Hibernate Configuration And SessionFactory Instantiation

This Hiberate tutorial is part of the Hiberate introduction series. We will see how to configure the Hiberate options and instantiate SessionFactory.

Hibernate provides different options to create a SessionFactory instance; SessionFactory is used for creating multiple lightweight instances of Session object, which in turn enables database operations. We need not worry about the performance side of creating/destroying those Hibernate Session instances; Because they’re lightweight components.

On the other side the process of creating instance for Hibernate SessionFactory is an expensive operation. So we need to exercise caution while instantiating Hibernate SessionFactory. We can choose to create the instance through a singleton design pattern.

Hibernate Configuration options

• Database connection settings: These attributes comprises the driver class, url of jdbc connection, username and password for connected schema.
• Hibernate Dialect: As we know, Hibernate is database-agnostic framework, at some point, hibernate needs to use database specific, extended or native SQL, so hibernate uses dialect configuration to know which database you’re using so that it can switch to the database specific SQL generator code. If you’ve omitted this entry, hibernate would provide default one based on the database driver provided.
• Hibernate Session Context: Tracking of session against different contexts can help achieve Create, Read, Update and Delete operations. Mainly, permitted values are Thread or its corresponding class or JTA for managed container or its corresponding class. Transaction demarcation concept and all of these different context are to be discussed later on, in a separate tutorials.

Configure Hibernate with hibernate.cfg.xml

• Configure Hibernate by using hibernate.cfg.xml: Hibernate can be configured using hibernate.cfg.xml file. This file must be located under the resource folder. Refer the Hibernate example project structure below.

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://192.168.1.102:3306/javapapers</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>

        <!-- SQL dialect -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <!-- Specify session context -->
        <property name="hibernate.current_session_context_class">org.hibernate.context.internal.ThreadLocalSessionContext</property>

    </session-factory>

</hibernate-configuration>

Configure Hibernate with hibernate.properties

Similar to hibernate.cfg.xml, hibernate.properties file should defined for all of these mandatory entries. hibernate.properties file should be located in the application classpath.

hibernate.properties

hibernate.connection.driver_class = com.mysql.jdbc.Driver
hibernate.connection.url = jdbc:mysql://localhost:3306/javapapers
hibernate.connection.username = root
hibernate.connection.password = root
hibernate.dialect = org.hibernate.dialect.MySQLDialect
hibernate.current_session_context_class=thread

With hibernate.properties the will project look like:

Hibernate Example Application

Create an example Hibernate application and you need to setup the development environment. Follow the linked tutorial to setup the project and put the following Java class file and run it.

App.java

package com.javapapers;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class App {
 public static void main(String[] args) throws FileNotFoundException, IOException{
 configureUsingHibernatePropertiesFile();
 }

 public static void configureUsingHibernateConfigXMLFile(){
 // Create configuration instance
 Configuration configuration = new Configuration();

 // Pass hibernate configuration file
 configuration.configure("hibernate.cfg.xml");

 // Since version 4.x, service registry is being used
 ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().
 applySettings(configuration.getProperties()).build(); 

 // Create session factory instance
 SessionFactory factory = configuration.buildSessionFactory(serviceRegistry);

 // Get current session
 Session session = factory.getCurrentSession();

 // Begin transaction
 session.getTransaction().begin();

 // Print out all required information
 System.out.println("Session Is Opened :: "+session.isOpen());
 System.out.println("Session Is Connected :: "+session.isConnected()); 

 // Commit transaction
 session.getTransaction().commit();

 System.exit(0);
 }

 public static void configureUsingHibernatePropertiesFile() throws IOException{
 // Create configuration instance
 Configuration configuration = new Configuration();

 // Create properties file
 Properties properties = new Properties();
 properties.load(Thread.currentThread().getContextClassLoader().getResourceAsStream("hibernate.properties"));
 // Pass hibernate properties file
 configuration.setProperties(properties);
 // Since version 4.x, service registry is being used
 ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().
 applySettings(configuration.getProperties()).build(); 

 // Create session factory instance
 SessionFactory factory = configuration.buildSessionFactory(serviceRegistry);

 // Get current session
 Session session = factory.getCurrentSession();

 // Begin transaction
 session.getTransaction().begin();

 // Print out all required information
 System.out.println("Session Is Opened :: "+session.isOpen());
 System.out.println("Session Is Connected :: "+session.isConnected()); 

 // Commit transaction
 session.getTransaction().commit();

 System.exit(0);
 }
}

Hibernate Example Application Output