Hibernate的二级缓存
HibernateTest.java
代码：
/** * */ package com.b510.examplex;
import org.hibernate.Session;
/** * * @author XHW * * @date 2011-7-15 * */ public class HibernateTest {
/** * @param args */ public static void main(String[] args) { new HibernateTest().getGuestbooks(); }
public void getGuestbooks(){ Session session=HibernateSessionFactoryUtil.getSessionFactory().openSession(); session.beginTransaction(); Guestbook gb=(Guestbook)session.get(Guestbook.class, 2); //移除gb的缓存 session.evict(gb); Guestbook gb2=(Guestbook)session.get(Guestbook.class, 2); System.out.println(gb==gb2); session.getTransaction().commit();
}
}
运行效果：
首先查出gb对象的数据，放入缓存中，当执行session.evict(gb);语句时，就会把
缓存中的数据移除掉。
这次要查gb2对象的数据，就得从新生成一条select语句。
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment). log4j:WARN Please initialize the log4j system properly. Hibernate: select guestbook0_.id as id0_0_, guestbook0_.version as version0_0_, guestbook0_.name as name0_0_, guestbook0_.email as email0_0_, guestbook0_.phone as phone0_0_, guestbook0_.title as title0_0_, guestbook0_.content as content0_0_, guestbook0_.created_time as created8_0_0_ from users.guestbook guestbook0_ where guestbook0_.id=? Hibernate: select guestbook0_.id as id0_0_, guestbook0_.version as version0_0_, guestbook0_.name as name0_0_, guestbook0_.email as email0_0_, guestbook0_.phone as phone0_0_, guestbook0_.title as title0_0_, guestbook0_.content as content0_0_, guestbook0_.created_time as created8_0_0_ from users.guestbook guestbook0_ where guestbook0_.id=? false
测试二：
HIbernateTest.java
代码：
/** * */ package com.b510.examplex;
import org.hibernate.Session;
/** * * @author XHW * * @date 2011-7-15 * */ public class HibernateTest {
/** * @param args */ public static void main(String[] args) { new HibernateTest().getGuestbooks(); }
public void getGuestbooks(){ Session session=HibernateSessionFactoryUtil.getSessionFactory().openSession(); session.beginTransaction(); Guestbook gb=(Guestbook)session.get(Guestbook.class, 2); Guestbook gb2=(Guestbook)session.get(Guestbook.class, 3); //清楚缓存，把缓存中的所有东西都给干掉，不留下任何东西 session.clear(); Guestbook gb3=(Guestbook)session.get(Guestbook.class, 2); Guestbook gb4=(Guestbook)session.get(Guestbook.class, 3); System.out.println(gb==gb3); System.out.println(gb2==gb4); session.getTransaction().commit();
}
}
运行效果：
我们看到session.clear();的执行效果果然是“心狠手辣”，不让敌人有丝毫反抗的有生力量……
这个方法会让缓存中的所有东西清除的干干净净。通通的，大大的，全部干掉的……
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment). log4j:WARN Please initialize the log4j system properly. Hibernate: select guestbook0_.id as id0_0_, guestbook0_.version as version0_0_, guestbook0_.name as name0_0_, guestbook0_.email as email0_0_, guestbook0_.phone as phone0_0_, guestbook0_.title as title0_0_, guestbook0_.content as content0_0_, guestbook0_.created_time as created8_0_0_ from users.guestbook guestbook0_ where guestbook0_.id=? Hibernate: select guestbook0_.id as id0_0_, guestbook0_.version as version0_0_, guestbook0_.name as name0_0_, guestbook0_.email as email0_0_, guestbook0_.phone as phone0_0_, guestbook0_.title as title0_0_, guestbook0_.content as content0_0_, guestbook0_.created_time as created8_0_0_ from users.guestbook guestbook0_ where guestbook0_.id=? Hibernate: select guestbook0_.id as id0_0_, guestbook0_.version as version0_0_, guestbook0_.name as name0_0_, guestbook0_.email as email0_0_, guestbook0_.phone as phone0_0_, guestbook0_.title as title0_0_, guestbook0_.content as content0_0_, guestbook0_.created_time as created8_0_0_ from users.guestbook guestbook0_ where guestbook0_.id=? Hibernate: select guestbook0_.id as id0_0_, guestbook0_.version as version0_0_, guestbook0_.name as name0_0_, guestbook0_.email as email0_0_, guestbook0_.phone as phone0_0_, guestbook0_.title as title0_0_, guestbook0_.content as content0_0_, guestbook0_.created_time as created8_0_0_ from users.guestbook guestbook0_ where guestbook0_.id=? false false
测试三：
HibernateTest.java
代码：
/** * */ package com.b510.examplex;
import org.hibernate.Session;
/** * * @author XHW * * @date 2011-7-15 * */ public class HibernateTest {
/** * @param args */ public static void main(String[] args) { new HibernateTest().test(); }
public void test(){ Session session=HibernateSessionFactoryUtil.getSessionFactory().openSession(); session.beginTransaction(); Guestbook gb=(Guestbook)session.get(Guestbook.class, 2); Guestbook gb2=(Guestbook)session.get(Guestbook.class, 3); //移除干净缓存中的数据 session.clear(); //判断gb2对象的是否在缓存中 System.out.println(session.contains(gb2));
//session.flush(); session刷新
//session.close(); session关闭
说明一下，在session执行下面的commit()方法后，会自动调用
flush()方法和close()方法。这两步是隐含在里面，所以不用显示出来
都是可以的。 session.getTransaction().commit();
}
}
运行效果：
session.contains(gb2);返回的是一个boolean值，判断缓存中是否缓存在gb2对象。
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment). log4j:WARN Please initialize the log4j system properly. Hibernate: select guestbook0_.id as id0_0_, guestbook0_.version as version0_0_, guestbook0_.name as name0_0_, guestbook0_.email as email0_0_, guestbook0_.phone as phone0_0_, guestbook0_.title as title0_0_, guestbook0_.content as content0_0_, guestbook0_.created_time as created8_0_0_ from users.guestbook guestbook0_ where guestbook0_.id=? Hibernate: select guestbook0_.id as id0_0_, guestbook0_.version as version0_0_, guestbook0_.name as name0_0_, guestbook0_.email as email0_0_, guestbook0_.phone as phone0_0_, guestbook0_.title as title0_0_, guestbook0_.content as content0_0_, guestbook0_.created_time as created8_0_0_ from users.guestbook guestbook0_ where guestbook0_.id=? false