Querydsl - Spring Data JPA와 함께 쓸 수 있는 사용자 Repository, 페이징 처리

MemberRepositoryCustom

package study.querydsl.repository;

import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import study.querydsl.dto.MemberSearchCondition;
import study.querydsl.dto.MemberTeamDto;

import java.util.List;

public interface MemberRepositoryCustom {
    List<MemberTeamDto> search(MemberSearchCondition condition);
    Page<MemberTeamDto> searchPageSimple(MemberSearchCondition condition, Pageable pageable);
    Page<MemberTeamDto> searchPageComplex(MemberSearchCondition condition, Pageable pageable);
}

• inferface 생성 후 구현체 메소드 작성
• 페이징을 할때는 Page라는 객체에 <반환 타입>을 매핑해주고 매개변수로 Pageable을 사용한다.

MemberRepositoryCustom

package study.querydsl.repository;

import com.querydsl.core.QueryResults;
import com.querydsl.core.types.dsl.BooleanExpression;
import com.querydsl.jpa.impl.JPAQueryFactory;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.Pageable;
import org.springframework.util.StringUtils;
import study.querydsl.dto.MemberSearchCondition;
import study.querydsl.dto.MemberTeamDto;
import study.querydsl.dto.QMemberTeamDto;

import java.util.List;

import static study.querydsl.entity.QMember.member;
import static study.querydsl.entity.QTeam.team;

public class MemberRepositoryImpl implements MemberRepositoryCustom {

    private final JPAQueryFactory queryFactory;

    public MemberRepositoryImpl(JPAQueryFactory queryFactory) {
        this.queryFactory = queryFactory;
    }

    @Override
    public List<MemberTeamDto> search(MemberSearchCondition condition) {
        return queryFactory
                .select(new QMemberTeamDto(
                        member.id.as("memberId"),
                        member.username,
                        member.age,
                        member.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())
                )
                .fetch();
    }

    @Override
    public Page<MemberTeamDto> searchPageSimple(MemberSearchCondition condition, Pageable pageable) {
        QueryResults<MemberTeamDto> queryResults = queryFactory
                .select(new QMemberTeamDto(
                        member.id.as("memberId"),
                        member.username,
                        member.age,
                        member.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())
                )
                .offset(pageable.getOffset())
                .limit(pageable.getPageSize())
                .fetchResults();

        List<MemberTeamDto> content = queryResults.getResults();
        long total = queryResults.getTotal();


        return new PageImpl<>(content, pageable, total);
    }

    @Override
    public Page<MemberTeamDto> searchPageComplex(MemberSearchCondition condition, Pageable pageable) {
        List<MemberTeamDto> content = getMemberTeamDtos(condition, pageable);
        long total = getTotal(condition);

        return new PageImpl<>(content, pageable, total);
    }

    private List<MemberTeamDto> getMemberTeamDtos(MemberSearchCondition condition, Pageable pageable) {
        List<MemberTeamDto> content = queryFactory
                .select(new QMemberTeamDto(
                        member.id.as("memberId"),
                        member.username,
                        member.age,
                        member.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())
                )
                .offset(pageable.getOffset())
                .limit(pageable.getPageSize())
                .fetch();
        return content;
    }

    private long getTotal(MemberSearchCondition condition) {
        long total = queryFactory
                .selectFrom(member)
                .leftJoin(member.team, team)
                .where(
                        usernameEq(condition.getUsername()),
                        teamNameEq(condition.getTeamName()),
                        ageGoe(condition.getAgeGoe()),
                        ageLoe(condition.getAgeLoe())
                )
                .fetchCount();
        return total;
    }

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

    private BooleanExpression teamNameEq(String teamName) {
        return StringUtils.hasText(teamName) ? member.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;
    }
}

• 구현 클래스 작성
  
  
• searchPageSimple()은 offset(), limit(), fetchResults()로 마무리해준다.
  • offset()은 페이지를 의미하고
  • limit()는 몇개 씩 보여줄지 정할 수 있고
  • fetchResults()는 list와 count를 동시에 해준다.
    • result가 searchPageSimple() 호출한 return 결과 값이라면
    • result.getSize() : totalCount
    • result.getContent() : list
  • return은 new PageImpl<>(content, pageable, total)으로 하면 된다.
    PageImpl 클래스가 Page클래스에 상속 받아져 있기때문이다.
    
    
• searchPageComplex()은 list와 count 쿼리를 분리한 것이고 리팩토링을 하여 getMemberTeamDtos(), getTotal()로 분리한 것이다.

MemberRepository

package study.querydsl.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import study.querydsl.entity.Member;

import java.util.List;

@Repository
public interface MemberRepository extends JpaRepository<Member, Long>, MemberRepositoryCustom {

    List<Member> findByUsername(String username);
}

• MemberRepository는 JpaRepository와 MemberRepositoryCustom를 상속받으면 Spring Data JPA와 QueryDsl를 같이 쓸 수 있는 것이다.
• 그렇지만 이렇게 사용자 Repository를 만드는 것이 정답은 아니다. QueryDsl만 있는 Repository를 따로 만들어서 사용해도 무관하다.