[QueryDSL] 예제 도메인 모델 및 동작확인

예제 도메인 모델

• Member

package study.querydsl.entity;

import jakarta.persistence.*;
import lombok.*;

import static jakarta.persistence.FetchType.*;

@Entity
@Getter @Setter
@NoArgsConstructor(access = AccessLevel.PROTECTED)
@ToString(of = {"id", "username", "age"})
public class Member {
    @Id
    @GeneratedValue
    @Column(name = "member_id")
    private Long id;
    private String username;
    private int age;

    @ManyToOne(fetch = LAZY)
    @JoinColumn(name = "team_id")
    private Team team;

    public Member(String username) {
        this(username, 0);
    }

    public Member(String username, int age) {
        this(username, age, null);
    }

    public Member(String username, int age, Team team) {
        this.username = username;
        this.age = age;
        if (team != null) {
            changeTeam(team);
        }
    }

    private void changeTeam(Team team) {
        this.team = team;
        team.getMembers().add(this);
    }


}

• Team

package study.querydsl.entity;

import jakarta.persistence.*;
import lombok.*;

import java.util.ArrayList;
import java.util.List;

@Entity
@Getter
@Setter
@NoArgsConstructor(access = AccessLevel.PROTECTED)
@ToString(of = {"id", "name"})
public class Team {

    @Id
    @GeneratedValue
    @Column(name = "team_id")
    private Long id;

    private String name;

    @OneToMany(mappedBy = "team")
    private List<Member> members = new ArrayList<>();

    public Team(String name) {
        this.name = name;
    }
}

• @Setter는 실무에서 사용하지 않는 것을 권장
• changeTeam() 메소드를 통해 양방향 연관관계 처리
• 기본 생성자 레벨은 PROTECTED로 설정
• Member과 Team은 양방향 관계이지만 Member.team이 주인이라 외래키 값 변경 Team.members는 읽기만 가능

테스트

package study.querydsl.entity;

import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.annotation.Commit;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

import static org.junit.jupiter.api.Assertions.*;

@SpringBootTest
@Transactional
class MemberTest {

    @PersistenceContext
    EntityManager em;

    @Test
    public void testEntity() {
        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);

        //초기화
        em.flush();
        em.clear();

        List<Member> members = em.createQuery("select m from Member m", Member.class)
                .getResultList();

        for (Member member : members) {
            System.out.println("member = " + member);
            System.out.println("member.team = " + member.getTeam());
        }
    }
}

• 프린트문으로 출력하는 것 보다는 assert 이용하는 것이 좋음.