11_Session域监听器

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 Session域共有四个监听器接口,分别是

HttpSessionListener
HttpSessionAttributeListener
HttpSessionBindingListener
HttpSessionActivationListener

接下来我们就认识一些每个接口和接口中每个方法的用处

监听器代码

HttpSessionListener
HttpSessionAttributeListener

package com.msb.listener;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
/**
 * @Author: Ma HaiYang
 * @Description: MircoMessage:Mark_7001
 */
@WebListener
public class MySessionListener implements HttpSessionListener , HttpSessionAttributeListener {
    @Override
    public void sessionCreated(HttpSessionEvent se) {
        System.out.println("任何一个Session对象创建");
    }
    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        System.out.println("任何一个Session对象的销毁");
    }
    @Override
    public void attributeAdded(HttpSessionBindingEvent se) {
        System.out.println("任何一个Session对象中添加了数据");
    }
    @Override
    public void attributeRemoved(HttpSessionBindingEvent se) {
        System.out.println("任何一个Session对象中移除了数据");
    }
    @Override
    public void attributeReplaced(HttpSessionBindingEvent se) {
        System.out.println("任何一个Session对象中修改了数据");
    }
}

HttpSessionBindingListener

package com.msb.listener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;
/**
 * @Author: Ma HaiYang
 * @Description: MircoMessage:Mark_7001
 */
/*
* 可以监听具体的某个session对象的事件的
*
* HttpSessionListener 只要在web.xml中配置或者通过@WebListener注解就可以注册监听所有的Session对象
* HttpSessionBindingListener 必须要通过setAttribute方法和某个session对象绑定之后,监听单独的某个Session对象
* */
public class MySessionBindingListener implements HttpSessionBindingListener {
    // 绑定方法
    /*
    session.setAttribute("mySessionBindingListener",new MySessionBindingListener())
     */
    @Override
    public void valueBound(HttpSessionBindingEvent event) {
        System.out.println("监听器和某个session对象绑定了");
    }
    // 解除绑定方法
    /*
    * 当发生如下情况,会触发该方法的运行
    * 1 session.invalidate(); 让session不可用
    * 2 session到达最大不活动时间,session对象回收 ;
    * 3 session.removeAttribute("mySessionBindingListener");手动解除绑定
    * */
    @Override
    public void valueUnbound(HttpSessionBindingEvent event) {
    }
}

HttpSessionActivationListener
 

package com.msb.listener;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionActivationListener;
import javax.servlet.http.HttpSessionEvent;
/**
 * @Author: Ma HaiYang
 * @Description: MircoMessage:Mark_7001
 */

public class MySessionActivationListener implements HttpSessionActivationListener {
    @Override
    public void sessionWillPassivate(HttpSessionEvent se) {
        System.out.println("session即将钝化");
    }
    @Override
    public void sessionDidActivate(HttpSessionEvent se) {
        System.out.println("session活化完毕");
    }
}