Querydsl

https://tecoble.techcourse.co.kr/post/2021-08-08-basic-querydsl/

세팅법

https://docs.google.com/document/d/1j0jcJ9EoXMGzwAA2H0b9TOvRtpwlxI5Dtn3sRtuXQas/edit#heading=h.vfy9wirpglmx

Spring Data JPA랑 같이 사용하기

• public interface PostCustomRepository

  • 직접 구현할 PostCustomRepository를 생성

• public class PostCustomRepositoryImpl implements PostCustomRepository

  • 위 인터페이스를 구현하는 클래스에서 QueryDSL 작성
  • 반드시 Impl로 끝나야함

  @Repository
  public class PostCustomRepositoryImpl implements PostCustomRepository {
  
      private final JPAQueryFactory jpaQueryFactory;
  
      public PostCustomRepositoryImpl(JPAQueryFactory jpaQueryFactory) {
          this.jpaQueryFactory = jpaQueryFactory;
      }
  
      @Override
      public List<Post> findAllInnerFetchJoin() {
          return jpaQueryFactory.selectFrom(post)
              .innerJoin(post.comments)
              .fetchJoin()
              .fetch();
      }
  
      @Override
      public List<Post> findAllInnerFetchJoinWithDistinct() {
          return jpaQueryFactory.selectFrom(post)
              .distinct()
              .innerJoin(post.comments)
              .fetchJoin()
              .fetch();    
      }
  }
  

• public interface PostRepository extends JpaRepository<Post, Long>, PostCustomRepository

  • SpringDataJPA를 사용하는 (JpaRepository를 상속하는) 인터페이스에서 PostCustomRepository를 상속

• spring data jpa와 사용하지 않는다면 그냥 인터페이스를 사용하지 않고 직접 클래스에서 정의할 수도 있다

• 아래는 join 없는 단순 JPQL을 QueryDSL로 변경한 예시이다

  • select
  • from
  • where
    • and
  • gt
  • orderBy
  • desc

@BeforeEach
    void before(){
        Team teamA = new Team("teamA");
        Team teamB = new Team("teamB");
        teamRepository.save(teamA);
        teamRepository.save(teamB);

        Member member1 = new Member("member11", 10, teamA);
        Member member2 = new Member("member12", 15, teamB);
        Member member3 = new Member("member21", 20, teamB);
        Member member4 = new Member("member22", 25, teamB);
        memberRepository.save(member1);
        memberRepository.save(member2);
        memberRepository.save(member3);
        memberRepository.save(member4);
    }

    @Test
    void queryDslTest2(){
        List<String> memberNames = jpaQueryFactory.select(member.username).from(member).
                where(member.username.contains("2").and(member.age.gt(15))).
                orderBy(member.username.desc()).
                fetch();

        assertThat(memberNames.get(0)).isEqualTo("member22");
        assertThat(memberNames.get(1)).isEqualTo("member21");
    }

Join 문법

기본 Join

• 기본 join은 innerJoin이다