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+# 4~5섹션
+
+### 비즈니스 요구사항
+
+- 데이터 : 회원ID, 이름
+- 기능 : 회원 등록, 조회
+- 데이터 저장소 선정X
+- MemberService 클래스, MemberRepository 인터페이스, Memory 구현체
+
+- hello-spring > src > main > java > hello.hello_spring > domain 패키지 > **Member 클래스** 생성
+    
+    ```java
+    package hello.hello_spring.domain;
+    
+    public class Member {
+        private Long id;
+        private String name;
+    
+        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;
+        }
+    }
+    ```
+    
+- hello-spring > src > main > java > hello.hello_spring > repository 패키지 > **MemberRepository 인터페이스** 생성
+    
+    ```java
+    package hello.hello_spring.repository;
+    
+    import hello.hello_spring.domain.Member;
+    
+    import java.util.List;
+    import java.util.Optional;
+    
+    public interface MemberRepository {
+        Member save(Member member); //회원 저장
+        Optional<Member> findById(Long id);
+        Optional<Member> findByName(String name);
+        List<Member> findAll(); //모든 회원 리스트 반환
+    }
+    // Optional => null값 처리 방법
+    ```
+    
+- hello-spring > src > main > java > hello.hello_spring > repository  > **MemoryMemberRepository 클래스** 생성
+    
+    ```java
+    package hello.hello_spring.repository;
+    
+    import hello.hello_spring.domain.Member;
+    
+    import java.util.*;
+    
+    public class MemoryMemberRepository implements MemberRepository {
+    
+        private static Map<Long, Member> store = new HashMap<>();
+        private static long sequence = 0L;
+    
+        @Override
+        public Member save(Member member) { //id 셋팅 후 저장
+            member.setId(++sequence);
+            store.put(member.getId(), member);
+            return member;
+        }
+    
+        @Override
+        public Optional<Member> findById(Long id) {
+            return Optional.ofNullable(store.get(id)); //id가 널값이어도 반환
+        }
+    
+        @Override
+        public Optional<Member> findByName(String name) {
+            return store.values().stream()
+                    .filter(member -> member.getName().equals(name))
+                    .findAny(); //이름 하나 찾으면 반환
+        }
+    
+        @Override
+        public List<Member> findAll() {
+            return new ArrayList<>(store.values());
+        }
+            
+        public void clearStore() {
+            store.clear();
+        } // test 실행마다 메모리 비우기 용도
+    }
+    
+    ```
+    
+- ***test case 작성*** (src > test > java > hello.hellospring > repository 패키지 > MemoryMemberRepositoryTest 생성)
+    
+    ```java
+    package hello.hellospring.repositroy;
+    
+    import hello.hellospring.domain.Member;
+    import hello.hellospring.repository.MemoryMemberRepository;
+    import org.assertj.core.api.Assertions;
+    import org.junit.jupiter.api.AfterEach;
+    import org.junit.jupiter.api.Test;
+    
+    import java.util.List;
+    import java.util.Optional;
+    
+    class MemoryMemberRepositoryTest {
+    
+        MemoryMemberRepository repository = new MemoryMemberRepository();
+    
+        @AfterEach // test 실행마다 store 비우기(실행순서 상관없이 한번에 실행확인 가능)
+        public void afterEach() {
+            repository.clearStore();
+        } 
+    
+        @Test
+        public void save() {
+            Member member = new Member();
+            member.setName("spring");
+    
+            repository.save(member);
+    
+            Member result = repository.findById(member.getId()).get();
+    //      System.out.println("result = " + (result == member));
+    //      Assertions.assertEquals(member, result);
+            Assertions.assertThat(member).isEqualTo(result);
+        }
+    
+        @Test
+        public void findByName() {
+            Member member1 = new Member();
+            member1.setName("spring1");
+            repository.save(member1);
+    
+            Member member2 = new Member();
+            member2.setName("spring2");
+            repository.save(member2);
+    
+            Member result = repository.findByName("spring1").get();
+    
+            Assertions.assertThat(result).isEqualTo(member1);
+        }
+    
+        @Test
+        public void findAll() {
+            Member member1 = new Member();
+            member1.setName("spring1");
+            repository.save(member1);
+    
+            Member member2 = new Member();
+            member2.setName("spring2");
+            repository.save(member2);
+    
+            List<Member> result = repository.findAll();
+    
+            Assertions.assertThat(result.size()).isEqualTo(2);
+        }
+    }
+    
+    ```
+    
+
+- 회원 서비스 개발 (src > test > java > hello.hellospring > service 패키지 > MemberService 생성 )
+    
+    ```java
+    package hello.hellospring.service;
+    
+    import hello.hellospring.domain.Member;
+    import hello.hellospring.repository.MemberRepository;
+    import hello.hellospring.repository.MemoryMemberRepository;
+    
+    import java.util.List;
+    import java.util.Optional;
+    
+    public class MemberService {
+    
+        private final MemberRepository memberRepository = new MemoryMemberRepository();
+    
+        /*
+        * 회원 가입
+        */
+        public Long join(Member member) {
+            //같은 이름이 있는 중복 회원 X
+            /*Optional<Member> result = memberRepository.findByName(member.getName()); //ctrl+alt+v로 변수도입기능 사용가능
+            result.ifPresent(m -> {
+                throw new IllegalStateException("이미 존재하는 회원입니다."); 
+            });*/
+    		        //Optional 메소드들 중 하나 여서 아래 매소드 안의 코드처럼 바로 작성가능
+    
+            valiateDuplicateMember(member); //중복회원관리 (ctrl+t로 단축키검색 -> ctrl+alt+m => 자동 메소드생성
+            memberRepository.save(member);
+            return member.getId();
+        }
+    
+        private void valiateDuplicateMember(Member member) {
+            memberRepository.findByName(member.getName())
+                    .ifPresent(m -> {
+                        throw new IllegalStateException("이미 존재하는 회원입니다.");
+                    });
+        }
+    
+        /*
+         * 전체 회원 조회
+         */
+        public List<Member> findMembers(){
+            return memberRepository.findAll();
+        }
+    
+        public Optional<Member> findOne(Long memberId){
+            return memberRepository.findById(memberId);
+        }
+    }
+    
+    ```
+    
+- 회원 서비스 테스트 (클래스 이름 잡고 ctrl+shift+t ⇒ 자동 test 클래스 생성)
+    
+    ```java
+    package hello.hellospring.service;
+    
+    import hello.hellospring.domain.Member;
+    import hello.hellospring.repository.MemoryMemberRepository;
+    import org.assertj.core.api.Assertions;
+    import org.junit.jupiter.api.AfterEach;
+    import org.junit.jupiter.api.Test;
+    
+    import static org.assertj.core.api.Assertions.*;
+    import static org.junit.jupiter.api.Assertions.*;
+    
+    class MemberServiceTest {
+    
+        MemberService memberService = new MemberService();
+        MemoryMemberRepository memberRepository = new MemoryMemberRepository();
+    
+        @AfterEach
+        public void afterEach() {
+            memberRepository.clearStore();
+        } //test 실행 후 db값 초기화
+    
+        @Test
+        void 회원가입() {
+            //given 조건
+            Member member = new Member();
+            member.setName("hello");
+    
+            //when 무엇을
+            Long saveId = memberService.join(member);
+    
+            //then 검증
+            Member findMember = memberService.findOne(saveId).get();
+            assertThat(member.getName()).isEqualTo(findMember.getName());
+            //Assertions를 static으로 변환 (alt+enter)
+        }
+    
+        @Test
+        public void 중복_회원_예외() {
+            //given
+            Member member1 = new Member();
+            member1.setName("spring");
+            Member member2 = new Member();
+            member2.setName("spring");
+    
+            //when
+            memberService.join(member1);
+            IllegalStateException e = assertThrows(IllegalStateException.class, () -> memberService.join(member2));
+            // 얘가 되야한다 -> 이게 실행될때
+            assertThat(e.getMessage()).isEqualTo("이미 존재하는 회원입니다.");
+    
+            /*try {
+                memberService.join(member2);
+                org.junit.jupiter.api.Assertions.fail(); //그냥 fail()하면 에러남
+            } catch (IllegalStateException e) {
+                assertThat(e.getMessage()).isEqualTo("이미 존재하는 회원입니다.");
+            } try_catch로 가능하지만 굳이?*/
+    
+            //then
+        }
+    
+        @Test
+        void findMembers() {
+        }
+    
+        @Test
+        void findOne() {
+        }
+    }
+    ```
+    
+    - 테스트를 같은 레퍼지토리로 사용하기 위해서 MemberService, MemberServiceTest 클래스 수정
+        
+        ```java
+        public class MemberService {
+        
+            private final MemberRepository memberRepository;
+            
+            public MemberService(MemberRepository memberRepository) {
+                this.memberRepository = memberRepository;
+            } //외부에서 넣어주도록 설정
+        ```
+        
+        ```java
+        class MemberServiceTest {
+        
+            MemberService memberService;
+            MemoryMemberRepository memberRepository;
+        
+            @BeforeEach
+            public void beforeEach() {
+                memberRepository  = new MemoryMemberRepository();
+                memberService = new MemberService(memberRepository);
+            } //테스트 실행전 마다 같은 메모리레포지토리를 가지도록 설정
+        ```
+        
+
+---
+
+### 의존관계
+
+- 회원 컨트롤러 ⇒ 회원 서비스, 회원 레포지토리를 의존
+- ***컴포넌트 스캔 방식***
+    - src > main > java > hello.hellospring > controller > MemberController 클래스 생성
+        
+        ```java
+        package hello.hellospring.controller;
+        
+        import hello.hellospring.service.MemberService;
+        import org.springframework.beans.factory.annotation.Autowired;
+        import org.springframework.stereotype.Controller;
+        
+        @Controller
+        public class MemberController {
+        
+            private final MemberService memberService;
+        
+            @Autowired //컨트롤러와 서비스를 연결(의존관계)
+            public MemberController(MemberService memberService) {
+                this.memberService = memberService;
+            }
+        }
+        /*----------------------------------------------------------------*/
+        @Service
+        public class MemberService {
+        
+            private final MemberRepository memberRepository;
+        
+            @Autowired //서비스와 레포지토리를 연결(의존)
+            public MemberService(MemberRepository memberRepository) {
+                this.memberRepository = memberRepository;
+            }
+        /*----------------------------------------------------------------*/
+        @Repository
+        public class MemoryMemberRepository implements MemberRepository {
+        
+        ```
+        
+        - 스프링이 인식할 수 있도록 @Controller, @Service, @Repository 클래스명 위에 작성 
+        (컴포넌트 스캔 방식)
+        - 의존관계는 @Autowired로 연결
+
+- ***자바 코드로 직접 스프링 빈 등록***
+    - @Service, (sevice)@Autowired, @Repository 제거
+    - main > java > hello.hellospring > service > SpringConfig 클래스 생성
+        
+        ```java
+        package hello.hellospring.service;
+        
+        import hello.hellospring.repository.MemberRepository;
+        import hello.hellospring.repository.MemoryMemberRepository;
+        import org.springframework.context.annotation.Bean;
+        import org.springframework.context.annotation.Configuration;
+        
+        @Configuration //스프링이 뜰때 읽음
+        public class SpringConfig {
+        
+            @Bean //스프링 빈에 등록
+            public MemberService memberService() {
+                return new MemberService(memberRepository()); //서비스 -> 레포지토리
+            }
+        
+            @Bean
+            public MemberRepository memberRepository() {
+                return new MemoryMemberRepository();
+            }
+        }
+        ```
+        
+        - 나중에 db연결 시 간편한 방식
+- DI 방식
+    
+    ```java
+    // 1. 생성자 주입 (권장-의존관계가 동적으로 변할 일 없음)
+    @Controller
+    public class MemberController {
+    
+        private final MemberService memberService;
+    
+        @Autowired
+        public MemberController(MemberService memberService) {
+            this.memberService = memberService;
+        }
+    }
+    
+    // 2. 필드 주입 (별로)
+    @Controller
+    public class MemberController {
+    
+        @Autowired private MemberService memberService;
+    }
+    
+    // 3. 셋터 주입 (메소드가 public로 열려있음)
+    @Controller
+    public class MemberController {
+    
+        private MemberService memberService;
+    
+        @Autowired
+        public void setMemberController(MemberService memberService) {
+            this.memberService = memberService;
+        }
+    }
+    ```
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