clear(), evict(), flush()三种方法的用法实例

@Before
public void init() {
System.out.println("Test开始之前执行");
Configuration configuration = new Configuration().configure();
ServiceRegistry serviceRegistry =
new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
session = sessionFactory.openSession();
transaction = session.beginTransaction();
}

@Test
public void testClear() {
System.out.println("clear方法的实现");
News news2 = new News();
News news3 = new News();
News news4 = new News();
news2 = (News)session.get(News.class, 360448);
System.out.println(news2);
//        session.clear();//清除全部的缓存
session.evict(news2);
news3 = (News)session.get(News.class, 360448);
System.out.println(news3);
session.evict(news3);//evict方法是清除指定的缓存
news4 = (News)session.get(News.class, 360448);
System.out.println(news4);

//        News t = (News) session.get(News.class, 9);
//        System.out.println(t.getTitle());
//        session.clear();//这里不clear只会执行一次sql语句，有clear会执行2次
//        News t2 = (News) session.get(News.class, 9);
//        System.out.println(t2.getTitle());
}

@Test
public void testFlush() {
System.out.println("演示flush方法");
News t = (News) session.get(News.class, 9);
//提交事务
transaction.commit();
//关闭会话和会话工厂
session.close();
sessionFactory.close();
t.setTitle("标题第五次");
//session.flush();//有flush会执行2次UPDAE,没有会只执行一次
//t.setTitle("标题第三次");
init();
session.saveOrUpdate(t);    //使用saveOrUpdate方法重新转成持久化状态
transaction.commit();
//关闭会话和会话工厂
session.close();
sessionFactory.close();
}