JavaWeb_(Hibernate框架)Hibernate中对象的三种状态

package com.Gary.dao;


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

import com.Gary.domain.User;

public class UserDao {


    //增加用户
    public void addUser() {
        
        //得到配置信息
        Configuration config = new Configuration().configure();
        //创建sessionFactiory对象
        SessionFactory sessionFactory = config.buildSessionFactory();
        //获取session
        Session session = sessionFactory.openSession();
        //打开事务
        Transaction transcation = session.beginTransaction();
        
        //存储user对象save         只是为了生成id
        //有id，与session有关联，持久化状态
        User user = new User();        // =>没有id, 没有与session关联  瞬时状态
        user.setName("Gary");        //=>没有id, 没有与session关联  瞬时状态
        
        //存储user对象
        session.save(user);            //有id，与session关联  持久化状态    本质：对象状态的转换
                                    //将瞬时->持久    目的：生成id
                
        System.out.println(user.getId());
        
        System.out.println("////////////////////////////////////////");
        
        //提交事务
        transcation.commit();
        //关闭资源
        session.close();    //没有与session关联，有id

        
    }

    
    //删除用户
    public void deleteUser()
    {
        Configuration config = new Configuration().configure();
        SessionFactory factory = config.buildSessionFactory();
        Session session = factory.openSession();
        Transaction transcation = session.beginTransaction();
        //得到id为d03de4eb-e033-41c1-9da0-c9f155713e18的对象
        User user = session.get(User.class, "d03de4eb-e033-41c1-9da0-c9f155713e18");
        session.delete(user);
        transcation.commit();
        session.close();
    }
    
    
    //修改用户
    public void ChangeUser()
    {
        //读取hibernate.cfg.xml
        Configuration config = new Configuration().configure();
        //获取sessionFactory工厂
        SessionFactory factory = config.buildSessionFactory();
        //获取session
        Session session = factory.openSession();
        //开启事务
        Transaction transaction = session.beginTransaction();
        //根据id，得到session
        User user = session.get(User.class, "d03de4eb-e033-41c1-9da0-c9f155713e18");
        //修改名字,将对象改名为lGary
        user.setUsername("lGary");
        //更新数据库中的值
        session.update(user);
        //提交事务
        transaction.commit();
        //关闭session
        session.close();
    }
    
    
    //查询用户
    public void findUser()
    {
        Configuration config = new Configuration().configure();
        SessionFactory factory = config.buildSessionFactory();
        Session openSession = factory.openSession();
        Transaction transaction = openSession.beginTransaction();
        User user = openSession.get(User.class, "d03de4eb-e033-41c1-9da0-c9f155713e18");
        System.out.println(user);
        transaction.commit();
        openSession.close();
    }
    
}