Querydsl - 순수 JPA와 Querydsl 사용하기

✔ 순수 JPA 리포지토리와 Querydsl

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기존 JPA방식 Repository

    public void save(Member member){
        em.persist(member);
    }

    public Optional<Member> findById(Long id){
        Member findMember = em.find(Member.class, id);
        return Optional.ofNullable(findMember);
    }
    public List<Member> findAll(){
        return em.createQuery("select m from Member m",Member.class)
                .getResultList();
    }
	public List<Member> findByUserName(String username){
        return em.createQuery("select m from Member m where m.username = :username",Member.class)
                .setParameter("username",username)
                .getResultList();
    }

querydsl 방식

	public List<Member> findAll_Querydsl(){
        return queryFactory
                .selectFrom(member)
                .fetch();
    }

	public List<Member> findByUserName_Querydsl(String username){
        return queryFactory
                .selectFrom(member)
                .where(member.username.eq(username))
                .fetch();
    }

✔ 동적쿼리 Builder 적용

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조회를 하기위한 DTO를 생성해준다. 그 후에 querydsl을 사용하기 위해서 QMemberTeamDto를 만들어 준다.@QueryProjection 을 사용하면 해당 DTO가 Querydsl을 의존하게 된다. 이런 의존이 싫으면, 해당 에노테이션을 제거하고, Projection.bean(), fields(), constructor() 을 사용하면 된다.

MemberTeamDto

@Data
public class MemberTeamDto {
    private Long memberId;
    private String username;
    private int age;
    private Long teamId;
    private String teamName;

    @QueryProjection
    public MemberTeamDto(Long memberId, String username, int age, Long teamId, String teamName) {
        this.memberId = memberId;
        this.username = username;
        this.age = age;
        this.teamId = teamId;
        this.teamName = teamName;
    }
}

builder방식 조회 동적 쿼리

public List<MemberTeamDto> searchByBuilder(MemberSearchCondition condition){

        BooleanBuilder builder = new BooleanBuilder();
        if (hasText(condition.getUsername())) {
            builder.and(member.username.eq(condition.getUsername()));
        }
        if(hasText(condition.getTeamName())){
            builder.and(team.name.eq(condition.getTeamName()));
        }
        if(condition.getAgeGoe() != null) {
            builder.and(member.age.goe(condition.getAgeGoe()));
        }
        if (condition.getAgeLoe() != null) {
            builder.and(member.age.loe(condition.getAgeLoe()));
        }

        return queryFactory
                .select(new QMemberTeamDto(
                        member.id,
                        member.username,
                        member.age,
                        team.id,
                        team.name
                ))
                .from(member)
                .leftJoin(member.team, team)
                .where(builder)
                .fetch();

    }

✔ 동적쿼리 Where 적용

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where문에 파라미터를 사용한 예제 : 이름과 팀명, 그리고 나이를 ageGoe보다 크고 ageLoe보다 낮은 회원 검색. 정보가 null일 수도 있다.

파라미터를 이용한 조회 동적 쿼리

 public List<MemberTeamDto> search(MemberSearchCondition condition){
        return queryFactory
                .select(new QMemberTeamDto(
                        member.id,
                        member.username,
                        member.age,
                        team.id,
                        team.name
                ))
                .from(member)
                .leftJoin(member.team, team)
                .where(usernameEq(condition.getUsername()),
                        teamNameEq(condition.getTeamName()),
                        ageGoe(condition.getAgeGoe()),
                        ageLoe(condition.getAgeLoe())
                )
                .fetch();
    }

usernameEq,teamNameEq,ageGoe,ageLoe 파라미터 메서드

    private BooleanExpression usernameEq(String username) {
        return hasText(username) ? member.username.eq(username) : null;
    }

    private BooleanExpression teamNameEq(String teamName) {
        return hasText(teamName) ? team.name.eq(teamName) : null;
    }

    private BooleanExpression ageGoe(Integer ageGoe) {
        return ageGoe != null ? member.age.goe(ageGoe) : null;
    }

    private BooleanExpression ageLoe(Integer ageLoe) {
        return ageLoe != null ? member.age.loe(ageLoe) : null;
    }

이런식으로 파라미터 병합도 가능하다.

    public List<Member> searchMember(MemberSearchCondition condition){
        return queryFactory
                .selectFrom(member)
                .from(member)
                .leftJoin(member.team, team)
                .where(usernameEq(condition.getUsername()),
                        teamNameEq(condition.getTeamName()),
                        ageBetween(condition.getAgeLoe(),condition.getAgeLoe()))
                .fetch();
    }

병합 메서드

    private BooleanExpression ageBetween(int ageLoe, int ageGoe){
        return ageGoe(ageLoe).and(ageGoe(ageGoe));
    }

✔ 조회 API 컨트롤러 개발

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샘플 데이터 추가

@Profile("local")
@Component
@RequiredArgsConstructor
public class initMember {

    private final InitMemberService initMemberService;

    @PostConstruct
    public void init(){
        initMemberService.init();
    }
    @Component
    static class InitMemberService{
        @PersistenceContext
        private EntityManager em;

        @Transactional
        public void init(){
            Team teamA = new Team("teamA");
            Team teamB = new Team("teamB");
            em.persist(teamA);
            em.persist(teamB);

            for(int i=0; i<100; i++){
                Team selectedTeam = i%2 ==0 ? teamA : teamB;
                em.persist(new Member("member"+1,i,selectedTeam));
            }
        }
    }
}

동적 쿼리 조회 컨트롤러 및 테스트 결과

@GetMapping("/v1/members")
    public List<MemberTeamDto> searchMemberV1(MemberSearchCondition condition) {
        return memberJpaRepository.search(condition);
    }

api test툴 postman으로 조회를 해보면 teamB이면서 31살보다 많고 40살보다 적은 조건(파라미터)을 추가했을때 결과가 잘 나온다