servlet监听实现统计在线人数功能 附源码下载

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：

net.jvsun.ListenerTest

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.usernamhttp://e = 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 list = (List) 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 list = new ArrayList();

//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 list = (List)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 list = (List)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();

%>

账号：

密码：

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+"/";

%>

<%

System.out.println(application.getAttribute("allUser"));

if(null != application.getAttribute("allUser")){

List list = (List)application.getAttribute("allUser");

%>

<%

for(String s:list){

%>

姓名：<%=s %>---->此时在线

<%

}

}

%>

注销

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+"/";

%>

<%

session.removeAttribute("username");

session.invalidate();

response.sendRedirect("login.jsp");

%>

代码下载地址：servlet统计在线人数

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