#2-4. [스프링 핵심 원리-기본편] - 주문과 할인 도메인 개발

[주문과 할인 도메인 설계]

- 회원은 상품을 주문할 수 있다.

- 회원 등급에 따라 할인 정책을 적용할 수 있다.

- 할인 정책은 모든 VIP는 1000원을 할인해주는 고정 금액 할인을 적용해달라(변경 가능)

- 회사의 기본 할인 정책을 아직 정하지 못했다. 최악의 경우 할인을 정하지 않을 수 있다.(미확정)

 

[Project Tree]

 

[discount/DiscountPolicy]

package hello.core.discount;

import hello.core.member.Member;

public interface DiscountPolicy {

    /**
     * @return 할인 대상 금액
     */
    int discount(Member member, int price);
}

 

[discount/FixDiscountPolicy]

package hello.core.discount;

import hello.core.member.Grade;
import hello.core.member.Member;

public class FixDiscountPolicy implements DiscountPolicy {

    private int discountFixAmount = 1000; // 1000원 할인

   @Override
    public int discount(Member member, int price) {
        return member.getGrade() == Grade.VIP ? discountFixAmount : 0;
    }
}

 

[order/Order]

package hello.core.order;

import hello.core.discount.DiscountPolicy;

public class Order {

    private Long memberId;
    private String itemName;
    private int itemPrice;
    private int discountPrice;

    public Order(Long memberId, String itemName, int itemPrice, int discountPrice) {
        this.memberId = memberId;
        this.itemName = itemName;
        this.itemPrice = itemPrice;
        this.discountPrice = discountPrice;
    }

    public int calculatePrice() {
        return itemPrice - discountPrice;
    }

    public Long getMemberId() {
        return memberId;
    }

    public void setMemberId(Long memberId) {
        this.memberId = memberId;
    }

    public String getItemName() {
        return itemName;
    }

    public void setItemName(String itemName) {
        this.itemName = itemName;
    }

    public int getItemPrice() {
        return itemPrice;
    }

    public void setItemPrice(int itemPrice) {
        this.itemPrice = itemPrice;
    }

    public int getDiscountPrice() {
        return discountPrice;
    }

    public void setDiscountPrice(int discountPrice) {
        this.discountPrice = discountPrice;
    }

    @Override
    public String toString() {
        return "Order{" +
                "memberId=" + memberId +
                ", itemName='" + itemName + '\'' +
                ", itemPrice=" + itemPrice +
                ", discountPrice=" + discountPrice +
                '}';
    }
}

 

[order/OrderService]

package hello.core.order;

public interface OrderService {
    Order createOrder(Long memberId, String itemName, int itemPrice);
}

 

[order/OrderServiceImpl]

package hello.core.order;

import hello.core.discount.DiscountPolicy;
import hello.core.discount.FixDiscountPolicy;
import hello.core.member.Member;
import hello.core.member.MemberRepository;
import hello.core.member.MemoryMemberRepository;

public class OrderServiceImpl implements OrderService {
    private final MemberRepository memberRepository = new MemoryMemberRepository();
    private final DiscountPolicy discountPolicy = new FixDiscountPolicy();

    @Override
    public Order createOrder(Long memberId, String itemName, int itemPrice) {
        Member member = memberRepository.findById(memberId);
        int discountPrice = discountPolicy.discount(member, itemPrice);
        
        return new Order(memberId, itemName, itemPrice, discountPrice);
    }
}

해당 설계는 꽤 괜찮은 설계이다. 할인 정책이나, 주문자의 회원조회 등의 기능들이 변경되더라도

유연하게 변경 가능하며, OrderService자체는 변경되지 않는다.