hibernate中执行hql语句创建session需要的HibernateUtil类

import org.hibernate.HibernateException;  
import org.hibernate.Session;  
import org.hibernate.SessionFactory;  
import org.hibernate.cfg.Configuration;  
  
public class HibernateUtil {  
  
    private static SessionFactory sessionFactory = null;  
  
    static {  
        try {  
            Configuration cfg = new Configuration().configure();  
            sessionFactory = cfg.buildSessionFactory();  
        } catch (HibernateException e) {  
            // TODO: handle exception  
            e.printStackTrace();  
        }  
    }  
  
    public static SessionFactory getSessionFactory() {  
        return sessionFactory;  
    }  
  
    public static Session getSession() {  
        Session session = (sessionFactory != null) ? sessionFactory.openSession() : null;  
        return session;  
    }  
  
    public static void closeFactory(Session session) {  
        if (session != null) {  
            if (session.isOpen()) {  
                session.close();  
            }  
        }  
    }  
}  

package org.hibernate.tutorial.util;  
  
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) {  
            // 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;  
    }  
  
}