회원 도메인 개발

1. 회원 엔티티
1) 회원 등급
- src/main/java/hello/core/member/Grade.java

package hello.core.member;

public enum Grade {

    BASIC
  , VIP

}

2) 회원 엔티티
- src/main/java/hello/core/member/Member.java

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;
    }

}

2. 회원 저장소
1) 회원 저장소 인터페이스
- src/main/java/hello/core/member/MemberRepository.java

package hello.core.member;

public interface MemberRepository {

    void save(Member member);

    Member findById(Long memberId);
    
}

2) 메모리 회원 저장소 구현체
- src/main/java/hello/core/member/MemoryMemberRepository.java

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);
    }

}

데이터베이스 확정이 되지 않았을 때, 가장 단순한 메모리 저장소를 구현하여 개발 진행

* 참고
HashMap은 동시성 이슈가 발생할 수 있으니, 이런 경우 ConcurrentHashMap을 사용한다.


3. 회원 서비스
1) 회원 서비스 인터페이스
- src/main/java/hello/core/member/MemberService.java

package hello.core.member;

public interface MemberService {

    void join(Member member);

    Member findMember(Long memberId);

}

2) 회원 서비스 구현체
구현체가 1개일 때, 관례상 서비스 이름 뒤에 Impl을 붙여 클래스명을 짓는다.

- src/main/java/hello/core/member/MemberServiceImpl.java

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);
    }

}

참고링크 : https://www.inflearn.com/course/%EC%8A%A4%ED%94%84%EB%A7%81-%ED%95%B5%EC%8B%AC-%EC%9B%90%EB%A6%AC-%EA%B8%B0%EB%B3%B8%ED%8E%B8?cid=325969

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