Example of using Listener to implement global statistics on the website

1. Website global statistical variable class, only define global variables

 1 package com.lt.listener; 2  3 import java.util.Date; 4 import java.util.HashMap; 5 import java.util.Map; 6  7 import javax.servlet.http.HttpSession; 8 /** 9  * 网站全局变量类10  * @author LIUTIE11  *12  */13 public abstract class ApplicationConstants {14     15     /**16      * 用户登录session名称17      */18     public static final String LOGIN_SESSION_NAME = "userInfo";19 20     /**21      * 索引所有的session  
22      * 用于单一登录23      */24     public static Map<String,HttpSession> SESSION_MAP = new HashMap<>();25     26     /**27      * 当前在线用户数28      */29     public static int CURRENT_LOGIN_COUNT = 0;30     31     /**32      * 历史访客总数33      */34     public static int TOTAL_HISTORY_COUNT = 0;35     36     /**37      * 最高同时在线人数38      */39     public static int MAX_ONLINE_COUNT = 0;40     41     /**42      * 服务器启动时间43      */44     public static Date SERVER_START_DATE = new Date();45     46     /**47      * 最高在线人数时间48      */49     public static Date MAX_ONLINE_COUNT_DATE = new Date();50     51     52     53 }

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2. Implement servletContext monitoring to record server information

 1 package com.lt.listener; 2  3 import java.util.Date; 4  5 import javax.servlet.ServletContextEvent; 6 import javax.servlet.ServletContextListener; 7  8 /** 9  * servletContext监听10  * 记录服务器信息 启动关闭时间等11  * @author LIUTIE12  *13  */14 public class MyContextListener implements ServletContextListener {15 16     /**17      * 服务器启动时被调用18      */19     @Override20     public void contextDestroyed(ServletContextEvent arg0) {21         //记录启动时间22         ApplicationConstants.SERVER_START_DATE = new Date();23     }24 25     /**26      * 服务器关闭时被调用27      */28     @Override29     public void contextInitialized(ServletContextEvent arg0) {30         //保存数据到硬盘31         // TODO Auto-generated method stub32     }33 34 }

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3. Implement HttpSessionListener, HttpSessionAttributeListener monitoring, which is used to record login information, total number of visitors, number of people online, and realize single login, etc.

  1 package com.lt.listener;  2   3 import java.util.Date;  4   5 import javax.servlet.http.HttpSession;  6 import javax.servlet.http.HttpSessionAttributeListener;  7 import javax.servlet.http.HttpSessionBindingEvent;  8 import javax.servlet.http.HttpSessionEvent;  9 import javax.servlet.http.HttpSessionListener; 10  11 /** 12  * session监听 13  * 记录登录信息 访问总人数 在线人数等 14  * 实现单一登录 15  * @author LIUTIE 16  * 17  */ 18 public class MySessionListener implements HttpSessionListener, HttpSessionAttributeListener { 19  20     /** 21      * session创建时被调用 22      */ 23     @Override 24     public void sessionCreated(HttpSessionEvent sessionEvent) { 25         // 获取创建的session 26         HttpSession session = sessionEvent.getSession(); 27         // 添加到map 28         ApplicationConstants.SESSION_MAP.put(session.getId(), session); 29         // 访问总人数++ 30         ApplicationConstants.TOTAL_HISTORY_COUNT++; 31         // 如果map总数大于最高同时在线人数则更新最高在线人数及时间 32         if (ApplicationConstants.MAX_ONLINE_COUNT < ApplicationConstants.SESSION_MAP.size()) { 33             ApplicationConstants.MAX_ONLINE_COUNT = ApplicationConstants.SESSION_MAP.size(); 34             ApplicationConstants.MAX_ONLINE_COUNT_DATE = new Date(); 35         } 36  37     } 38  39     /** 40      * session销毁时被调用 41      */ 42     @Override 43     public void sessionDestroyed(HttpSessionEvent sessionEvent) { 44         // 获取即将被销毁的session 45         HttpSession session = sessionEvent.getSession(); 46         // 在map中根据key移除 47         ApplicationConstants.SESSION_MAP.remove(session.getId()); 48     } 49  50     /** 51      * 添加session属性时被调用 52      */ 53     @Override 54     public void attributeAdded(HttpSessionBindingEvent event) { 55         // 判断是否添加的用户登录信息session 56         if (event.getName().equals(ApplicationConstants.LOGIN_SESSION_NAME)) { 57             // 当前登录用户数++ 58             ApplicationConstants.CURRENT_LOGIN_COUNT++; 59             // 是否在其他机器登录处理 60             isLoginInOtherPlace(event); 61         } 62     } 63  64     /** 65      * 移除session属性时被调用 66      */ 67     @Override 68     public void attributeRemoved(HttpSessionBindingEvent event) { 69         // 判断是否移除的用户登录信息session 70         if (event.getName().equals(ApplicationConstants.LOGIN_SESSION_NAME)) { 71             // 当前登录用户数-- 72             ApplicationConstants.CURRENT_LOGIN_COUNT--; 73             // 是否在其他机器登录处理 74             isLoginInOtherPlace(event); 75         } 76     } 77  78     /** 79      * 修改session属性时被调用 80      */ 81     @Override 82     public void attributeReplaced(HttpSessionBindingEvent event) { 83  84         // 判断是否修改的用户登录信息session 85         if (event.getName().equals(ApplicationConstants.LOGIN_SESSION_NAME)) { 86             // 是否在其他机器登录处理 87             isLoginInOtherPlace(event); 88         } 89     } 90  91     /** 92      * 是否在其他机器登录处理 93      * 
 94      * @param event 95      */ 96     private void isLoginInOtherPlace(HttpSessionBindingEvent event) { 97         // 获取添加的session 98         HttpSession session = event.getSession(); 99         // 遍历查找此用户是否登录100         for (HttpSession s : ApplicationConstants.SESSION_MAP.values()) {101             // 如果已经在其他机器登录则使其失效102             if (event.getValue().equals(s.getAttribute(ApplicationConstants.LOGIN_SESSION_NAME))103                     && session.getId() != s.getId()) {104                 // 使session失效105                 session.invalidate();106                 break;107             }108         }109     }110 }

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4. Implement request monitoring to record customer information ip, url, etc.

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 1 package com.lt.listener; 2  3 import javax.servlet.ServletRequestEvent; 4 import javax.servlet.ServletRequestListener; 5 import javax.servlet.http.HttpServletRequest; 6  7 /** 8  * request监听 用于记录客户信息 ip、url等 9  * 
10  * @author LIUTIE11  *12  */13 public class MyRequestListener implements ServletRequestListener {14 15     /**16      * request销毁时调用17      */18     @Override19     public void requestDestroyed(ServletRequestEvent event) {20         // TODO Auto-generated method stub21 22     }23 24     /**25      * request创建时调用26      */27     @Override28     public void requestInitialized(ServletRequestEvent event) {29         HttpServletRequest request = (HttpServletRequest) event;30         // 客户端ip31         String ip = request.getRemoteAddr();32         // 访问的URL地址33         String url = request.getRequestURI();34         // 只做简单后台打印35         System.out.println("The client ip is " + ip);36         System.out.println("The address url is " + url);37     }38 39 }

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5. Configure a line of listener in web.xml

        <listener><listener-class>com.lt.listener.MyContextListener</listener-class></listener><listener><listener-class>com.lt.listener.MySessionListener</listener-class></listener><listener><listener-class>com.lt.listener.MyRequestListener</listener-class></listener>

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Listener Category:

1. Listener that monitors the creation and destruction of objects:

HttpSessionListener: sessionCreated(HttpSessionEvent sessionEvent), sessionDestroyed(HttpSessionEvent sessionEvent)

ServletRequestListener: requestInitialized(ServletRequestEvent event ), requestDestroyed(ServletRequestEvent event)

ServletContextListener: contextInitialized(ServletContextEvent event), contextDestroyed(ServletContextEvent event)

2. Listener that listens for changes in the properties of the object:

HttpSessionAttributeListener: (Triggered when adding, updating, or removing a session)

attributeAdded(HttpSessionBindingEvent event), attributeReplaced(HttpSessionBindingEvent event), attributeRemoved(HttpSessionBindingEvent event)

ServletContextAttributeListener: (add, update, remove context Triggered when)

attributeAdded(ServletContextAttributeEvent event), attributeReplaced(ServletContextAttributeEvent event), attributeRemoved(ServletContextAttributeEvent event)

ServletRequestAttributeListener: (triggered when adding, updating, or removing a request)

AttributeAdded(ServletRequestAttributeEvent event), attributeReplaced(ServletRequestAttributeEvent event), attributeRemoved(ServletRequestAttributeEvent event)

3. Monitor objects in Session

HttpSessionBindingListener: (Object is put into session, object is removed from session Triggered when)

ValueBound(HttpSessionBindingEvent event), valueUnbound(HttpSessionBindingEvent event)

HttpSessionActivationListener: (Triggered when the object in the session is passivated or the object is reloaded ps: the content in the session The process of saving to the hard disk is called passivation. Passivation requires the implementation of Serializable serialization interface)

sessionWillPassivate(HttpSessionEvent event), sessionDidActivate(HttpSessionEvent event)