[QueryDsl] `JPA Repository + QueryDsl`로 동적 쿼리 & API 개발 구축 (Builder or 다중 Where 메서드)

순수 JPA Repository를 구축하여 QueryDsl 을 추가해본다.

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QueryDsl을 위한 JPAQueryFactory는 2가지 방법으로 주입 가능하다.

1. @Bean으로 등록 후 @Autowired
2. 생성자 주입

@Bean
    JPAQueryFactory jpaQueryFactory(EntityManager em) {
            return new JPAQueryFactory(em);
            }
// 1. @Bean으로 등록 후 주입받기

//  @Autowired  
//  JPAQueryFactory queryFactory;
or

// 2. 생성자 주입받기 ( new)
//public MemberJpaRepository(EntityManager em) {
//        this.em = em;
//        this.queryFactory = new JPAQueryFactory(em);
//}

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JPA Repository 구축

일반 JPA이기 때문에 findAll, findById 등등 수동 생성

예시로 findAll만 작성했다.

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Team과 Member를 함께 검색하여 받기 위한 검색 Dto 제작 (@Query)

@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;
 }
}

@QueryProjection을 선언하면 추후 compile시에 지정된 경로에 QMemberTeamDto 생성자가 생긴다.

다만 class 자체가 QueryDsl에 너무도 종속적이라 추후 QueryDsl을 제거하거나 여러 변수가 있을 때, 문제가 생길 수 있다.

그럼 다른 방법으로 Projection.bean(), fields(), constructor() 중 골라서 쓰면 된다.

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@Repository
public class MemberJpaRepository {

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

    //순수 JPA
    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();
    }
}

QueryDsl로 검색 기능하는 동적 코드 작성

1. builder 사용

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.as("memberId"),
        member.username,
        member.age,
        team.id.as("teamId"),
        team.name.as("teamName")))
        .from(member)
        .leftJoin(member.team, team)
        .where(builder)
        .fetch();
        }

다중 where 메서드를 사용해서 만들기

public List<MemberTeamDto> search(MemberSearchCondition condition) {
        return queryFactory
                .select(new QMemberTeamDto(
                        member.id.as("memberId"),
                        member.username,
                        member.age,
                        team.id.as("teamId"),
                        team.name.as("teamName")))
                .from(member)
                .leftJoin(member.team, team)
                .where(
                        usernameEq(condition.getUsername()),
                        teamNameEq(condition.getTeamName()),
                        ageGoe(condition.getAgeGoe()),
                        ageLoe(condition.getAgeLoe())
        //null이면 자동으로 where 조건에서 빠진다.
                ).fetch();
    }



    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;
    }

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