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