hibernate的封装

1. 创建Configuration对象

2. 获取sessionfactory对象

3. 获取session

4. 开启事务transaction

public class HibernateUtil {
	 private static final SessionFactory FACTORY=buildSessionFactory();  //建一个session工厂
	 private static final ThreadLocal<Session> THREAD_LOCAL=new ThreadLocal<>();
 //保证线程安全，构建一个线程锁，保证该线程未结束前不会被占用

	 
		 /**
		  * 创建sessionfactory
		  * @return
		  */
		public  static SessionFactory buildSessionFactory() {
			// TODO Auto-generated method stub
			Configuration configuration  = new Configuration().configure();
			return configuration.buildSessionFactory();
		}
		
		/**
		 * 获取session，单例模式
		 */
		public static Session getSession(){
			Session session= THREAD_LOCAL.get();
			if (session==null) {//如果session是空的，打开一个session
				session=FACTORY.openSession();
			}
			THREAD_LOCAL.set(session);//保存session
			return session;
		}
		
		/**
		 * 关闭session
		 */
		public static void closeSession(){
		
			Session session= THREAD_LOCAL.get();
			if (session!=null) {
				session.close();
				THREAD_LOCAL.set(null);
			}
		
		}
}