Requet域监听器

一、认识Requet域监听器

Requet域共有两个监听器接口,分别是

ServletRequestListener

ServleRequestAttributeListener

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

二、定义监听器类

package com.lanson.listener;import javax.servlet.*;/** * @Author: Lansonli * @Description: MircoMessage:Mark_7001 */public class MyRequestListener implements ServletRequestListener, ServletRequestAttributeListener {    @Override    public void requestDestroyed(ServletRequestEvent sre) {        // 监听HttpServletRequest对象的销毁  项目中任何一个Request对象的销毁都会触发该方法的执行        ServletRequest servletRequest = sre.getServletRequest();        System.out.println("request"+servletRequest.hashCode()+"对象销毁了");    }    @Override    public void requestInitialized(ServletRequestEvent sre) {        // 监听HttpServletRequest对象的创建并初始化 项目中任何一个Request对象的创建并初始化都会触发该方法的执行        ServletRequest servletRequest = sre.getServletRequest();        System.out.println("request"+servletRequest.hashCode()+"对象初始化");    }    @Override    public void attributeAdded(ServletRequestAttributeEvent srae) {        // 任何一个Request对象中调用 setAttribute方法增加了数据都会触发该方法        ServletRequest servletRequest = srae.getServletRequest();        String name = srae.getName();        Object value = srae.getValue();        System.out.println("request"+servletRequest.hashCode()+"对象增加了数据:"+name+"="+value);    }    @Override    public void attributeRemoved(ServletRequestAttributeEvent srae) {       // 任何一个Request对象中调用 removeAttribute方法移除了数据都会触发该方法        ServletRequest servletRequest = srae.getServletRequest();        String name = srae.getName();        Object value = srae.getValue();        System.out.println("request"+servletRequest.hashCode()+"对象删除了数据:"+name+"="+value);    }    @Override    public void attributeReplaced(ServletRequestAttributeEvent srae) {        // 任何一个Request对象中调用 setAttribute方法修改了数据都会触发该方法        ServletRequest servletRequest = srae.getServletRequest();        String name = srae.getName();        Object value = srae.getValue();        Object newValue=servletRequest.getAttribute(name);        System.out.println("request"+servletRequest.hashCode()+"对象增修改了数据:"+name+"="+value+"设置为:"+newValue);    }}

三、配置监听器

使用web.xml 或者通过@WebListener注解都可以

                com.lanson.listener.MyRequestListener

四、准备Servlet

@WebServlet(urlPatterns = "/myServlet3.do")public class MyServlet3 extends HttpServlet {    @Override    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        req.setAttribute("name", "zhangsan");        req.setAttribute("name", "lisi");        req.removeAttribute("name");    }}

X 关闭