Bael 2532 hibernate aggregate functions (#6266)

* BAEL-2532 Hibernate Aggregate Functions

* BAEL-2532 Deleting created Student POJO

persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/pojo/Student.java

@@ -9,15 +9,43 @@ import javax.persistence.Id;
 public class Student {
 
     @Id
-    @GeneratedValue (strategy = GenerationType.SEQUENCE)
+    @GeneratedValue(strategy = GenerationType.SEQUENCE)
     private long studentId;
 
+    private String name;
+
+    private int age;
+
+    public Student() {
+    }
+
+    public Student(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
     public long getStudentId() {
         return studentId;
     }
 
-    public void setStudent_id(long studentId) {
+    public void setStudentId(long studentId) {
         this.studentId = studentId;
     }
-    
+
+    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;
+    }
+
 }

persistence-modules/hibernate5/src/test/java/com/baeldung/hibernate/aggregatefunctions/AggregateFunctionsIntegrationTest.java

@@ -0,0 +1,87 @@
+package com.baeldung.hibernate.aggregatefunctions;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.IOException;
+
+import org.hibernate.HibernateException;
+import org.hibernate.Session;
+import org.hibernate.Transaction;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import com.baeldung.hibernate.HibernateUtil;
+import com.baeldung.hibernate.pojo.Student;
+
+public class AggregateFunctionsIntegrationTest {
+
+    private static Session session;
+    private static Transaction transaction;
+
+    @BeforeClass
+    public static final void setup() throws HibernateException, IOException {
+        session = HibernateUtil.getSessionFactory()
+            .openSession();
+        transaction = session.beginTransaction();
+
+        Student jonas = new Student("Jonas", 22);
+        session.save(jonas);
+
+        Student sally = new Student("Sally", 20);
+        session.save(sally);
+
+        Student simon = new Student("Simon", 25);
+        session.save(simon);
+
+        Student raven = new Student("Raven", 21);
+        session.save(raven);
+
+        Student sam = new Student("Sam", 23);
+        session.save(sam);
+
+    }
+
+    @AfterClass
+    public static final void teardown() {
+        if (session != null) {
+            transaction.rollback();
+            session.close();
+        }
+    }
+
+    @Test
+    public void whenMaxAge_ThenReturnValue() {
+        int maxAge = (int) session.createQuery("SELECT MAX(age) from Student")
+            .getSingleResult();
+        assertThat(maxAge).isEqualTo(25);
+    }
+
+    @Test
+    public void whenMinAge_ThenReturnValue() {
+        int minAge = (int) session.createQuery("SELECT MIN(age) from Student")
+            .getSingleResult();
+        assertThat(minAge).isEqualTo(20);
+    }
+
+    @Test
+    public void whenAverageAge_ThenReturnValue() {
+        Double avgAge = (Double) session.createQuery("SELECT AVG(age) from Student")
+            .getSingleResult();
+        assertThat(avgAge).isEqualTo(22.2);
+    }
+
+    @Test
+    public void whenCountAll_ThenReturnValue() {
+        Long totalStudents = (Long) session.createQuery("SELECT COUNT(*) from Student")
+            .getSingleResult();
+        assertThat(totalStudents).isEqualTo(5);
+    }
+
+    @Test
+    public void whenSumOfAllAges_ThenReturnValue() {
+        Long sumOfAllAges = (Long) session.createQuery("SELECT SUM(age) from Student")
+            .getSingleResult();
+        assertThat(sumOfAllAges).isEqualTo(111);
+    }
+}