#30 jpa basic: jpql - join

hello-jpa/src/main/java/com/hello/jpa/query/Join.java

@@ -0,0 +1,78 @@
+package com.hello.jpa.query;
+
+import com.hello.jpa.query.entity.Member;
+import com.hello.jpa.query.entity.Team;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.Persistence;
+import java.util.List;
+
+public class Join {
+
+    public static void main(String[] args) {
+        EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello");
+
+        EntityManager em = emf.createEntityManager();
+
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+
+        try {
+            for (int i = 0; i < 10; i++) {
+                Team team = new Team();
+                team.setName("team" + i);
+                em.persist(team);
+
+                Member member = new Member();
+                member.setName("member" + i);
+                member.setAge(i);
+                member.setTeam(team);
+
+                em.persist(member);
+            }
+
+            em.flush();
+            em.clear();
+
+            List<Member> result = em.createQuery(
+                            "select m from Member m inner join m.team t",
+                            Member.class
+                    )
+                    .getResultList();
+
+            List<Member> result2 = em.createQuery(
+                            "select m from Member m left outer join m.team t",
+                            Member.class
+                    )
+                    .getResultList();
+
+            List<Member> result3 = em.createQuery(
+                            "select m from Member m, Team t",
+                            Member.class
+                    )
+                    .getResultList();
+
+            List<Member> result4 = em.createQuery(
+                            "select m from Member m left join m.team t on t.name='team2'",
+                            Member.class
+                    )
+                    .getResultList();
+
+            List<Member> result5 = em.createQuery(
+                            "select m from Member m left join Team t on m.name = t.name",
+                            Member.class
+                    )
+                    .getResultList();
+
+            tx.commit();
+        } catch (Exception e) {
+            tx.rollback();
+        } finally {
+            em.close();
+        }
+
+        emf.close();
+    }
+}

hello-jpa/src/main/java/com/hello/jpa/query/entity/Member.java

@@ -11,10 +11,23 @@ public class Member {
     private String name;
     private int age;
 
-    @ManyToOne
+    @ManyToOne(fetch = FetchType.LAZY)
     @JoinColumn(name = "team_id")
     private Team team;
 
+    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 int getAge() {
         return age;
     }

hello-jpa/src/main/java/com/hello/jpa/query/entity/Team.java

@@ -18,6 +18,14 @@ public class Team {
     @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;
     }