servlet属性值的改变;

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1.新建一个Demo4代码如下:

package com.ask.listener;

import javax.servlet.ServletContextAttributeEvent;

import javax.servlet.ServletContextAttributeListener;

//servlet属性值的改变;

public class Demo4 implements ServletContextAttributeListener {

//增加

public void attributeAdded(ServletContextAttributeEvent scab) {

System.out.println("attributeAdded");

System.out.println(scab.getName()+" "+scab.getValue());

}

//移除

public void attributeRemoved(ServletContextAttributeEvent scab) {

System.out.println("attributeRemoved");

System.out.println(scab.getName()+ " "+scab.getValue());

}

//取代;

public void attributeReplaced(ServletContextAttributeEvent scab) {

System.out.println("attributeReplaced");

System.out.println(scab.getName()+" "+scab.getValue());

}

2.新建一个index.jsp增加代码如下:

<body>

application.setAttribute("name", "tom");

application.setAttribute("sal", "6000");

application.removeAttribute("sal");

</body>

3.web.xml配置文件代码如下:

<listener-class>com.ask.listener.Demo4</listener-class>

</listener>

4．程序运行如下：

attributeReplaced

name tom

attributeAdded

sal 6000

attributeRemoved

sal 6000

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