Hibernate Helper Class

[Ryan Waggoner]

I am having trouble figuring out what this class is actually doing. I am using it and it is working fine, just not sure what is working fine...

Anyone have an explanation for me?

   
package util;
 
import org.hibernate.*;
import org.hibernate.cfg.*;
 
public class HibernateUtil {
 
    private static final SessionFactory sessionFactory;
 
    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
 
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
 
}
 

[Mark Spritzler]

Basically, what you have is a Singleton. See creating a SessionFactory is a big deal, it has so much work to do. It is considered a heavyweight object. So you want to make sure that you only create this once, hence the Singleton.

So anytime you app needs to get a Session, it can call the helper class Singleton get the instance of SessionFactory and call openSession() on it. Session objects are very lightweight. Almost empty when you call that method, there is a JDBC Connection set in the new Session, but it will get the Connection from the COnnection pool.

Mark

[Ryan Waggoner]

Great thanks, I didn't realize that the session factory was going to be such a heavyweight object.

Thanks.