Hibernate Maven MySQL Hello World example (XML Mapping)

In this tutorial, we will try to write a small hello world program using Hibernate, MySQL and Maven. We will create a Java project using Maven and will then try to add Hibernate on it.

Following are the tools and technologies used in this project.

1. Java JDK 5 or above
2. Eclipse IDE 3.2 or above
3. Maven 3.0 or above
4. Hibernate 3.0 or above
5. MySQL 5.0 or above

1. Database Creation

For this tutorial, we will create a simple table “employe” in MySQL. Use following script to create the table.

CREATE TABLE `employee` (
	`id` BIGINT(10) NOT NULL AUTO_INCREMENT,
	`firstname` VARCHAR(50) NULL DEFAULT NULL,
	`lastname` VARCHAR(50) NULL DEFAULT NULL,
	`birth_date` DATE NOT NULL,
	`cell_phone` VARCHAR(15) NOT NULL,
	PRIMARY KEY (`id`)
)
COLLATE='latin1_swedish_ci'
ENGINE=InnoDB
ROW_FORMAT=DEFAULT
AUTO_INCREMENT=606

Thus, following will be the connection string to connect with MySQL.

Connection URL:	jdbc:mysql://localhost:3306/tutorial
DB Username:	root
DB Password:	<your mysql password>

2. Generate Maven Java project compatible with Eclipse

Open a command prompt and execute following code to generate a Maven Java project.

mvn archetype:generate \
	-DgroupId=net.viralpatel.hibernate \
	-DartifactId=HibernateHelloWorldXML \
	-DarchetypeArtifactId=maven-archetype-quickstart \
	-DinteractiveMode=false

Once you execute above command, a project “HibernateHelloWorldXML” is created. Note that this is a Java project which already has folder structures compatible to Maven.

Once this is done, we will convert it to be compatible with Eclipse. For that executes following command on command prompt.

mvn eclipse:eclipse

3. Import project in Eclipse

Open Eclipse and import the above Java project.

File > Import… > General > Existing Projects into Workspace > Choose above Java project

Once imported, the folder structure will look like following:

Important:

In case you get following error after importing project in Eclipse:

If you are getting this Hibernate Maven Repo error, then you need to define M2_REPO environment variable in eclipse pointing to your local maven repository.

Goto Window > Preferences… > Java > Build Path > Classpath Variables > Define new variable M2_REPO pointing to your local maven repository.

Once you will define this variable and rebuild the project, the above error will go.

4. Add Hibernate Dependency to Maven pom.xml

Add following dependencies to Maven pom.xml.

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>net.viralpatel.hibernate</groupId>
  <artifactId>HibernateHelloWorldXML</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>HibernateHelloWorldXML</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.10</version>
    </dependency>
    <dependency>
      <groupId>org.hibernate</groupId>
      <artifactId>hibernate</artifactId>
      <version>3.2.6.ga</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

Once we have added these dependencies, we will execute following command so that maven will download required Jar files and add the same to eclipse classpath.

mvn eclipse:eclipse

The above step is not mandatory. If you have Maven plugin for Eclipse installed in your IDE (Latest eclipse comes with this plugin built-in) you can just enable Maven dependencies by doing
Right click on project > Maven > Enable Dependency Management.

5. Add Hibernate Configuration XML

Now our project setup is ready. We will add following Hibernate configuration xml file in /src/main/resources folder. Note that this folder is not present in your project structure.

Create a source folder:
Right click on Project > New > Source Folder > Give folder name “/src/main/resources/” and click Finish.

Copy following file in your project.

File: /src/main/resources/hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
 
<hibernate-configuration>
    <session-factory>
        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/tutorial</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>
        
        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>
        
        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
        
        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">false</property>
        
        <property name="hbm2ddl.auto">validate</property>
 
        <mapping resource="net/viralpatel/hibernate/Employee.hbm.xml"/>
 		
 		 
    </session-factory>
</hibernate-configuration>

One thing we need to make sure in Eclipse is that the Java build path must reflect **/*.xml.
Right click on project > Properties > Java Build Path > Source > Add **/*.xml as follow:

6. Add Java source code

File: /src/main/java/net/viralpatel/hibernate/Employee.java

package net.viralpatel.hibernate;

import java.sql.Date;

public class Employee {

	private Long id;
	
	private String firstname;
	
	private String lastname;
	
	private Date birthDate;
	
	private String cellphone;

	public Employee() {
		
	}
	
	public Employee(String firstname, String lastname, Date birthdate, String phone) {
		this.firstname = firstname;
		this.lastname = lastname;
		this.birthDate = birthdate;
		this.cellphone = phone;
		
	}
	
	// Getter and Setter methods

}

Above is the Employee POJO class that we will use to fetch data from Employee table. This Java class will be mapped by Hiberate with Employee table. Note that we have define two constructors first default and second with arguements. The second constructor is optional. But note that you must define a default (No-arguement) constructor in your mapping class.

File: /src/main/java/net/viralpatel/hibernate/HibernateUtil.java

package net.viralpatel.hibernate;
 
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
 
public class HibernateUtil {
 
    private static final SessionFactory sessionFactory = buildSessionFactory();
 
    private static SessionFactory buildSessionFactory() {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            return new Configuration()
            		.configure()
                    .buildSessionFactory();
        } catch (Throwable ex) {
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
 
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

As discussed in previous article Introduction to Hibernate framework, we have to create SessionFactory instance in order to communicate with Database in Hibernate. We will use a Utility class called HibernateUtil to instantiate SessionFactory.

File: /src/main/java/net/viralpatel/hibernate/Employee.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="net.viralpatel.hibernate">

    <class name="Employee" table="EMPLOYEE">
 		<id name="id" column="ID">
            <generator class="native"/>
        </id>
        <property name="firstname" />
        <property name="lastname" column="lastname"/>
        <property name="birthDate" type="date" column="birth_date"/>
        <property name="cellphone" column="cell_phone"/>
	</class>

</hibernate-mapping>

7. CRUD operations in Hibernate

Let us see the basic CRUD operation in Hibernate. We will use Employee table for this.

7.1 Writing (Create) data in Hibernate

Following is the code snippet that insert a row in database.

private static Employee save(Employee employee) {
	SessionFactory sf = HibernateUtil.getSessionFactory();
	Session session = sf.openSession();
	session.beginTransaction();

	Long id = (Long) session.save(employee);
	employee.setId(id);
		
	session.getTransaction().commit();
		
	session.close();

	return employee;
}

...
...
...

// Call the save() method to insert a record in database.
System.out.println("******* WRITE *******");
Employee empl = new Employee("Jack", "Bauer", new Date(System.currentTimeMillis()), "911");
empl = save(empl);

7.2 Reading (Read) data in Hibernate

Below code snippet demos read functionality in Hibernate. Note that there are two methods one to list all the employees and other to read details about just one.

private static List list() {
	SessionFactory sf = HibernateUtil.getSessionFactory();
	Session session = sf.openSession();

	List employees = session.createQuery("from Employee").list();
	session.close();
	return employees;
}
private static Employee read(Long id) {
	SessionFactory sf = HibernateUtil.getSessionFactory();
	Session session = sf.openSession();

	Employee employee = (Employee) session.get(Employee.class, id);
	session.close();
	return employee;
}

7.3 Updating (Update) data in Hibernate

Following is the code snippet to update a record in Hibernate.

private static Employee update(Employee employee) {
	SessionFactory sf = HibernateUtil.getSessionFactory();
	Session session = sf.openSession();

	session.beginTransaction();

	session.merge(employee);

	session.getTransaction().commit();

	session.close();
	return employee;

}

7.4 Remove (Delete) data in Hibernate

Following is code snippet to remove a record in Hibernate.

private static void delete(Employee employee) {
	SessionFactory sf = HibernateUtil.getSessionFactory();
	Session session = sf.openSession();

	session.beginTransaction();

	session.delete(employee);

	session.getTransaction().commit();

	session.close();
}

We have created a file Main.java which will test all these functionality. Following is the complete source code of Main.java.
File: /src/main/java/net/viralpatel/hibernate/Main.java

package net.viralpatel.hibernate;

import java.sql.Date;
import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;


public class Main {

	public static void main(String[] args) {
		
		
		// Read
		System.out.println("******* READ *******");
		List employees = list();
		System.out.println("Total Employees: " + employees.size());
		
		
		// Write
		System.out.println("******* WRITE *******");
		Employee empl = new Employee("Jack", "Bauer", new Date(System.currentTimeMillis()), "911");
		empl = save(empl);
		empl = read(empl.getId());
		System.out.printf("%d %s %s \n", empl.getId(), empl.getFirstname(), empl.getLastname());
		
		
		
		// Update
		System.out.println("******* UPDATE *******");
		Employee empl2 = read(1l); // read employee with id 1
		System.out.println("Name Before Update:" + empl2.getFirstname());
		empl2.setFirstname("James");
		update(empl2);	// save the updated employee details
		
		empl2 = read(1l); // read again employee with id 1
		System.out.println("Name Aftere Update:" + empl2.getFirstname());
		
		
		// Delete
		System.out.println("******* DELETE *******");
		delete(empl); 
		Employee empl3 = read(empl.getId());
		System.out.println("Object:" + empl3);
	}
	
	

	private static List list() {
		SessionFactory sf = HibernateUtil.getSessionFactory();
		Session session = sf.openSession();

		List employees = session.createQuery("from Employee").list();
		session.close();
		return employees;
	}
	private static Employee read(Long id) {
		SessionFactory sf = HibernateUtil.getSessionFactory();
		Session session = sf.openSession();

		Employee employee = (Employee) session.get(Employee.class, id);
		session.close();
		return employee;
	}
	private static Employee save(Employee employee) {
		SessionFactory sf = HibernateUtil.getSessionFactory();
		Session session = sf.openSession();

		session.beginTransaction();

		Long id = (Long) session.save(employee);
		employee.setId(id);
		
		session.getTransaction().commit();
		
		session.close();

		return employee;
	}

	private static Employee update(Employee employee) {
		SessionFactory sf = HibernateUtil.getSessionFactory();
		Session session = sf.openSession();

		session.beginTransaction();

		session.merge(employee);
		
		session.getTransaction().commit();
		
		session.close();
		return employee;

	}

	private static void delete(Employee employee) {
		SessionFactory sf = HibernateUtil.getSessionFactory();
		Session session = sf.openSession();
		
		session.beginTransaction();
		
		session.delete(employee);
		
		session.getTransaction().commit();
		
		session.close();
	}
	
}

8. Final project structure

Once you have created all these source files, your project structure should look like following. Note that we have removed the default App.java and AppTest.java generated by Maven as we dont these files.

9. Execute project

Execute the Main.java class and see output.

******* READ *******
Total Employees: 200
******* WRITE *******
201 Jack Bauer 
******* UPDATE *******
Name Before Update:Paula
Name Aftere Update:James
******* DELETE *******
Object:null

That’s All Folks

Today we saw how to write our first Hibernate hello world example using XML Configuration. We used Maven to generate Java project and added Hibernate dependencies into it. Also we saw how to do different CRUD operations in Hibernate.

Download Source

HibernateHelloWorldXML.zip (8 kb)