[Spring] 주문과 할인 도메인 개발

 

 

먼저 할인(discount)와  주문(order)의 패키지 생성을 해야한다.

 

discount

Interface : DiscountPolicy

Class : FixDiscountPolitcy

 

order

Interface : OrderService

Class : Order, OrderServiceImpl

 

먼저 DiscountPolicy.java 를 생성

package hello.core.discount;

import hello.core.member.Member;

public interface DiscountPolicy {

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

 

그 다음, FixDiscountPolicy.java를 생성한다.

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) {
        if(member.getGrade() == Grade.VIP) {
            return discountFixAmount;
        } else {
            return 0;
        }
    }
}

 

그 다음,  Order.java 를 만들어준다.

 

package hello.core.order;

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 +
                '}';
    }
}

 

생성자와 Getter And Setter, toString은 ALT + INSERT를 이용하면 간편하게 만들 수 있다.

 

 

그 다음으로, OrderService를 만든다.

 

package hello.core.order;

public interface OrderService {

    // 주문 결과를 반환
    Order createOrder(Long memberId, String itemName, int itemPrice);


}

 

OrderServiceImpl.java

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); // SRD를 잘 지킨 형식
        
        return new Order(memberId, itemName, itemPrice, discountPrice);
    }
}

 

discountPolicy.discount()는 딱 할인율 구하는 자기 본연의 역할만 하므로 단일 책임 원칙(SRD)에 부합한다.