Hibernate4 下的hibernateUtil

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

public class HibernateUtil
{
    private static final SessionFactory sessionFactory;
    static
    {
        try
        {
            Configuration cfg = new Configuration().configure();
            ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(cfg.getProperties()).build();

            sessionFactory = cfg.buildSessionFactory(serviceRegistry);
        }
        catch (Throwable e)
        {
            throw new ExceptionInInitializerError(e);
        }
    }

    private HibernateUtil()
    {
    }

    public static SessionFactory getSessionFactory()
    {
        return sessionFactory;
    }

}