这篇博客是filter、listener和servlet技术的相关总结，实现了简单的显示在线人数、在线人详细信息、管理员踢人功能
下面是详细代码
web.xml
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<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<display-name></display-name>
<filter>
<filter-name>character</filter-name>
<filter-class>cn.hncu.filter.CharacterFilter</filter-class>
<init-param>
<param-name>charset</param-name>
<param-value>utf-8</param-value>
</init-param>
</filter>
<filter>
<filter-name>login</filter-name>
<filter-class>cn.hncu.filter.LoginFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>character</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>login</filter-name>
<url-pattern>/servlet/*</url-pattern>
<url-pattern>/jsps/*</url-pattern>
<dispatcher>REQUEST</dispatcher>
<dispatcher>FORWARD</dispatcher>
</filter-mapping>
<listener>
<listener-class>cn.hncu.listener.MySessionListener</listener-class>
</listener>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>cn.hncu.servlet.LoginServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>ShowServlet</servlet-name>
<servlet-class>cn.hncu.servlet.ShowServlet</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>KickOutServlet</servlet-name>
<servlet-class>cn.hncu.servlet.KickOutServlet</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>LoginOutServlet</servlet-name>
<servlet-class>cn.hncu.servlet.LoginOutServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ShowServlet</servlet-name>
<url-pattern>/servlet/ShowServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>KickOutServlet</servlet-name>
<url-pattern>/servlet/KickOutServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>LoginOutServlet</servlet-name>
<url-pattern>/servlet/LoginOutServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
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index.jsp
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<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>在线人信息管理</title>
</head>
<body>
<h2>在线人信息管理</h2>
<h3>会员登录</h3>
<c:if test="${ empty sessionScope.user.name}" var="boo">
<form action='<c:url value="/LoginServlet"></c:url>'>
姓名:<input type="text" name="name"><br/>
<input type="submit" value="登录"><br/>
</form>
</c:if>
<c:if test="${!boo}" >
欢迎回来,${ sessionScope.user.name}
<c:if test="${ sessionScope.user.admin}" var="bo">
管理员
</c:if>
<c:if test="${!bo}" >
会员
</c:if>
</c:if>
<br/>
<c:if test="${!boo}" var="boo">
<a href='<c:url value="/servlet/ShowServlet"/>'>查看在线人信息</a><br/>
<a href='<c:url value="/servlet/LoginOutServlet"/>'>安全退出</a><br/>
</c:if>
</body>
</html>
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/jsps/show.jsp
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<%@ 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>在线人信息</title>
<style type="text/css">
table {
color: green;
border: 1px solid blue;
border-collapse: collapse;
width: 500px;
margin: auto;
}
td {
border: 1px solid blue;
}
th {
border: 1px solid blue;
}
body {
text-align: center;
}
</style>
<meta http-equiv="refresh" content="3">
</head>
<body>
<table>
<tr>
<th>姓名</th>
<th>上线时间</th>
<th>最后访问时间</th>
<th>ip</th>
<th>操作</th>
</tr>
<c:forEach items="${requestScope.onlines}" var="online">
<tr>
<td>
<c:if test="${!empty online.user }" var="boo">
${online.user.name }
</c:if>
<c:if test="${empty online.user }">
游客
</c:if>
</td>
<td>${online.createTime }</td>
<td>${online.lastAccessedTime }</td>
<td>${online.ip }</td>
<td>
<c:if test="${online.user!=sessionScope.user }">
<c:if test="${!online.user.admin&&boo}">
<a href='<c:url value="/servlet/KickOutServlet?id=${online.id }"/>' >踢出</a>
</c:if>
</c:if>
</td>
</tr>
</c:forEach>
</table>
</body>
</html>
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User.java(值对象）
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package cn.hncu.domain;
public class User {
private String name;
private boolean admin;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public boolean isAdmin() {
return admin;
}
public void setAdmin(boolean admin) {
this.admin = admin;
}
@Override
public String toString() {
return "User [name=" + name + ", admin=" + admin + "]";
}
}
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MySessionListener.java(监听器）
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package cn.hncu.listener;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class MySessionListener implements HttpSessionListener{
@Override
public void sessionCreated(HttpSessionEvent se) {
Map<String, HttpSession> onlines= (Map<String, HttpSession>) se.getSession().getServletContext().getAttribute("onlines");
if(onlines==null){
onlines=Collections.synchronizedMap(new HashMap<String, HttpSession>());//对map进行加上同步锁
se.getSession().getServletContext().setAttribute("onlines",onlines);
}
onlines.put(se.getSession().getId(), se.getSession());
}
@Override
public void sessionDestroyed(HttpSessionEvent se) {
Map<String, HttpSession> onlines= (Map<String, HttpSession>) se.getSession().getServletContext().getAttribute("onlines");
if(onlines.containsKey(se.getSession().getId())){
onlines.remove(se.getSession().getId());
}
}
}
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CharacterFilter.java(字符过滤器）
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package cn.hncu.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;
import javax.servlet.http.HttpServletRequest;
public class CharacterFilter implements Filter {
private String charset;
@Override
public void init(FilterConfig filterConfig) throws ServletException {
charset=filterConfig.getInitParameter("charset");
}
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
request.setCharacterEncoding(charset);
response.setCharacterEncoding(charset);
HttpServletRequest req=(HttpServletRequest) request;
if(req.getSession().getAttribute("ip")==null){
req.getSession().setAttribute("ip", req.getRemoteAddr());
}
chain.doFilter(request, response);
}
@Override
public void destroy() {
}
}
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LoginFilter.java(防止游客乱访问过滤器）
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package cn.hncu.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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req=(HttpServletRequest) request;
if(req.getSession().getAttribute("user")==null){
((HttpServletResponse)response).sendRedirect(req.getContextPath()+"/index.jsp");
return;
}
chain.doFilter(request, response);
}
@Override
public void destroy() {
}
}
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LoginServlet.java
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package cn.hncu.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import cn.hncu.domain.User;
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String name=request.getParameter("name");
User user=(User) request.getSession().getAttribute("user");
if (user==null&&name!=null&&name.trim().length()>0) {//封装User
user = new User();
user.setName(name);
if(name.equals("admin")){
user.setAdmin(true);
}
}
request.getSession().setAttribute("user", user);
response.sendRedirect(request.getContextPath()+"/index.jsp");
}
}
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ShowServlet.java
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package cn.hncu.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
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 ShowServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Map<String, HttpSession> onlines=(Map<String, HttpSession>) request.getServletContext().getAttribute("onlines");
List<Map<String, Object>> list=new ArrayList<Map<String,Object>>();//吧Online封装成list
if (onlines!=null) {
Iterator<HttpSession> it = onlines.values().iterator();
while (it.hasNext()) {
HttpSession s = it.next();
Map<String, Object> map = new HashMap<String, Object>();
map.put("id", s.getId());
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
map.put("createTime", sdf.format(new Date(s.getCreationTime())));
map.put("lastAccessedTime",sdf.format(new Date(s.getLastAccessedTime())) );
map.put("ip", s.getAttribute("ip"));//ip信息在characterFilter中补
map.put("user", s.getAttribute("user"));
list.add(map);
}
}
request.setAttribute("onlines", list);
request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
}
}
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KickOutServlet.java
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package cn.hncu.servlet;
import java.io.IOException;
import java.io.PrintWriter;
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 KickOutServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String id=request.getParameter("id");
Map<String, HttpSession> onlines=(Map<String, HttpSession>) request.getServletContext().getAttribute("onlines");
if (onlines!=null) {
if (onlines.containsKey(id)) {
onlines.get(id).invalidate();
}
}
request.getRequestDispatcher("/servlet/ShowServlet").forward(request, response);
}
}
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LoginOutServlet.java
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package cn.hncu.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginOutServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.getSession().invalidate();
response.sendRedirect(request.getContextPath()+"/index.jsp");
}
}
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以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。