HibernateUtils

由于SessionFactory是线程安全的，在hibernate中对应数据库，而且SessionFactory的创建过程是重量级的，创建比较耗时，通常只创建一次。所以用HibernateUtils类封装了SessionFactory：

package com.wyx.hibernate;

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

public class HibernateUtils {
	private static SessionFactory factory =null;
	
	static{
		try {
			//new Configuration()默认获取的是Hibernate.property
			factory = new Configuration().configure().buildSessionFactory();
		} catch (HibernateException e) {
			e.printStackTrace();
		}
	}
	public static Session getSession(){
		
		Session session = factory.openSession();
		return session;
	}
	public static void closeSession(Session session){
		if(session != null){
			if(session.isOpen()){
				session.close();
			}
		}	
	}
	public static SessionFactory getSessionFactory(){
		return factory;
	}
}