인프런 커뮤니티 질문&답변

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[질문 템플릿]
1. 강의 내용과 관련된 질문인가요? (예/아니오) 예
2. 인프런의 질문 게시판과 자주 하는 질문에 없는 내용인가요? (예/아니오) 예
3. 질문 잘하기 메뉴얼을 읽어보셨나요? (예/아니오) 예

[질문 내용]

22: 10 초에서는 Team과 Member의 join fetch 를 진행하면 result = 3 의 결과가 나오는데 저는 계속해서 result = 2의 결과가 나와서 질문드립니다. 최신 버전으로 인해서 jpa 최적화 방식의 변화가 생겨서 그런 것인지 아니면 제가 실수한 것인지 궁금합니다.

JpaMain 실행결과:

디비 상태:

package jpql;

import jakarta.persistence.*;

import java.util.List;

public class JpaMain {

    public static void main(String[] args) {

        EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello");
        EntityManager em = emf.createEntityManager();

        EntityTransaction tx = em.getTransaction();
        tx.begin();

        try{

            Team teamA = new Team();
            teamA.setName("teamA");
            em.persist(teamA);

            Team teamB = new Team();
            teamB.setName("teamB");
            em.persist(teamB);

            Member member1 = new Member();
            member1.setUsername("회원1");
            member1.setAge(10);
            member1.setTeam(teamA);
            em.persist(member1);

            Member member2 = new Member();
            member2.setUsername("회원2");
            member2.setAge(10);
            member2.setTeam(teamA);
            em.persist(member2);

            Member member3 = new Member();
            member3.setUsername("회원3");
            member3.setAge(10);
            member3.setTeam(teamB);
            em.persist(member3);

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

            String query = "select t from Team t join fetch t.members";
            List<Team> result = em.createQuery(query, Team.class)
                    .getResultList();

            System.out.println("result = " + result.size());

            for (Team team : result) {

                System.out.println("team = " + team.getName());
                for(Member member : team.getMembers()){
                    System.out.println("-> member = " + member.getUsername());
                }
            }

            tx.commit();
        }
        catch(Exception e){

            e.printStackTrace();
            tx.rollback();
        }

    }
}

package jpql;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.Id;
import jakarta.persistence.OneToMany;

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

@Entity
public class Team {

    @Id @GeneratedValue
    private Long id;
    private String name;

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

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

    public void setMembers(List<Member> members) {
        this.members = members;
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

 package jpql;

import jakarta.persistence.*;

@Entity
public class Member {

    @Id @GeneratedValue
    private Long id;
    private String username;
    private int age;

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

    @Enumerated(EnumType.STRING)
    private MemberType type;

    public MemberType getType() {
        return type;
    }

    public void setType(MemberType type) {
        this.type = type;
    }

    public void changeTeam(Team team) {

        this.team = team;
        team.getMembers().add(this);
    }

    public Team getTeam() {
        return team;
    }

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

    public Long getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "Member{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", age=" + age +
                '}';
    }
}