[QueryDSL] 실무 활용 - 순수 JPA와 Querydsl

[ 순수 JPA 리포지토리와 QueryDSL ]

1. 순수 JPA 리포지토리

• 순수 JPA 리포지토리

@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();
    }
}

• 테스트 코드

@SpringBootTest
@Transactional
class MemberJpaRepositoryTest {

    @Autowired
    EntityManager em;
    
    @Autowired
    MemberJpaRepository memberJpaRepository;
    
    @Test
    public void basicTest() {
        Member member = new Member("member1", 10);
        memberJpaRepository.save(member);
        
        Member findMember = memberJpaRepository.findById(member.getId()).get();
        assertThat(findMember).isEqualTo(member);
        
        List<Member> result1 = memberJpaRepository.findAll();
        assertThat(result1).containsExactly(member);
        
        List<Member> result2 = memberJpaRepository.findByUsername("member1");
        assertThat(result2).containsExactly(member);
    }
}

2. QueryDSL

• 순수 JPA 리포지토리 - QueryDSL 추가

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();
}

• QueryDSL 테스트 추가

@Test
public void basicQuerydslTest() {
    Member member = new Member("member1", 10);
    memberJpaRepository.save(member);
    
    Member findMember = memberJpaRepository.findById(member.getId()).get();
    assertThat(findMember).isEqualTo(member);
    
    List<Member> result1 = memberJpaRepository.findAll_Querydsl();
    assertThat(result1).containsExactly(member);
    
    List<Member> result2 = memberJpaRepository.findByUsername_Querydsl("member1");
    assertThat(result2).containsExactly(member);
}

• JPAQueryFactory 스프링 빈 등록

@Bean
JPAQueryFactory jpaQueryFactory(EntityManager em) {
    return new JPAQueryFactory(em);
}

위와 같이 JPAQueryFacotry를 스프링 빈으로 등록해서 주입받아 사용해도 된다.

---

[ 동적 쿼리와 성능 최적화 조회 - Builder 사용 ]

1. MemberTeamDto - 조회 최적화용 DTO 추가

@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 team, String teamName) {
        this.memberId = memberId;
        this.username = username;
        this.age = age;
        this.teamId = teamId;
        this.teamName = teamName;
    }
}

• @QueryProjection을 추가했다.
• QMemberTeamDto를 생성하기 위해 ./gradlew compileQuerydsl 실행하기!

📌 참고

@QueryProjection을 사용하면 해당 DTO가 Querydsl을 의존하게 된다.
이런 의존이 싫으면 해당 어노테이션을 제거하고, Projection.bean(), fields(), constructor() 사용하기!

2. 회원 검색 조건

@Data
public class MemberSearchCondition {

    //회원명, 팀명, 나이(ageGoe, ageLoe)
    private String username;
    private String teamName;
    private Integer ageGoe;
    private Integer ageLoe;
}

3. Builder를 사용한 예제

//Builder 사용
//회원명, 팀명, 나이(ageGoe, ageLoe)
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();
}

4. 조회 예제 테스트

@Test
public void searchTest() {

    Team teamA = new Team("teamA");
    Team teamB = new Team("teamB");
    em.persist(teamA);
    em.persist(teamB);
    
    Member member1 = new Member("member1", 10, teamA);
    Member member2 = new Member("member2", 20, teamA);
    Member member3 = new Member("member3", 30, teamB);
    Member member4 = new Member("member4", 40, teamB);
    
    em.persist(member1);
    em.persist(member2);
    em.persist(member3);
    em.persist(member4);
    
    MemberSearchCondition condition = new MemberSearchCondition();
    condition.setAgeGoe(35);
    condition.setAgeLoe(40);
    condition.setTeamName("teamB");
    
    List<MemberTeamDto> result = memberJpaRepository.searchByBuilder(condition);
    assertThat(result).extracting("username").containsExactly("member4");
}

---

[ 동적 쿼리와 성능 최적화 조회 - Where절 파라미터 사용 ]

//회원명, 팀명, 나이(ageGoe, ageLoe)
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);
}

참고: where 절에 파라미터 방식을 사용하면 조건 재사용 가능

//where 파라미터 방식은 이런식으로 재사용이 가능하다.
public List<Member> findMember(MemberSearchCondition condition) {
    return queryFactory
            .selectFrom(member)
            .leftJoin(member.team, team)
            .where(usernameEq(condition.getUsername()),
                    teamNameEq(condition.getTeamName()),
                    ageGoe(condition.getAgeGoe()),
                    ageLoe(condition.getAgeLoe()))
            .fetch();
}

Builder를 사용하는 것보다 Where절에 파라미터 방식을 사용하는 것이 가독성이 좋다.

---

[ 조회 API 컨트롤러 개발 ]

1. 프로파일 설정

편리한 데이터 확인을 위해 샘플 데이터를 추가해보자.
이때 샘플 데이터 추가가 테스트 케이스 실행에 영향을 주지 않도록 프로파일을 설정하자.

• src/main/resources/application.yml

spring:
  profiles:
    active: local

• src/test/resources/application.yml

spring:
  profiles:
    active: test

이렇게 분리하면 main 소스코드와 테스트 소스 코드 실행시 프로파일을 분리할 수 있다.

2. 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
        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" + i, i, selectedTeam));
            }
        }
    }
}

InitMemberService의 init() 안의 내용을 바로 @PostConstruct 어노테이션이 달린 init() 안에 바로 넣지 않고 굳이 분리하는 이유는 @PostConstruct와 @Transactional을 동시에 붙일 수 없기 때문이다!

강의에서는 이렇게만 말씀하셨는데 찾아보니까 어떤 분이 질문을 남기셔서 링크 첨부!

3. 조회 컨트롤러

@RestController
@RequiredArgsConstructor
public class MemberController {

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