实现在线人员的查询

来源：互联网发布：经传软件好用吗编辑：程序博客网时间：2024/04/28 12:07

首先我们需要先建立一个Bean: User

package cn.class3g.web.domain;public class User {private String username;private String password;public User() {super();// TODO Auto-generated constructor stub}public User(String username, String password) {super();this.username = username;this.password = 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;}}

然后我们建立用户登录界面login.jsp

  <form action="${pageContext.request.contextPath }/servlet/LoginServlet" method="post">   用户名：<input type="text" name="username"><br>   密码：<input type="password" name="password"><br>   <input type="submit" value="登录">   </form>

建立登录用户的Servlst LoginServlet

package cn.class3g.web.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.class3g.web.domain.User;public class LoginServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String username = request.getParameter("username");String password = request.getParameter("password");User user = new User(username,password);user.setUsername(username);user.setPassword(password);request.getSession().setAttribute("user",user);response.sendRedirect(request.getContextPath() +"/index.jsp");}}

接着我们还需要一个页面，用户登录成功页面index.jsp

欢迎你： ${user.username }<a href="${pageContext.request.contextPath }/servlet/QuitServlet?username=${user.username }">退出</a>这里的退出是现实用户的在线与离线状态

现在我们需要监听session中user对象的加入

package cn.class3g.web.listener;import java.util.HashMap;import java.util.Map;import javax.servlet.ServletContext;import javax.servlet.http.HttpSession;import javax.servlet.http.HttpSessionAttributeListener;import javax.servlet.http.HttpSessionBindingEvent;import cn.class3g.web.domain.User;public class SessionAttributeListener implements HttpSessionAttributeListener {public void attributeAdded(HttpSessionBindingEvent se) {// TODO Auto-generated method stubObject obj = se.getValue();if (obj instanceof User) {HttpSession session = se.getSession();ServletContext context = session.getServletContext();Map map = (Map) context.getAttribute("map");if (map == null) {map = new HashMap();context.setAttribute("map", map);}User user = (User) obj;map.put(user.getUsername(), session);}}public void attributeRemoved(HttpSessionBindingEvent se) {// TODO Auto-generated method stub}public void attributeReplaced(HttpSessionBindingEvent se) {// TODO Auto-generated method stub}}

接着需要建立一个用户显示界面listUser.jsp

 <body>    当前用户有：    <c:forEach var="me" items="${map }">    ${me.key }</c:forEach>这里我们需要用到标签

因为我们做的是一个在线用户的查询系统，所以我们要给用户一个退出，来现实用户的在线与离线QuitServlet

package cn.class3g.web.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 QuitServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String username = request.getParameter("username");Map map = (Map) this.getServletContext().getAttribute("map");HttpSession session = (HttpSession) map.get(username);if(session !=null){session.invalidate();map.remove(username);}request.getRequestDispatcher("/quit.jsp").forward(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}}