[QueryDSL] 활용 (JPA + QueryDSL)

 

 

 

실제로 애플리케이션을 설계할 때는 Repository 계층을 만들고 Repository를 통해 데이터베이스와 상호작용한다.

먼저 Spring Data JPA 기술 없이 순수 JPA와 QueryDSL 만 사용해서 Repository를 설계해보자.

 

 

@Repository
public class MemberJpaRepository {
    private final EntityManager em;
    private final JPAQueryFactory queryFactory;

    public MemberJpaRepository(EntityManager em) {
        this.em = em;
        this.queryFactory = new JPAQueryFactory(em);
    }

    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();
    }

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


}

 

 

QueryDSL 기술을 사용하면 JPA 로만 작성할 때 보다 좀 더 간편하게 작성할 수 있다.

추가로 BooleanBuilder를 사용해 동적 쿼리를 구현하자.

 

 

    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();
    }

 

 

DTO를 사용해 Member와 Team 정보를 함께 조회하는 예시이다.

 

MemberSearchCondition 객체를 만들어 검색 조건을 간단하게 표현했고, StringUtils의 hasText 함수를 사용해 문자열이 null인지 확인한 후 BooleanBuilder를 만들어준다.

 

쿼리를 작성할 때 builder를 추가해야 함을 잊지 말자.

 

 

    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();
    }
    private BooleanExpression usernameEq(String username) {
        return isEmpty(username) ? null : member.username.eq(username);
    }
    private BooleanExpression teamNameEq(String teamName) {
        return isEmpty(teamName) ? null : team.name.eq(teamName);
    }
    private BooleanExpression ageGoe(Integer ageGoe) {
        return ageGoe == null ? null : member.age.goe(ageGoe);
    }
    private BooleanExpression ageLoe(Integer ageLoe) {
        return ageLoe == null ? null : member.age.loe(ageLoe);
    }

 

 

where 다중 파라미터를 사용해서 동적 쿼리를 구현해도 된다.