#30 jpa basic: jpql - function

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

@@ -0,0 +1,78 @@
+package com.hello.jpa.query;
+
+import com.hello.jpa.query.entity.Member;
+import com.hello.jpa.query.entity.MemberType;
+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 Function {
+
+    public static void main(String[] args) {
+        EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello");
+
+        EntityManager em = emf.createEntityManager();
+
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+
+        try {
+            Team team = new Team();
+            team.setName("team");
+            em.persist(team);
+
+            Member member = new Member();
+            member.setName("member");
+            member.setAge(10);
+            member.setTeam(team);
+            member.setMemberType(MemberType.ADMIN);
+
+            em.persist(member);
+
+            Member member2 = new Member();
+            member2.setName("hello world");
+            member2.setAge(70);
+            member2.setTeam(team);
+            member2.setMemberType(MemberType.USER);
+
+            em.persist(member2);
+
+            em.flush();
+            em.clear();
+
+//            String query = "select concat('a', 'b') from Member m";
+//            String query = "select substring(m.name, 2, 3) from Member m";
+//            String query = "select locate('he', m.name) from Member m";
+//            String query = "select size(t.members) from Team t";
+//            String query = "select function('group_concat', m.name) from Member m";
+            String query = "select group_concat(m.name) from Member m";
+
+            List<String> result = em.createQuery(
+                            query,
+                            String.class
+                    )
+                    .getResultList();
+
+//            List<Integer> result = em.createQuery(
+//                            query,
+//                            Integer.class
+//                    )
+//                    .getResultList();
+
+            result.forEach(System.out::println);
+
+            tx.commit();
+        } catch (Exception e) {
+            tx.rollback();
+            e.printStackTrace();
+        } finally {
+            em.close();
+        }
+
+        emf.close();
+    }
+}

hello-jpa/src/main/java/com/hello/jpa/query/dialect/MyH2Dialect.java

@@ -0,0 +1,12 @@
+package com.hello.jpa.query.dialect;
+
+import org.hibernate.dialect.H2Dialect;
+import org.hibernate.dialect.function.StandardSQLFunction;
+import org.hibernate.type.StandardBasicTypes;
+
+public class MyH2Dialect extends H2Dialect {
+
+    public MyH2Dialect() {
+        registerFunction("group_concat", new StandardSQLFunction("group_concat", StandardBasicTypes.STRING));
+    }
+}

hello-jpa/src/main/resources/META-INF/persistence.xml

@@ -49,7 +49,7 @@
             <property name="javax.persistence.jdbc.password" value=""/>
             <property name="javax.persistence.jdbc.url" value="jdbc:h2:tcp://localhost/~/test"/>
 <!--            <property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:~/testdb"/>-->
-            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
+            <property name="hibernate.dialect" value="com.hello.jpa.query.dialect.MyH2Dialect"/>
 
             <!-- 옵션 -->
             <property name="hibernate.show_sql" value="true"/>