인프런 커뮤니티 질문&답변

안녕하세요. 다대일 양방향 관계에 대해 질문 드립니다.

Member 엔티티와 Team 엔티티가 다대일 양방향 맵핑 되어있고, 

package hellojpa;

import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;
@Entity
public class Member {
    @Id
    @GeneratedValue
    @Column(name= "MEMBER_ID")
    private Long id;

    private String name;

    private int age;

    @OneToMany(mappedBy = "member")
    private List<Order> orders = new ArrayList<Order>();

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "TEAM_ID")
    private Team team;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void setTeam(Team team) {
        this.team = team;
        team.getMembers().add(this);
    }
}

package hellojpa;

import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;

@Entity
public class Team {
    @Id
    @GeneratedValue
    @Column(name = "TEAM_ID")
    private Long id;

    private String name;

    @OneToMany(mappedBy = "team",fetch = FetchType.LAZY)
    private List<Member> members = new ArrayList<>();

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public List<Member> getMembers() {
        return members;
    }

    public void setName(String name) {
        this.name = name;
    }
}

팀에서 getMembers 메소드를 통하여 해당 팀에 소속된 멤버들을 조회할 때

public class hellojpa {
    public static void main(String[] args) {
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello");
        EntityManager em = emf.createEntityManager();
        EntityTransaction transaction = em.getTransaction();
        transaction.begin();
        try {
            Member member =new Member();
            member.setName("member1");
            member.setAge(20);

            Team team = new Team();
            team.setName("team a");
            em.persist(team);

            member.setTeam(team);
            em.persist(member);

            Member member2 = new Member();
            member2.setName("member222");
            member2.setTeam(team);
            em.persist(member2);

            em.flush();
            em.clear();

            List<Member> memberList = em.find(Team.class, team.getId()).getMembers();
            for (Member member1 : memberList) {
                System.out.println(member1.getName());
            }
        } catch (Exception e) {
            transaction.rollback();
        } finally {
            em.close();
        }
        emf.close();
    }
}

저는

select

        member0_.MEMBER_ID

        members0_.TEAM_ID 

        members0_.age

        members0_.name

    from

        Member members0_ 

    where

        members0_.TEAM_ID=?

이러한 쿼리가 생성될 것으로 예상했습니다. 

하지만 실제 쿼리가 나간것을 확인해보니

select

        members0_.TEAM_ID as team_id4_0_0_,

        members0_.MEMBER_ID as member_i1_0_0_,

        members0_.MEMBER_ID as member_i1_0_1_,

        members0_.age as age2_0_1_,

        members0_.name as name3_0_1_,

        members0_.TEAM_ID as team_id4_0_1_ 

    from

        Member members0_ 

    where

        members0_.TEAM_ID=?

select문에서 특정 컬럼들이 중복되어 표시되는데(bold표시), 혹시 이렇게 표시되는게 정상적인 것인지 혹은 맵핑 과정에서 실수가 있었던지 궁금하여 질문 드립니다!