인프런 스프링 핵심 원리-기본편 #2 스프링 핵심원리 1 - 예제 만들기

회원 도메인 개발

 

 Member 도메인

package hello.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;
    }
}

Alt + Insert를 사용해서 생성자와 Getter Setter을 편리하게 만들 수 있다. 

 

package hello.core.member;

public enum Grade {
    BASIC,
    VIP
}

Grade enum Class

 

package hello.core.member;

public interface MemberRepository {
    void save(Member member);

    Member findById(Long memberId);
}

 

package hello.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);
    }
}

MemberRepository의 구현 클래스인 MemoryMemberRepository

 

 

package hello.core.member;

public interface MemberService {
    void join(Member member);

    Member findMember(Long memberId);
}

 

MemberService의 인터페이스

package hello.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);
    }
}

MemberService의 구현체

 

 

회원 도메인 실행과 테스트

 

package hello.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);
    }
}

main 클래스에 실제로 실행하여 저장해보기

package hello.core;

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

public class MemberApp {
    public static void main(String[] args) {
        MemberService memberService = new MemberServiceImpl();
        Member member = new Member(1L, "memberA", Grade.VIP);
        memberService.join(member);

        Member findMember = memberService.findMember(1L);
        System.out.println("new member = " + member.getName());
        System.out.println("find member = " + findMember.getName());
    }
}

MemberServiceTest

 

 

 

 

주문과 할인 도메인 설계

Order.java

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 +
                '}';

    }
}

 

OrderService Interface

package hello.core.order;

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

}

 

OrderServceImplement

package hello.core.order;

import hello.core.discount.DiscountPolicy;
import hello.core.discount.FixDiscountPolicy;
import hello.core.discount.RateDiscountPolicy;
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();
    private final DiscountPolicy discountPolicy = new RateDiscountPolicy();

    @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);
    }
}

 

주문 테스트

 

package hello.core.order;

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

public class OrderServiceTest {
    MemberService memberService = new MemberServiceImpl();
    OrderService orderService = new OrderServiceImpl();

    @Test
    void createOrder(){
        Long memberId = 1L;
        Member member  = new Member(memberId, "memberA", Grade.VIP);
        memberService.join(member);

        Order order = orderService.createOrder(memberId, "itemA", 10000);
        Assertions.assertThat(order.getDiscountPrice()).isEqualTo(1000);
    }
}

VIP인 경우, 할인된 가격인 discountPrice가 1000으로 계산되는 것을 알 수 있다. 

 

이때 OrderServiceImpl에서, 

memberRepository와 discountPolicy가 인터페이스, 구현체에 동시에 의존하는 것을 알 수 있다. 

이런 방식은 DIP에 어긋나는 방식이므로

다음 강의에서 '생성자 주입'이라는 것을 이용해 이를 해결해보겠다.