JavaWeb---線上使用者顯示與管理---(監聽器/過濾器)
阿新 • • 發佈：2018-11-29
管理登入(線上使用者)：
第一步：書寫一個HttpSession的監聽，並維護一個LinkedHashMap，其中儲存著所有使用者的Session.
第二步：讓上面的類，同時實現ServletContextListener介面，並將LinkedHashMap新增到ServletContext對像中。
第三步：實現一個頁面，顯示所有SessionID。
第四步：在頁面上新增踢出按扭，通過SessionID在Map中查詢指定的Session，然後執行它的invalidate方法，清除它。從而實現踢出使用者的功能。
第五步：改進，應該通過HttpSessionAttributeListener監聽器，只踢出登入成功的使用者。對於遊客不用關心，並且只有管理員有許可權踢人。
index.jsp
<%@ 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>線上人資訊管理</title> </head> <body> <h2>線上人資訊管理</h2> <c:if test="${empty sessionScope.user}" var="boo"> <h3>會員登入</h3> <form action="<c:url value='/LoginServlet'/>" method="post"> 姓名:<input type="text" name="name" /><br/> <input type="submit" value="輸入任意名即可登入"/> </form> </c:if> <c:if test="${!boo}"> 歡迎你:${user.name } <c:if test="${user.admin}" var="bo"> 管理員 </c:if> <c:if test="${!bo}"> 會員 </c:if> <br/> <a href="<c:url value='/servlet/ShowServlet'/>">顯示所有線上使用者</a> <br/> <a href="<c:url value='/servlet/LogOutServlet'/>">安全退出</a> </c:if> </body> </html>
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name></display-name> <filter> <filter-name>charset</filter-name> <filter-class>cn.hncu.filter.CharsetFilter</filter-class> </filter> <filter> <filter-name>login</filter-name> <filter-class>cn.hncu.filter.LoginFilter</filter-class> </filter> <filter-mapping> <filter-name>charset</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <filter-mapping> <filter-name>login</filter-name> <url-pattern>/servlet/*</url-pattern> <url-pattern>/jsps/*</url-pattern> </filter-mapping> <listener> <listener-class>cn.hncu.listener.MySessionListener</listener-class> </listener> <servlet> <servlet-name>LoginServlet</servlet-name> <servlet-class>cn.hncu.servlet.LoginServlet</servlet-class> </servlet>
show.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>線上人資訊管理</title>
<style type="text/css">
table{
border: 1px solid red;
border-collapse: collapse;
width: 80%;
}
td{
border: 1px solid red;
padding:3px;
}
.header{
background: gray;
}
</style>
</head>
<body>
<h2>以下是所有線上使用者資訊</h2>
<table>
<tr class="header" >
<td>姓名</td> <td>上線時間</td> <td>最後訪問時間</td> <td>IP</td> <td>操作</td>
</tr>
<c:forEach items="${requestScope.onLines}" var="m" >
<tr>
<td>
<c:if test="${empty m.user}" var="boo">
遊客
</c:if>
<c:if test="${ !boo }">
${ m.user.name }
</c:if>
</td>
<td> ${m.creationTime} </td>
<td> ${m.lastAccessTime }</td>
<td> ${m.ip } </td>
<td>
<c:if test="${!boo && m.user.admin }">
<a href="<c:url value='/servlet/KickOutServlet?id=${m.id}'/> " >踢出</a>
</c:if>
</td>
</tr>
</c:forEach>
</table>
</body>
</html>過濾器：
CharsetFilter.java
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 CharsetFilter implements Filter{
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
//獲取該使用者的ip,儲存到它的session物件中
HttpServletRequest req = (HttpServletRequest) request;
if(req.getSession().getAttribute("ip")==null){
req.getSession().setAttribute("ip", req.getRemoteAddr() );
}
chain.doFilter(request, response);//放行
}
@Override
public void destroy() {
}
}LoginFilter.java
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 resp = (HttpServletResponse) response;
resp.sendRedirect(req.getContextPath()+"/index.jsp");
}else{
chain.doFilter(request, response);
}
}
@Override
public void destroy() {
}
}監聽器：
MySessionListener.java
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){//沙發
onLines = Collections.synchronizedMap( new HashMap<String, HttpSession>() ); //使用同步技術的Map
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() );
}
}
}值物件：
User.java
package cn.hncu.domain;
public class User {
private String name;
private String pwd;
private boolean admin;
public User() {
super();
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
public boolean isAdmin() {
return admin;
}
public void setAdmin(boolean admin) {
this.admin = admin;
}
}Servlet：
LoginServlet.java
package cn.hncu.servlet;
import java.io.IOException;
import java.util.Random;
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 = new User();
user.setName(name);
//用user作為引數到後臺登入，這裡我們簡化了，直接假設登入成功
Random r = new Random();
int a = r.nextInt(10);
if(a%2==0){
user.setAdmin(true);
}else{
user.setAdmin(false);
}
request.getSession().setAttribute("user", user);
response.sendRedirect(request.getContextPath()+"/index.jsp");
}
}ShowServlet.java
package cn.hncu.servlet;
import java.io.IOException;
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 java.util.Map.Entry;
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>) getServletContext().getAttribute("onLines");
List<Map<String,Object>> list = new ArrayList<Map<String,Object>>();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
//遍歷onlines，針對每個session物件封裝一個map(資訊包含:name,createTime,lastAccessTime,ip)，把該map新增到list當中
Iterator<Entry<String, HttpSession>> it = onLines.entrySet().iterator();
while(it.hasNext()){
Entry<String, HttpSession> en = it.next();
Map<String,Object> m = new HashMap<String, Object>();
m.put("id", en.getValue().getId());
m.put("user", en.getValue().getAttribute("user"));
String creationTime = sdf.format( new Date(en.getValue().getCreationTime()) );
m.put("creationTime", creationTime);
String lastAccessTime = sdf.format( new Date(en.getValue().getLastAccessedTime()) );
m.put("lastAccessTime", lastAccessTime);
m.put("ip", en.getValue().getAttribute("ip") ); //注意,該ip資料是在CharsetFilter中封裝的
list.add(m);
}
request.setAttribute("onLines",list);
request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
}
}LogOutServlet.java
package cn.hncu.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LogOutServlet 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");
}
}KickOutServlet.java
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 {
PrintWriter out = response.getWriter();
String id = request.getParameter("id");
Map<String, HttpSession> onLines = (Map<String, HttpSession>) getServletContext().getAttribute("onLines");
if(onLines.containsKey(id)){
HttpSession session = onLines.get(id);
session.invalidate();
out.println("該使用者已被踢出!");
}else{
out.println("該使用者已經不存在!");
}
}
}使用者登入介面如下：
登陸成功介面：
顯示聯絡人介面：
