Java基于servlet监听器实现在线人数监控功能的方法
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2023-12-20 08:23:28
本文实例讲述了java基于servlet监听器实现在线人数监控功能的方法。分享给大家供大家参考,具体如下:
1、分析:
做一个网站在线人数统计,可以通过servletc...
本文实例讲述了java基于servlet监听器实现在线人数监控功能的方法。分享给大家供大家参考,具体如下:
1、分析:
做一个网站在线人数统计,可以通过servletcontextlistener监听,当web应用上下文启动时,在servletcontext中添加一个list.用来准备存放在线的用户名,然后通过httpsessionattributelistener监听,当用户登录成功,把用户名设置到session中。同时将用户名方法到servletcontext的list中,最后通过httpsessionlistener监听,当用户注销会话时,讲用户名从应用上下文范围中的list列表中删除。
2、注意事项
测试时,需要启动不同的浏览器来登陆不同的用户,只有点击注销按钮才能减少在线用户,关闭浏览器不能减少在线用户。
3、项目源代码
(1)java代码
onlinelistener类
package com.smalle.listener; import java.util.linkedlist; import java.util.list; import javax.servlet.servletcontext; import javax.servlet.servletcontextevent; import javax.servlet.servletcontextlistener; import javax.servlet.http.httpsessionattributelistener; import javax.servlet.http.httpsessionbindingevent; import javax.servlet.http.httpsessionevent; import javax.servlet.http.httpsessionlistener; public class onlinelistener implements servletcontextlistener, httpsessionattributelistener, httpsessionlistener { private servletcontext application = null; //应用上下文初始时会回调的方法 @override public void contextinitialized(servletcontextevent e) { //初始化一个application对象 application = e.getservletcontext(); //设置一个列表属性,用于保存在线用户名 this.application.setattribute("online", new linkedlist<string>()); } //往会话中添加属性时的回调方法 @override public void attributeadded(httpsessionbindingevent e) { //取得用户名列表 list<string> onlines = (list<string>) this.application.getattribute("online"); if("username".equals(e.getname())){ onlines.add((string) e.getvalue()); } //将添加后的列表重新设置列application属性中. this.application.setattribute("online", onlines); } //会话销毁时会回调的方法 @override public void sessiondestroyed(httpsessionevent e) { //取得用户名列表 list<string> onlines = (list<string>) this.application.getattribute("online"); //取得当前用户名 string username = (string) e.getsession().getattribute("username"); //将此用户从列表中删除 onlines.remove(username); //讲删除后的列表重新设置到application属性中. this.application.setattribute("online", onlines); } public void sessioncreated(httpsessionevent e) {} public void attributeremoved(httpsessionbindingevent e) {} public void attributereplaced(httpsessionbindingevent e) {} public void contextdestroyed(servletcontextevent e) {} }
loginservlet类
package com.smalle.listener; import java.io.ioexception; import java.io.printwriter; import java.util.list; import javax.servlet.servletexception; import javax.servlet.http.httpservlet; import javax.servlet.http.httpservletrequest; import javax.servlet.http.httpservletresponse; public class loginservlet extends httpservlet { private static final long serialversionuid = 1l; public void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { this.dopost(request, response); } public void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { request.setcharacterencoding("utf-8"); //设置响应内容类型 string username= request.getparameter("username"); //获取请求参数中的用户名 //往session中添加属性,会触发httpsessionattributelistener中的attributeadded方法 if(username != null && !username.equals("")) { request.getsession().setattribute("username",username); } //从应用上下文中获取在线用户名列表 list<string> online = (list<string>)getservletcontext().getattribute("online"); system.out.println("loginservlet" + online); response.setcontenttype("text/html;charset=utf-8"); printwriter out = response.getwriter(); out.println(""); out.println(" <title>用户列表</title>"); out.println(" "); out.println("当前用户是:" + username); out.print(" <hr><h3>在线用户列表</h3>"); int size = online == null ? 0 : online.size(); for (int i = 0; i < size; i++) { if(i > 0){ out.println("<br>"); } out.println(i + 1 + "." + online.get(i)); } //注意: 要对链接url进行自动重写处理 out.println("<hr/><a href=\"" + response.encodeurl("logoutlistener") + "\">注销</a>"); out.println(" "); out.println(""); out.flush(); out.close(); } }
logoutservlet类
package com.smalle.listener; import java.io.ioexception; import java.io.printwriter; import java.util.list; import javax.servlet.servletexception; import javax.servlet.http.httpservlet; import javax.servlet.http.httpservletrequest; import javax.servlet.http.httpservletresponse; public class logoutservlet 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 { request.setcharacterencoding("utf-8"); //设置响应内容类型 //销毁会话,会触发sessionlinstener中的sessiondestroyed方法 request.getsession().invalidate(); //从应用上下文中获取在线用户名列表 list<string> online = (list<string>)getservletcontext().getattribute("online"); response.setcontenttype("text/html;charset=utf-8"); printwriter out = response.getwriter(); out.println(""); out.println(" <title>用户列表</title>"); out.println(" "); out.print(" <h3>在线用户列表</h3>"); int size = online == null ? 0 : online.size(); for (int i = 0; i < size; i++) { if(i > 0){ out.println("<br>"); } out.println(i + 1 + "." + online.get(i)); } out.println("<hr><a href='\'index.html\''>主页</a>"); out.println(" "); out.println(""); out.flush(); out.close(); } }
(2)web.xml代码
<?xml version="1.0" encoding="utf-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/xmlschema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemalocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="webapp_id" version="3.0"> <display-name>testservlet</display-name> <listener> <listener-class>com.smalle.listener.onlinelistener</listener-class> </listener> <servlet> <servlet-name>loginservlet</servlet-name> <servlet-class>com.smalle.listener.loginservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>loginservlet</servlet-name> <url-pattern>/loginlistener</url-pattern> </servlet-mapping> <servlet> <servlet-name>logoutservlet</servlet-name> <servlet-class>com.smalle.listener.logoutservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>logoutservlet</servlet-name> <url-pattern>/logoutlistener</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
(3)表现层代码
<!doctype html> <html> <head> <title>index.html</title> <meta name="content-type" content="text/html; charset=utf-8"> </head> <body> <form action="loginlistener" method="post"> 用户名:<input type="text" name="username"> <input type="submit" value="登录"><br><br> </form> </body> </html>
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