servlet监听实现统计在线人数功能 附源码下载

本文实例为大家分享了servlet统计在线人数的具体代码，供大家参考，具体内容如下

ServletContext事件监听器---->针对applicationScope
ServletContextListener(*)
对整个Web应用的装载和卸载进行监听。
 ServletContextAttributeListener
对ServletContext中的信息存放、删除和替换进行监听。
ServletContext就是Servlet上下文监听，在web中表示的是对启动服务和销毁服务进行监听，需要实现的接口：
ServletContextListener接口，实现的就是对上下午进行监听：
void contextInitialized(ServletContextEvent sce)：启动上下文时的监听
void contextDestroyed(ServletContextEvent sce)：销毁上下文时进行的监听
除了对上下文的启动和销毁进行监听的之外，还可以对上下文的属性进行监听：ServletContextAttributeListener接口。
void attributeAdded(ServletContextAttributeEvent event)：设置上下文属性监听
void attributeRemoved(ServletContextAttributeEvent event)：移除上下文属性的监听
void attributeReplaced(ServletContextAttributeEvent event)：修改上下文属性的监听
ServletContextAttributeEvent：事件，可以通过事件取得属性的内容和名称。
·取得属性名称：public java.lang.String getName()
·取得属性的值：public java.lang.Object getValue()
效果如下图：

当登录一个账号时

打开另一个浏览器，再登录一个账号

如上图，我们可以看到，程序已经完成了统计在线人数和显示人员列表的功能，那么他的实现流程是什么呢？

我们可以通过ServletContextListener完成在线人数的统计和显示在线人数列表，首先listener和filter一样要在web.xml中进行描述。

代码如下：

<listener>
 <listener-class>net.jvsun.ListenerTest</listener-class>
</listener>

为了测试这个程序，我们也必须完成用户登录功能。
数据库连接帮助类：

public class JDBCHelper {
 public static final String DRIVER = "oracle.jdbc.driver.OracleDriver";
 public static final String URL = "jdbc:oracle:thin:@localhost:1521:xxx";
 public static final String DBNAME = "scott";
 public static final String PASSWORD = "xxx";
 public static Connection getConn() throws Exception{
 Class.forName(DRIVER);
 Connection conn = DriverManager.getConnection(URL, DBNAME, PASSWORD);
 return conn;
 }
}

用户实体类：

public class UserPOJO implements Serializable{
 private static final long serialVersionUID = 7554548269035753256L;
 private int id;
 private String username;
 private String password;
 public int getId() {
 return id;
 }
 public void setId(int id) {
 this.id = id;
 }
 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;
 }
 public UserPOJO(int id, String username, String password) {
 super();
 this.id = id;
 this.username = username;
 this.password = password;
 }
 public UserPOJO(String username, String password) {
 this.username = username;
 this.password = password;
 }
 public UserPOJO() {
 super();
 // TODO Auto-generated constructor stub
 } 

} 

数据库处理类：

public class UserDAO {
 public UserPOJO login(String username, String password) {
 UserPOJO user=null;
 Connection conn = null;
 PreparedStatement pstate = null;
 ResultSet res = null;
 try {
 conn=JDBCHelper.getConn();
 String sql="select id,username from userinfo where username=? and password=?";
 pstate = conn.prepareStatement(sql);
 pstate.setString(1, username);
 pstate.setString(2, password);
 res = pstate.executeQuery();
 while(res.next()){
 user=new UserPOJO(res.getInt(1),username,null);
 }
 } catch (Exception e) {
 e.printStackTrace();
 }finally{
 try {
 res.close();
 pstate.close();
 conn.close();
 } catch (SQLException e) {
 e.printStackTrace();
 } 

 }
 return user;
 }
} 

servlet类：

public class UserServlet extends HttpServlet{ 

 @Override
 protected void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 String path = request.getContextPath();
 response.setContentType("text/html; charset=utf-8");
 request.setCharacterEncoding("utf-8");
 String username = request.getParameter("username");
 String password = request.getParameter("password");
 ServletContext application = this.getServletContext();//取得application对象
 List<String> list = (List<String>) application.getAttribute("allUser");
 if(list.indexOf(username) == -1){
 UserPOJO pojo = new UserDAO().login(username, password);
 if(null != pojo){
 HttpSession session = request.getSession(true);//取得session对象
 session.setAttribute("userName", username);
 } 

 }
 response.sendRedirect(path+"/index.jsp");
 } 

 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp)
 throws ServletException, IOException {
 doGet(req, resp);
 } 

} 

监听类：

public class ListenerTest implements ServletContextListener,HttpSessionAttributeListener,HttpSessionListener{
 ServletContext application = null;
 public void contextDestroyed(ServletContextEvent event) {
 System.out.println("服务器关闭");
 } 

 public void contextInitialized(ServletContextEvent event) {
 List<String> list = new ArrayList<String>();
 //用来保存所有已登录的用户
 application = event.getServletContext();
 //取得application对象
 application.setAttribute("allUser", list);
 //将集合设置到application范围属性中去 

 } 

 public void attributeAdded(HttpSessionBindingEvent se) {
 List<String> list = (List<String>)application.getAttribute("allUser");
 //假设：用户登陆成功之后，只将户名设置到session中
 String userName = (String)se.getValue();
 //取得用户名
 if(list.indexOf(userName) == -1){
 //表示此用户之前没有登陆
 list.add(userName);
 application.setAttribute("allUser", list);
 }
 } 

 public void attributeRemoved(HttpSessionBindingEvent se) {
 List<String> list = (List<String>)application.getAttribute("allUser");
 list.remove((String)se.getValue());
 application.setAttribute("allUser", list);
 } 

 public void attributeReplaced(HttpSessionBindingEvent se) { 

 } 

 public void sessionCreated(HttpSessionEvent event) { 

 } 

 public void sessionDestroyed(HttpSessionEvent event) { 

 }
} 

登录页面

<%@page contentType="text/html; charset=utf-8"%>
<%@page import="java.util.*" %>
<%
 String path = request.getContextPath();
 %> 

<html>
 <body> 

 <form action="<%=path %>/Login" method="post">
 账号：
 <input type="text" name="username" />
 <br />
 密码：
 <input type="password" name="password" />
 <br />
 <input type="submit" value="提交" />
 </form> 

 </body> 

</html> 

显示在线人数和在线人员的列表界面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%> 

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" >
 <title></title>
 </head> 

 <body>
 <ul>
 <%
 System.out.println(application.getAttribute("allUser"));
 if(null != application.getAttribute("allUser")){
 List<String> list = (List<String>)application.getAttribute("allUser");
 %>
 <h2>在线人数:<%=list.size() %></h2>
 <%
 for(String s:list){
 %>
 <a>姓名：</a><%=s %><a>---->此时在线</a><br> 

 <%
 }
 }
 %>
 </ul>
 <hr/>
 <a href="<%=path %>/logout.jsp" rel="external nofollow" >注销</a>
 </body>
</html> 

注销界面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%> 

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" >
 <title>logout</title>
 </head>
 <body>
 <%
 session.removeAttribute("username");
 session.invalidate();
 response.sendRedirect("login.jsp");
 %>
 </body>
</html>

代码下载地址：servlet统计在线人数

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