Listener系列教材 （四）- Request

 

对Request的监听分生命周期的监听，和Request上Attribute变化的监听两部分。

步骤1:编写 RequestListener
步骤2:配置web.xml
步骤3:testRequest.jsp
步骤4:测试

步骤 1 : 编写 RequestListener

RequestListener 实现接口 ServletRequestListener和ServletRequestAttributeListener 
 

requestInitialized()

当新创建了一个Request的时候触发，只要访问了服务端的资源，就会创建一个Request，无论是jsp,servlet还是html

requestDestroyed()

当本次请求结束的时候触发

attributeAdded

当有新增属性时触发

attributeReplaced

当有替换属性时触发

attributeRemoved

当有移除属性时触发

package listener;

import javax.servlet.ServletRequestAttributeEvent;

import javax.servlet.ServletRequestAttributeListener;

import javax.servlet.ServletRequestEvent;

import javax.servlet.ServletRequestListener;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

public class RequestListener implements ServletRequestListener, ServletRequestAttributeListener {

    @Override

    public void requestDestroyed(ServletRequestEvent arg0) {

        System.out.println("销毁了一个Request ");

    }

    @Override

    public void requestInitialized(ServletRequestEvent arg0) {

        System.out.println("创建了一个Request ");

    }

    @Override

    public void attributeAdded(ServletRequestAttributeEvent e) {

        System.out.println("request 增加属性 ");

        System.out.println("属性是" + e.getName());

        System.out.println("值是" + e.getValue());

    }

    @Override

    public void attributeRemoved(ServletRequestAttributeEvent arg0) {

        System.out.println("request 移除属性 ");

         

    }

    @Override

    public void attributeReplaced(ServletRequestAttributeEvent arg0) {

        System.out.println("request 替换属性 ");

         

    }

}

步骤 2 : 配置web.xml

<listener>

    <listener-class>listener.RequestListener</listener-class>

</listener>   

步骤 3 : testRequest.jsp

测试页面，先在request中设置test,然后替换，最后移出掉test

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<%

    request.setAttribute("test", 1);

    request.setAttribute("test", 2);

    request.removeAttribute("test");

%>

步骤 4 : 测试

访问页面

http://127.0.0.1/testRequest.jsp

观察测试结果

更多内容，点击了解： https://how2j.cn/k/listener/listener-request/607.html