步骤 2 : 配置web.xml 步骤 3 : testRequest.jsp 步骤 4 : 测试
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 ");
}
}
<listener>
<listener-class>listener.RequestListener</listener-class>
</listener>
<listener> <listener-class>listener.RequestListener</listener-class> </listener>
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");
%>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <% request.setAttribute("test", 1); request.setAttribute("test", 2); request.removeAttribute("test"); %>
访问页面
http://127.0.0.1/testRequest.jsp 观察测试结果
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