servlet監(jiān)聽實現(xiàn)統(tǒng)計在線人數(shù)功能附源碼下載

更新時間：2017年04月14日 14:26:23 作者：阿木俠

這篇文章主要為大家詳細介紹了servlet監(jiān)聽統(tǒng)計在線人數(shù)的實現(xiàn)方法，文中示例代碼介紹的非常詳細，具有一定的參考價值，感興趣的小伙伴們可以參考一下

本文實例為大家分享了servlet統(tǒng)計在線人數(shù)的具體代碼，供大家參考，具體內(nèi)容如下

ServletContext事件監(jiān)聽器---->針對applicationScope
ServletContextListener(*)
對整個Web應(yīng)用的裝載和卸載進行監(jiān)聽。
ServletContextAttributeListener
對ServletContext中的信息存放、刪除和替換進行監(jiān)聽。
ServletContext就是Servlet上下文監(jiān)聽，在web中表示的是對啟動服務(wù)和銷毀服務(wù)進行監(jiān)聽，需要實現(xiàn)的接口：
ServletContextListener接口，實現(xiàn)的就是對上下午進行監(jiān)聽：
void contextInitialized(ServletContextEvent sce)：啟動上下文時的監(jiān)聽
void contextDestroyed(ServletContextEvent sce)：銷毀上下文時進行的監(jiān)聽
除了對上下文的啟動和銷毀進行監(jiān)聽的之外，還可以對上下文的屬性進行監(jiān)聽：ServletContextAttributeListener接口。
void attributeAdded(ServletContextAttributeEvent event)：設(shè)置上下文屬性監(jiān)聽
void attributeRemoved(ServletContextAttributeEvent event)：移除上下文屬性的監(jiān)聽
void attributeReplaced(ServletContextAttributeEvent event)：修改上下文屬性的監(jiān)聽
ServletContextAttributeEvent：事件，可以通過事件取得屬性的內(nèi)容和名稱。
·取得屬性名稱：public java.lang.String getName()
·取得屬性的值：public java.lang.Object getValue()

效果如下圖：

當?shù)卿浺粋€賬號時

打開另一個瀏覽器，再登錄一個賬號

如上圖，我們可以看到，程序已經(jīng)完成了統(tǒng)計在線人數(shù)和顯示人員列表的功能，那么他的實現(xiàn)流程是什么呢？

我們可以通過ServletContextListener完成在線人數(shù)的統(tǒng)計和顯示在線人數(shù)列表，首先listener和filter一樣要在web.xml中進行描述。

代碼如下：

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

為了測試這個程序，我們也必須完成用戶登錄功能。
數(shù)據(jù)庫連接幫助類：

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; 
 } 
}

用戶實體類：

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 
 } 
 
}

數(shù)據(jù)庫處理類：

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類：

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對象 
 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對象 
 session.setAttribute("userName", username); 
 } 
 
 } 
 response.sendRedirect(path+"/index.jsp"); 
 } 
 
 @Override 
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) 
 throws ServletException, IOException { 
 doGet(req, resp); 
 } 
 
}

監(jiān)聽類：

public class ListenerTest implements ServletContextListener,HttpSessionAttributeListener,HttpSessionListener{ 
 ServletContext application = null; 
 public void contextDestroyed(ServletContextEvent event) { 
 System.out.println("服務(wù)器關(guān)閉"); 
 } 
 
 public void contextInitialized(ServletContextEvent event) { 
 List<String> list = new ArrayList<String>(); 
 //用來保存所有已登錄的用戶 
 application = event.getServletContext(); 
 //取得application對象 
 application.setAttribute("allUser", list); 
 //將集合設(shè)置到application范圍屬性中去 
 
 } 
 
 public void attributeAdded(HttpSessionBindingEvent se) { 
 List<String> list = (List<String>)application.getAttribute("allUser"); 
 //假設(shè)：用戶登陸成功之后，只將戶名設(shè)置到session中 
 String userName = (String)se.getValue(); 
 //取得用戶名 
 if(list.indexOf(userName) == -1){ 
 //表示此用戶之前沒有登陸 
 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) { 
 
 } 
}

登錄頁面

<%@page contentType="text/html; charset=utf-8"%> 
<%@page import="java.util.*" %> 
<% 
 String path = request.getContextPath(); 
 %> 
 
<html> 
 <body> 
 
 <form action="<%=path %>/Login" method="post"> 
 賬號： 
 <input type="text" name="username" /> 
 <br /> 
 密碼： 
 <input type="password" name="password" /> 
 <br /> 
 <input type="submit" value="提交" /> 
 </form> 
 
 </body> 
 
</html>

顯示在線人數(shù)和在線人員的列表界面

<%@ 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>在線人數(shù):<%=list.size() %></h2> 
 <% 
 for(String s:list){ 
 %> 
 <a>姓名：</a><%=s %><a>---->此時在線</a><br> 
 
 <% 
 } 
 } 
 %> 
 </ul> 
 <hr/> 
 <a href="<%=path %>/logout.jsp" rel="external nofollow" >注銷</a> 
 </body> 
</html>

注銷界面：

<%@ 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>

代碼下載地址：servlet統(tǒng)計在線人數(shù)

以上就是本文的全部內(nèi)容，希望對大家的學習有所幫助，也希望大家多多支持腳本之家。

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