hibernate学习之三——hibernate核心API

//1，属性文件properties
Configuration config=new Configuration();
//2,xml文件
//解析配置文件
//2.1,默认解析hibernate.cfg.xml文件
Configuration conf = new Configuration().configure();
//2.2,指定解析文件
Configuration conf=new Configuration().configure("hibernate.cfg.xml");

Configuration conf=new Configuration().configure("hibernate.cfg.xml");
//根据解析对象获取sessionFactory
SessionFactory sessionFactory=conf.buildSessionFactory();
    /**
     *
说明：
1) SessionFactory 是线程安全的。
2) 构造 SessionFactory 很消耗资源，一般情况下一个应用中只初始化 一个SessionFactory 对象。
3) SessionFactory 是生成 Session 的工厂：
Session session = sessionFactory.openSession();
     */

package com.test;

import org.hibernate.Session;
import org.hibernate.SessionFactory;

import com.bean.User;
import com.util.HibernateUtil;

public class SessionApi {

private static SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

public static void save(){
//1,获取session对象
Session session = sessionFactory.openSession();
//2,开启事务
session.beginTransaction();

User user = new User();
user.setUid("5");
user.setName("xiaoming");
user.setAge(20);
//3,调用save方法
session.save(user);
//4，提交事务
session.getTransaction().commit();
//5，关闭资源
session.close();
}

public static void update(){
Session session = sessionFactory.openSession();
session.beginTransaction();
User user = new User();
user.setUid("5");
user.setName("xiaohong");

session.update(user);
session.getTransaction().commit();
session.close();
}

//存在就更新，不存在插入
public static void saveOrUpdate(){
Session session = sessionFactory.openSession();
session.beginTransaction();
User user = new User();
//	user.setUid(4);
//	Hibernate: select user_.Uid, user_.Name as Name0_, user_.Age as Age0_ from user user_ where user_.Uid=?
//			Hibernate: update user set Name=?, Age=? where Uid=?
user.setUid("6");
//	Hibernate: select user_.Uid, user_.Name as Name0_, user_.Age as Age0_ from user user_ where user_.Uid=?
//			Hibernate: insert into user (Name, Age, Uid) values (?, ?, ?)
user.setName("dada");
user.setAge(11);

session.saveOrUpdate(user);
session.getTransaction().commit();
session.close();
}

public static void query(){
//1,获取session对象
Session session = sessionFactory.openSession();
//2,调用load,get方法
//bean.class,主键id的值 String类型 bean类id也要String
//Object obj = session.load(User.class, "1");
Object obj = session.get(User.class, "1");

System.out.println("------使用obj的分割线-------");
System.out.println(obj);
//load方法使用时才加载 延迟加载
//------使用obj的分割线-------
//Hibernate: select user0_.Uid as Uid0_0_, user0_.Name as Name0_0_, user0_.Age as Age0_0_ from user user0_ where user0_.Uid=?
//User [uid=1, name=dongdong, age=20]

//get方法 即时加载
//Hibernate: select user0_.Uid as Uid0_0_, user0_.Name as Name0_0_, user0_.Age as Age0_0_ from user user0_ where user0_.Uid=?
//------使用obj的分割线-------
//User [uid=1, name=dongdong, age=20]

session.close();
}

public static void delete(){
Session session = sessionFactory.openSession();
session.beginTransaction();
User user = new User();
user.setUid("3");
session.delete(user);
session.getTransaction().commit();
session.close();

}
public static void main(String[] args) {

//save();
//update();
//saveOrUpdate();
//query();
delete();
}
}

public static void update() {
/*
获得事务对象： Transaction tx = session.beginTransaction();
常用方法:
1) commit():提交相关联的 session实例
2) rollback():撤销事务操作
3) wasCommitted():检查事务是否提交
*/
User user = new User();
user.setUid("5");
user.setName("xiaohong");
Session session = sessionFactory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
session.update(user);
tx.commit();
} catch (HibernateException ex) {
ex.printStackTrace();
tx.rollback();
} finally {
if (session != null) {
session.close();
}
}

}