JPA - Hello, World! using Hibernate 5

The article JPA - Hello, World! using Hibernate explains how to use Hibernate v4.x. This tutorial introduces using JPA with the latest Hibernate v5.2.3. Same as the previous article, it also targets beginners who are new to Hibernate and JPA.

You need Java 1.8, Eclipse for Java EE developers and MySQL server in your system in-order to try this tutorial.

Step 1:

Create a database “javahelps” and a table “student” in MySQL.

CREATE DATABASE IF NOT EXISTS javahelps;

CREATE  TABLE javahelps.student ( 
student_id INT NOT NULL ,
student_name VARCHAR(45) NOT NULL ,
student_age INT NOT NULL ,
PRIMARY KEY (student_id) );

Step 2:

Create a new Maven project “JPAWithHibernate5” in Eclipse using the following configuration.

Group id: com.javahelps
Artifact id:  JPAWithHibernate5

Step 3:

Open the pom.xml and add the following dependencies and plugin.

<!-- Logback to print the logs generated by Hibernate -->
<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.1.7</version>
</dependency>

<!-- Core of Hibernate -->
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>5.2.3.Final</version>
</dependency>

<!-- Entity manager which is required for JPA -->
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-entitymanager</artifactId>
    <version>5.2.3.Final</version>
</dependency>

<!-- JDBC Connector for MySQL -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>6.0.4</version>
</dependency>

<!-- This plugin is used to set the Java version 1.8 -->
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.5.1</version>
    <configuration>
        <source>1.8</source>
        <target>1.8</target>
    </configuration>
</plugin>

After the modification, pom.xml should look like this:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.javahelps</groupId>
    <artifactId>JPAWithHibernate5</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <dependencies>
        <!-- Logback to print the logs generated by Hibernate -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.7</version>
        </dependency>

        <!-- Core of Hibernate -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.2.3.Final</version>
        </dependency>

        <!-- Entity manager which is required for JPA -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.2.3.Final</version>
        </dependency>

        <!-- JDBC Connector for MySQL -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.4</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <!-- This plugin is used to set the Java version 1.8 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Right click on the project and select Maven → Update Project → Click OK on the appeared dialog to apply the changes done in the pom file.

Step 4:

Create a new package “com.javahelps.jpa” in src/main/java folder.

Step 5:

Create a new class Student inside the package as shown below.

package com.javahelps.jpa;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "student")
public class Student implements Serializable {
    @Id
    @Column(name = "student_id", unique = true)
    private int id;

    @Column(name = "student_name", nullable = false)
    private String name;

    @Column(name = "student_age", nullable = false)
    private int age;

    public int getId() {
        return id;
    }

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

    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;
    }

    @Override
    public String toString() {
        return id + "\t" + name + "\t" + age;
    }
}

Step 6:

Right click on the src/main/resources folder and create a new folder META-INF.

Step 7:

Create a new file persistence.xml, in the META-INF folder and modify the content as shown below.

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
    version="2.0">
    <persistence-unit name="JavaHelps" transaction-type="RESOURCE_LOCAL">
        <!-- Persistence provider -->
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

        <!-- Entity classes -->
        <class>com.javahelps.jpa.Student</class>

        <properties>
            <!-- The JDBC URL to the database instance -->
            <property name="javax.persistence.jdbc.url"
                value="jdbc:mysql://localhost:3306/javahelps?useSSL=false&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC" />

            <!-- The database username -->
            <property name="javax.persistence.jdbc.user" value="root" />

            <!-- The database password -->
            <property name="javax.persistence.jdbc.password" value="root" />
        </properties>
    </persistence-unit>
</persistence>

In this configuration file, change the username and password of the database according to your database. With the new Hibernate and JDBC, you do not need to specify the JDBC driver in the persistence.xml file but due to a bug in JDBC Connector, the timezone configurations are required in the JDBC url.

Note: When you add the above code, replace all the & signs in the JDBC URL by &

Step 8:

Create a new Java class Main.java with main method.

Step 9:

Create an EntityManagerFactory and initialize it as shown below. The persistence unit name used to create the EntityManagerFactory, should match with the name defined in the persistence.xml file.

package com.javahelps.jpa;

import java.util.List;

import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

public class Main {
    // Create an EntityManagerFactory when you start the application.
    private static final EntityManagerFactory ENTITY_MANAGER_FACTORY = Persistence
            .createEntityManagerFactory("JavaHelps");
}

Step 10:

Add the CRUD methods to the Main class and access them from the main method as given below:

package com.javahelps.jpa;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

public class Main {
    // Create an EntityManagerFactory when you start the application.
    private static final EntityManagerFactory ENTITY_MANAGER_FACTORY = Persistence
            .createEntityManagerFactory("JavaHelps");

    public static void main(String[] args) {

        // Create two Students
        create(1, "Alice", 22);     // Alice will get an id 1
        create(2, "Bob", 20);       // Bob will get an id 2
        create(3, "Charlie", 25);   // Charlie will get an id 3

        // Update the age of Bob using the id
        upate(2, "Bob", 25);

        // Delete the Alice from database
        delete(1);

        // Print all the Students
        List<Student> students = readAll();
        if (students != null) {
            for (Student stu : students) {
                System.out.println(stu);
            }
        }

        // NEVER FORGET TO CLOSE THE ENTITY_MANAGER_FACTORY
        ENTITY_MANAGER_FACTORY.close();
    }

    /**
     * Create a new Student.
     * 
     * @param name
     * @param age
     */
    public static void create(int id, String name, int age) {
        // Create an EntityManager
        EntityManager manager = ENTITY_MANAGER_FACTORY.createEntityManager();
        EntityTransaction transaction = null;

        try {
            // Get a transaction
            transaction = manager.getTransaction();
            // Begin the transaction
            transaction.begin();

            // Create a new Student object
            Student stu = new Student();
            stu.setId(id);
            stu.setName(name);
            stu.setAge(age);

            // Save the student object
            manager.persist(stu);

            // Commit the transaction
            transaction.commit();
        } catch (Exception ex) {
            // If there are any exceptions, roll back the changes
            if (transaction != null) {
                transaction.rollback();
            }
            // Print the Exception
            ex.printStackTrace();
        } finally {
            // Close the EntityManager
            manager.close();
        }
    }

    /**
     * Read all the Students.
     * 
     * @return a List of Students
     */
    public static List<Student> readAll() {

        List<Student> students = null;

        // Create an EntityManager
        EntityManager manager = ENTITY_MANAGER_FACTORY.createEntityManager();
        EntityTransaction transaction = null;

        try {
            // Get a transaction
            transaction = manager.getTransaction();
            // Begin the transaction
            transaction.begin();

            // Get a List of Students
            students = manager.createQuery("SELECT s FROM Student s", Student.class).getResultList();

            // Commit the transaction
            transaction.commit();
        } catch (Exception ex) {
            // If there are any exceptions, roll back the changes
            if (transaction != null) {
                transaction.rollback();
            }
            // Print the Exception
            ex.printStackTrace();
        } finally {
            // Close the EntityManager
            manager.close();
        }
        return students;
    }

    /**
     * Delete the existing Student.
     * 
     * @param id
     */
    public static void delete(int id) {
        // Create an EntityManager
        EntityManager manager = ENTITY_MANAGER_FACTORY.createEntityManager();
        EntityTransaction transaction = null;

        try {
            // Get a transaction
            transaction = manager.getTransaction();
            // Begin the transaction
            transaction.begin();

            // Get the Student object
            Student stu = manager.find(Student.class, id);

            // Delete the student
            manager.remove(stu);

            // Commit the transaction
            transaction.commit();
        } catch (Exception ex) {
            // If there are any exceptions, roll back the changes
            if (transaction != null) {
                transaction.rollback();
            }
            // Print the Exception
            ex.printStackTrace();
        } finally {
            // Close the EntityManager
            manager.close();
        }
    }

    /**
     * Update the existing Student.
     * 
     * @param id
     * @param name
     * @param age
     */
    public static void upate(int id, String name, int age) {
        // Create an EntityManager
        EntityManager manager = ENTITY_MANAGER_FACTORY.createEntityManager();
        EntityTransaction transaction = null;

        try {
            // Get a transaction
            transaction = manager.getTransaction();
            // Begin the transaction
            transaction.begin();

            // Get the Student object
            Student stu = manager.find(Student.class, id);

            // Change the values
            stu.setName(name);
            stu.setAge(age);

            // Update the student
            manager.persist(stu);

            // Commit the transaction
            transaction.commit();
        } catch (Exception ex) {
            // If there are any exceptions, roll back the changes
            if (transaction != null) {
                transaction.rollback();
            }
            // Print the Exception
            ex.printStackTrace();
        } finally {
            // Close the EntityManager
            manager.close();
        }
    }
}

Step 11:

Run the project and check the output.

Step 12:
To avoid unnecessary console output caused by Hibernate debug logs, create a new file logback.xml in src/main/resources folder with the following content.

<?xml version="1.0" encoding="UTF-8"?>
<configuration debug="false">

    <contextListener class="ch.qos.logback.classic.jul.LevelChangePropagator" />

    <!-- Format the log output -->
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n
            </pattern>
        </encoder>
    </appender>

    <!-- Set the application log level to INFO -->
    <root level="INFO">
        <appender-ref ref="STDOUT" />
    </root>

    <!-- Set log level of Hibernate to WARN level -->
    <logger name="org.hibernate">
        <level value="WARN" />
    </logger>

</configuration>

Find the Maven project at Git Hub.

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