간단한 회원 관리 예제3-회원 서비스 개발

hello-spring\src\main\java\hello\hellospring\service\MemberService.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();

    /**
     * 회원가입
     **/

    public Long join(Member member) {
        // 같은 이름이 있는 중복 회원X
        validateDuplicateMember(member);
        memberRepository.save(member);
        return member.getId();
    }

    private void validateDuplicateMember(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);
    }
}