Servlet监听器在开发中的应用案例
案例：显示登陆用户列表，并实现踢人功能。 登陆的jsp页面------------------------
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><title>My JSP 'login.jsp' starting page</title></head><body><form action="${pageContext.request.contextPath}/LoginServlet" method="post">用户名：<input type="text" name="username"><br>密 码：<input type="text" name="password"><br><input type="submit" value="登陆"></form></body></html>package com.hbsi.servlet;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.hbsi.domain.User;public class LoginServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String username=request.getParameter("username");String password=request.getParameter("password");User user=new User();user.setUsername(username);user.setPassword(password);request.getSession().setAttribute("user",user);response.sendRedirect("/ListenerKicking/index.jsp");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>My JSP 'index.jsp' starting page</title> </head> <body> 欢迎您：${user.username} <br> </body></html><%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><title>My JSP 'userJsp.jsp' starting page</title></head><body>当前在线用户为：<br /><c:forEach items="${map}" var="me"><c:url value="/KickUserServlet" var="url"><c:param name="username" value="${me.key}"></c:param></c:url> ${me.key}<a href="${url}">剔出去</a><br /></c:forEach></body></html>package com.hbsi.servlet;import java.io.IOException;import java.util.Map;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class KickUserServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String username=request.getParameter("username");username=new String(username.getBytes("iso8859-1"),"Utf-8");Map map=(Map) this.getServletContext().getAttribute("map");HttpSession session=(HttpSession) map.get(username);if(session!=null){session.invalidate();map.remove(username);}request.getRequestDispatcher("/userJsp.jsp").forward(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}
servlet监听器-------------
package com.hbsi.listener;import java.util.HashMap;import java.util.Map;import javax.servlet.http.HttpSession;import javax.servlet.http.HttpSessionAttributeListener;import javax.servlet.http.HttpSessionBindingEvent;import com.hbsi.domain.User;public class SessionListener implements HttpSessionAttributeListener {@Overridepublic void attributeAdded(HttpSessionBindingEvent se) {Object obj=se.getValue();if(obj instanceof User){User user=(User) obj; HttpSession session=se.getSession(); Map map=(Map) session.getServletContext().getAttribute("map"); if(map==null){ map=new HashMap(); session.getServletContext().setAttribute("map",map); } map.put(user.getUsername(),session);}}@Overridepublic void attributeRemoved(HttpSessionBindingEvent se) {}@Overridepublic void attributeReplaced(HttpSessionBindingEvent se) {// TODO Auto-generated method stub}}package com.hbsi.domain;public class User { private String username; private String password;public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;} }package com.hbsi.filter;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;public class CharseterEncodingFilter implements Filter {private FilterConfig config = null;private String defaultCharset = "UTF-8";@Overridepublic void destroy() {// TODO Auto-generated method stub}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {String charset = config.getInitParameter("charset");if(charset==null){charset = defaultCharset;}request.setCharacterEncoding(charset);response.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset="+charset);chain.doFilter(request, response);}@Overridepublic void init(FilterConfig filterConfig) throws ServletException {this.config = filterConfig;}}<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <filter> <filter-name>CharseterEncodingFilter</filter-name> <filter-class>com.hbsi.filter.CharseterEncodingFilter</filter-class> <init-param> <param-name>charset</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>CharseterEncodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <listener> <listener-class>com.hbsi.listener.SessionListener</listener-class> </listener> <servlet> <servlet-name>LoginServlet</servlet-name> <servlet-class>com.hbsi.servlet.LoginServlet</servlet-class> </servlet> <servlet> <servlet-name>KickUserServlet</servlet-name> <servlet-class>com.hbsi.servlet.KickUserServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/LoginServlet</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>KickUserServlet</servlet-name> <url-pattern>/KickUserServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list></web-app>
