Java examples on org.hibernate

How do I create Hibernate's SessionFactory?

When creating an application the use Hibernate to manage our application persistence object we'll need a SessionFactory. This factory creates or open a session to talk to a database.

To create a SessionFactory we can define the configuration in hibernate.properties, hibernate.cfg.xml or create it programatically. In this example we'll use the hibernate.cfg.xml configuration file, which is mostly use when creating Hibernate application.

Below is our session configuration files.

<?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>
        <!-- JDBC connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost/exampledb</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>
        
        <!-- JDBC connection pool, use Hibernate internal connection pool -->
        <property name="connection.pool_size">5</property>

        <!-- Defines the SQL dialect used in Hibernate application -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>

        <!-- Enable Hibernate 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>

        <!-- Display and format all executed SQL to stdout -->
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>
        
        <!-- Mapping to hibernate mapping files -->
        <!--mapping resource="org/kodejava/example/hibernate/model/Label.hbm.xml"/-->
    </session-factory>
</hibernate-configuration>

Now we have the configuration file done, let's create a helper class that will configure and build the SessionFactory object. This helper will be used in other Hibernate example in this site.

package org.kodejava.example.hibernate.app;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class SessionFactoryHelper {
    private static final SessionFactory sessionFactory;

    static {
        try {
            //
            // Build a SessionFactory object from session-factory configuration
            // defined in the hibernate.cfg.xml file. In this file we register
            // the JDBC connection information, connection pool, the hibernate
            // dialect that we used and the mapping to our hbm.xml file for each
            // Pojo (Plain Old Java Object).
            //
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable e) {
            System.err.println("Error in creating SessionFactory object."
                    + e.getMessage());
            throw new ExceptionInInitializerError(e);
        }
    }

    /**
     * A static method for other application to get SessionFactory object
     * initialized in this helper class.
     */
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}