一、实验内容
1、Filter的理解和应用
实现一个禁止缓存的过滤器。
要求和提示:
(1)禁止浏览器缓存所有动态页面;
(2)有3个http响应头字段可以禁止浏览器缓存当前页面,它们在Servlet中的示例代码如下。
response.setDateHeader("Expires",-1);
response.setHeader("Cache-Control","no-cache");
response.setHeader("Pragma","no-cache");
(3)并不是所有的浏览器都能完全支持上面的3个响应头,因此最好是同时使用上面的3个响应头。
2、Filter的理解和应用
设计一个简单的IP地址过滤器,根据用户的IP地址进行网站的访问控制。例如:禁止IP地址处在192.168.2网段的用户对网站的访问。
3、Listener的理解和应用
通过监听器记录在线用户的姓名,在页面进行用户姓名的显示,同时实现对某个用户的强制下线功能。
二、实验要求
源代码和测试截图(均直接输入到答题框中)
三、实验原理
过滤器原理
直白的说,就是这幅图
对应的是以下代码里面的三个方法
屏幕快照 2018-11-22 上午10.32.16.png
注意
web.xml格式
<filter> <filter-name>此处给过滤器起一个名字</filter-name> <filter-class>此处写过滤器实现类的全类名</filter-class> <init-param> <param-name>此处填写该过滤器初始化参数的名称</param-name> <param-value>此处填写该过滤器初始化参数的值</param-value> </init-param> </filter> <filter-mapping> <filter-name>此处用上边起过的名字</filter-name> <url-mapping>此处写我们需要过滤哪些URL请求</url-mapping> <dispacher>REQUEST,FORWORDMINCLUDE.ERROE</dispacher>
四、实验代码
实验1️⃣:
分为三个文件FirstFilter.java(用于执行过滤器的业务逻辑)、web.xml(用于配置过滤器的映射)、index.jsp(用作展示的页面)
//FirstFilter.javapackage topus;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.annotation.WebFilter;//import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet Filter implementation class FirstFilter */@WebFilter("/FirstFilter")public class FirstFilter implements Filter { /** * Default constructor. */ public FirstFilter() { // TODO Auto-generated constructor stub } /** * @see Filter#destroy() */ public void destroy() { System.out.println("First Filter------Destory"); } /** * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain) */ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { System.out.println("First Filter------doFilter start"); //HttpServletRequest req=(HttpServletRequest) request; HttpServletResponse res=(HttpServletResponse) response; res.setDateHeader("Expires",-1);// //指定网页在缓存中的过期时间 res.setHeader("Cache-Control","no-cache");// //HTTP消息头,控制网页的缓存 res.setHeader("Pragma","no-cache");// //禁止浏览器从缓存中调阅页面内容 // pass the request along the filter chain chain.doFilter(request, response); System.out.println("First Filter------doFilter end"); } /** * @see Filter#init(FilterConfig) */ public void init(FilterConfig fConfig) throws ServletException { System.out.println("First Filter------Init"); } }
//web.xml<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <display-name>shiyan10-1</display-name> <filter> <filter-name>firstFilter</filter-name> <filter-class>topus.FirstFilter</filter-class> </filter> <filter-mapping> <filter-name>firstFilter</filter-name> <!-- 代指所有url --> <url-pattern>/*</url-pattern> </filter-mapping></web-app>
//index.jsp<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body><h2>Hello World!</h2> <% System.out.println("index.jsp------"); %></body></html>
实验结果
no-cache
注意
在此,检测办法是在Chrome-右键-检查-network-选择对应文件-header,如果出现no-cache则证明过滤成功
实验2️⃣:
思路:访问index.jxp,触发过滤器,筛选IP,若不满足则跳转到error.jsp
index.jxp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body><h2>index!</h2> <% System.out.println("index.jsp------"); %></body></html>
error.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body><h2>error!</h2> <% System.out.println("error.jsp------"); %></body></html>
IPFilter.jsp
package topus;import java.io.IOException;//import java.net.InetAddress;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.annotation.WebFilter;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;//import org.apache.tomcat.util.codec.binary.StringUtils;/** * Servlet Filter implementation class IPFilter */@WebFilter("/IPFilter")public class IPFilter implements Filter { /** * Default constructor. */ public IPFilter() { // TODO Auto-generated constructor stub } /** * @see Filter#destroy() */ public void destroy() { // TODO Auto-generated method stub } /** * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain) */ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HttpServletRequest request1 = (HttpServletRequest)request; HttpServletResponse response1 = (HttpServletResponse)response; //四种痛苦的尝试 //1.这里tomcat只能获取IPV6的地址0:0:0:0:0:0:0:1不好判断 //String ip= request.getRemoteAddr(); //2.如此之判断还是得不到 /* String ip = request1.getHeader("x-forwarded-for"); if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ ip = request1.getHeader("Proxy-Client-IP"); } if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ ip = request1.getHeader("WL-Proxy-Client-IP"); } if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ ip = request1.getRemoteAddr(); } */ //3.这里用getLocalHost()模拟 //getLocalHost()仅返回象征本地主机的InetAddress对象 //InetAddress inet = InetAddress.getLocalHost(); //String ip= inet.getHostAddress(); //4.这里用字符模拟假的ip实例(前面实力劝退) String ip = "192.165.2.47" ; System.out.println("the ip is"+ip); //拆分字符 int ad = Integer.parseInt(ip.substring(ip.lastIndexOf(".") + 1)); if(ad >= 1 && ad <= 50){ response.setContentType("text/html;charset=utf-8"); //跳转到error.jsp request1.getRequestDispatcher("error.jsp").forward(request1, response1); } else{ chain.doFilter(request, response); } } /** * @see Filter#init(FilterConfig) */ public void init(FilterConfig fConfig) throws ServletException { // TODO Auto-generated method stub } }
IP不符合要求不允许访问
实验3️⃣:
实验三比较复杂,思路正确实现起来还是很简单的,项目结构:
作者:Topus
链接:https://www.jianshu.com/p/1cf4ab2f7e21
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