스프링기본3_비즈니스 요구사항과 설계를 통한 개발예제 작성

비즈니스 요구사항과 설계 / 개발 1차

(1) 회원

1.회원을 가입하고 조회할 수 있다.
2.회원은 일반과 vip 두가지 등급이 있다.
3.회원 데이터는 자체DB를 구축할 수 있고, 외부 시스템과 연동할 수 있다(미확정)

• Member.java

package springbasic.core.member;

public class Member {
    private Long id;
    private String name;
    private Grade grade;

    public Member(Long id, String name, Grade grade) {
        this.id = id;
        this.name = name;
        this.grade = grade;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Grade getGrade() {
        return grade;
    }

    public void setGrade(Grade grade) {
        this.grade = grade;
    }
}

• Grade.java

package springbasic.core.member;

public enum Grade {
    BASIC,
    VIP
}

• MemberRepository.java

package springbasic.core.member;

public interface MemberRepository {

    void save(Member member);

    Member findById(Long memberId);
}

• MemoryMemberRepository.java

package springbasic.core.member;

import java.util.HashMap;
import java.util.Map;

public class MemoryMemberRepository implements MemberRepository{

    private static Map<Long, Member> store = new HashMap<>();

    @Override
    public void save(Member member) {
        store.put(member.getId(), member);
    }

    @Override
    public Member findById(Long memberId) {
        return store.get(memberId);
    }
}

• MemberService.java

package springbasic.core.member;

import org.springframework.stereotype.Service;

public interface MemberService {

    void join(Member member);

    Member findMember(Long memberId);
}

• MemberServiceImpl.java

package springbasic.core.member;

public class MemberServiceImpl implements MemberService{
    private final MemberRepository memberRepository = new MemoryMemberRepository();

    @Override
    public void join(Member member) {
        memberRepository.save(member);
    }

    @Override
    public Member findMember(Long memberId) {
        return memberRepository.findById(memberId);
    }
}

• MemberServiceTest.java

package springbasic.core.member;

import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;

public class MemberServiceTest {

    MemberService memberService = new MemberServiceImpl();

    @Test
    void join(){
        //given
        Member member = new Member(1L,"memberA",Grade.VIP);

        //when
        memberService.join(member);
        Member findMember = memberService.findMember(1L);

        //then
        Assertions.assertThat(member).isEqualTo(findMember);
    }
}

---

(2) 주문과 할인정책

1.회원은 상품을 주문할 수 있다.
2.회원등급에 따라 할인정책을 적용할 수 있다.
3.할인정책은 모든 vip는 1000원을 할인해주는 고정 금액 할인을 적용해달라(나중에 변경될 수 있다)
4.할인정책은 변경가능성이 높다. 회사의 기본 할인 정책을 아직 정하지 못했고, 오픈 직전까지 고민을 미루고 싶다. 최악의 경우 할인을 적용하지 않을 수도 있다(미확정)

• DiscountPolicy.java

package springbasic.core.discount;

import springbasic.core.member.Member;

public interface DiscountPolicy {

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

• FixDiscountPolicy.java

package springbasic.core.discount;

import springbasic.core.member.Grade;
import springbasic.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;
        }
    }
}

• Order.java

package springbasic.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 +
                '}';
    }
}

• OrderService.java

package springbasic.core.order;

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

• OrderServiceImpl.java

package springbasic.core.order;

import springbasic.core.discount.DiscountPolicy;
import springbasic.core.discount.FixDiscountPolicy;
import springbasic.core.member.Member;
import springbasic.core.member.MemberRepository;
import springbasic.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);
    }
}

• OrderServiceTest

package springbasic.core.order;

import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import springbasic.core.member.Grade;
import springbasic.core.member.Member;
import springbasic.core.member.MemberService;
import springbasic.core.member.MemberServiceImpl;

public class OrderServiceTest {

    MemberService memberService = new MemberServiceImpl();
    OrderService orderService = new OrderServiceImpl();

    @Test
    void createOrder(){

        //given
        Long memberId = 1L;
        Member member = new Member(memberId,"memverA", Grade.VIP);
        memberService.join(member);

        //when
        Order order = orderService.createOrder(memberId,"itemA",10000);

        //then
        Assertions.assertThat(order.getDisCountPrice()).isEqualTo(1000);
    }
}

---

• 정리
  -> 설계에 따른 개발은 완성!
  --> But 과연 좋은 객체 지향 설계의 5대 원칙을 다 지켜서 개발된 것일까?
  ---> 소스의 변경이 있을 떄 [OCP 개방-폐쇄 원칙]이 과연 지켜질까?