Web应用开发: JSP语法编程实践(六)：Filter和Listener编程实践
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
直白的说，就是这幅图
对应的是以下代码里面的三个方法
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.java
package 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>
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
}
}
###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：
login.jsp (登录界面)
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录界面</title>
</head>
<body>
<form name="logForm" action="loginPro.jsp" method="get">
<p>用户名：<input type="text" name="username"></p>
<p><input type="submit" value="登录"></p>
</form>
</body>
</html>
loginPro.jsp (用于对登录界面的值进行处理，以及触发监听器)
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录界面解析</title>
</head>
<body>
<%
String username = request.getParameter("username");
session.setAttribute("username",username);
//直接跳转
/* response.sendRedirect("users.jsp"); */
if(!username.isEmpty()){
out.println(username+"登陆成功");
}else out.println("登陆失败");
%>
<a href="users.jsp">跳转到用户中心</a>
</body>
</html>
logout.jsp(退出按钮所跳转的界面，用于对退出进行处理)
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="java.util.Map" import="topus.UserSessionInfo" import="topus.MySessionContext"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>用户退出</title>
</head>
<body>
<p>该用户已经退出本系统！</p>
<a href="users.jsp">跳转到用户中心</a>
<%
String sessionID = request.getParameter("sessionID");
//out.println(sessionID);
MySessionContext myc= MySessionContext.getInstance();
HttpSession sess = myc.getSession(sessionID);
//HttpSession sess = session.getSessionContext().getSession(sessionID) ;
sess.invalidate(); // 本次会话对象失效
//session.removeAttribute("username");
//response.sendRedirect("users.jsp");
//Map<String, UserSessionInfo> onlineRegister=(Map<String, UserSessionInfo>) application.getAttribute("onlineRegister");
//onlineRegister.remove(sess.getId());
//application.setAttribute("onlineRegister",onlineRegister);
//Map<String, UserSessionInfo> onlineRegister = (Map<String, UserSessionInfo>) session.getServletContext().getAttribute("onlineRegister");
//onlineRegister.remove(session.getId());
//session.getServletContext().setAttribute("onlineRegister",onlineRegister);
%>
</body>
</html>
users.jsp(用户管理中心，用于显示在线用户的信息，以及对在线用户进行强制下线操作)
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>用户管理中心</title>
</head>
<body>
<%-- ${applicationScope.onlineRegister} --%>
<c:forEach items="${applicationScope.onlineRegister}" var="mapRegister">
<p>
用户名：${mapRegister.value.username}，会话创建时间：
<fmt:formatDate value="${mapRegister.value.creationDate}"
pattern="yyyy-MM-dd HH:mm:ss" />
<%-- sessionID：${mapRegister.value.sessionID} --%>
<a href="logout.jsp?sessionID=${mapRegister.value.sessionID}">退出</a>
</p>
</c:forEach>
</body>
</html>
MySessionAttributeListener.java(SessionAttributeListener监听器，用于监听session的参数，如在logPro.jsp内的session.setAttribute有用到)
package topus;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
/**
* Application Lifecycle Listener implementation class MySessionAttributeListener
*
*/
@WebListener
public class MySessionAttributeListener implements HttpSessionAttributeListener {
/**
* Default constructor.
*/
public MySessionAttributeListener() {
// TODO Auto-generated constructor stub
}
/**
* @see HttpSessionAttributeListener#attributeAdded(HttpSessionBindingEvent)
*/
@SuppressWarnings("unchecked")
public void attributeAdded(HttpSessionBindingEvent arg0) {
HttpSession session = arg0.getSession();
String username = (String) session.getAttribute("username");
if (username != null) {
//给用户模型赋值
UserSessionInfo userSessionBean = new UserSessionInfo(username,session.getId(), new Date(session.getCreationTime()));
//建一个map表
Map<String, UserSessionInfo> onlineRegister = (Map<String, UserSessionInfo>) session.getServletContext().getAttribute("onlineRegister");
if (onlineRegister == null) {
onlineRegister = new HashMap<String, UserSessionInfo>();
}
//将sessionId和用户模型一一对应构成一个单独的个体
onlineRegister.put(session.getId(), userSessionBean);
//set回去
session.getServletContext().setAttribute("onlineRegister",onlineRegister);
}
}
/**
* @see HttpSessionAttributeListener#attributeRemoved(HttpSessionBindingEvent)
*/
@SuppressWarnings("unchecked")
public void attributeRemoved(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
if ("username".equals(arg0.getName())) {
HttpSession session = arg0.getSession();
Map<String, UserSessionInfo> onlineRegister = (Map<String, UserSessionInfo>) session
.getServletContext().getAttribute("onlineRegister");
onlineRegister.remove(session.getId());
session.getServletContext().setAttribute("onlineRegister",
onlineRegister);
}
}
/**
* @see HttpSessionAttributeListener#attributeReplaced(HttpSessionBindingEvent)
*/
public void attributeReplaced(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
}
}
MySessionContext.java和SessionListener.java 用于完成通过seesionID来获取到session的事件，魔改过来使用
作者csdn链接：http://www.javashuo.com/article/p-xplucsym-mo.html
package topus;
import java.util.HashMap;
import javax.servlet.http.HttpSession;
public class MySessionContext {
private static MySessionContext instance;
private HashMap<String,HttpSession> sessionMap;
private MySessionContext() {
sessionMap = new HashMap<String,HttpSession>();
}
public static MySessionContext getInstance() {
if (instance == null) {
instance = new MySessionContext();
}
return instance;
}
public synchronized void addSession(HttpSession session) {
if (session != null) {
sessionMap.put(session.getId(), session);
}
}
public synchronized void delSession(HttpSession session) {
if (session != null) {
sessionMap.remove(session.getId());
}
}
public synchronized HttpSession getSession(String sessionID) {
if (sessionID == null) {
return null;
}
return sessionMap.get(sessionID);
}
}
package topus;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
/**
* Application Lifecycle Listener implementation class SessionListener
*
*/
@WebListener
public class SessionListener implements HttpSessionListener {
private MySessionContext myc = MySessionContext.getInstance();
/**
* Default constructor.
*/
public SessionListener() {
// TODO Auto-generated constructor stub
}
/**
* @see HttpSessionListener#sessionCreated(HttpSessionEvent)
*/
public void sessionCreated(HttpSessionEvent se) {
// TODO Auto-generated method stub
HttpSession session = se.getSession();
myc.addSession(session);
}
/**
* @see HttpSessionListener#sessionDestroyed(HttpSessionEvent)
*/
public void sessionDestroyed(HttpSessionEvent se) {
// TODO Auto-generated method stub
HttpSession session = se.getSession();
myc.delSession(session);
}
}
UserSessionInfo.jsp(用于构建用户数据模型的Javabean)
package topus;
import java.util.Date;
public class UserSessionInfo {
private String username;
private String sessionID;
private Date creationDate;
public UserSessionInfo(){
}
public UserSessionInfo(String username, String sessionID, Date creationDate) {
super();
this.username = username;
this.sessionID = sessionID;
this.creationDate = creationDate;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getSessionID() {
return sessionID;
}
public void setSessionID(String sessionID) {
this.sessionID = sessionID;
}
public Date getCreationDate() {
return creationDate;
}
public void setCreationDate(Date creationDate) {
this.creationDate = creationDate;
}
}
项目截图：