OrderStatus status; // 주문상태 [ORDER , CANCEL]

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

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

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

    // 생성 메서드
    public static Order createOrder(Member membger, Delivery delivery, OrderItem... orderItems) {
        Order order = new Order();
        order.setMember(membger);
        order.setDelivery(delivery);

        for (OrderItem orderItem : orderItems) {
            order.addOrderItem(orderItem);
        }
        order.setStatus(OrderStatus.ORDER);
        order.setOrderDate(LocalDateTime.now());
        return order;
    }

    // 비즈니스 로직

    /**
     * 주문 취소
     */
    public void cancel() {
        if (delivery.getStatus() == DeliveryStatus.COMP) {
            throw new IllegalStateException("이미 배송완료된 상품은 취소가 불가능합니다");
        }

        this.setStatus(OrderStatus.CANCEL);
        for (OrderItem orderItem : orderItems) {
            orderItem.cancel();
        }
    }

    // 조회 로직

    /**
     * 전체 주문 가격 조회
     */
    public int getTotalPrice() {
        return orderItems.stream().
            mapToInt(OrderItem::getTotalPrice).
            sum();
    }
}