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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