Servlet监听器定时监听在线用户生成列表

最新推荐文章于 2021-10-06 22:15:09 发布

原创最新推荐文章于 2021-10-06 22:15:09 发布 · 560 阅读

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本文介绍了一种使用Servlet监听器实现定时检查并更新用户在线状态的方法，通过创建监听类和执行任务类来实现对在线用户的实时监测，并在后台进行用户列表的更新。

1.创建监听的类，实现servlet监听的接口ServletContextListener，启动后创建定时执行方法

/FlexAppToJava/src/com/service/userList/UserCheckLinster.java

代码如下：

        package com.service.userList;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class UserCheckLinster implements ServletContextListener {

 private java.util.Timer timer = null ;
 @Override
 public void contextDestroyed(ServletContextEvent arg0) {
  // TODO Auto-generated method stub
 
 }

 @Override
 public void contextInitialized(ServletContextEvent event) {
  // TODO Auto-generated method stub
  timer = new java.util.Timer(true) ;
  timer.schedule(new MyTask(event.getServletContext()), 0, 5000);
 }

}

2.执行任务的类文件

/FlexAppToJava/src/com/service/userList/MyTask.java

代码如下：

package com.service.userList;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Set;
import java.util.TimerTask;

import javax.servlet.ServletContext;

public class MyTask extends TimerTask {

 private static boolean isRunning = false;
    private ServletContext context = null;
    private HashMap<String, Date> onLinehashMap=UserListData.getInstance().onLineUserMap;
 private HashMap<String, Date> downLineUserMap=UserListData.getInstance().downLineUserMap;
 private List<User> allUserList=UserListData.getInstance().allUserList;
   
 public MyTask(ServletContext servletContext) {
   this.context = servletContext ;
 }

 @Override
 public void run() {
  if (! isRunning){
                isRunning = true ;
               
                checkUserList();
                updateAllList();
         
                isRunning = false;
 
        }else{
             
        }

 }
 
 //-----------自定义方法--------------
 private void checkUserList(){
  Date nowDate=new Date();
  Set<String> keySet=onLinehashMap.keySet();
  for(String userName:keySet){
   Date lastDate=onLinehashMap.get(userName);
   long between=nowDate.getTime()-lastDate.getTime();
   if(between>1000*60*1){
    //
    onLinehashMap.remove(userName);
    downLineUserMap.put(userName, nowDate);
   }
  }
 }
 
 private void updateAllList(){
  List<User> newUserList=new ArrayList<User>();
  //
  Set<String> keySet=onLinehashMap.keySet();
  for(String userName:keySet){
   User user=new User();
   user.setUserName(userName);
   user.setDataTime(onLinehashMap.get(userName));
   user.setIsOnline(true);
   newUserList.add(user);
  }
  //
  keySet=downLineUserMap.keySet();
  for(String userName:keySet){
   User user=new User();
   user.setUserName(userName);
   user.setDataTime(onLinehashMap.get(userName));
   user.setIsOnline(false);
   newUserList.add(user);
  }
 
  allUserList.clear();
  allUserList.addAll(newUserList);
 }
 
}

3.存放缓存数据的类

/FlexAppToJava/src/com/service/userList/UserListData.java

代码如下：

package com.service.userList;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;

/**
 * 数据类
 * @author acer
 */
public class UserListData {
 
 private static UserListData userListData;
 
 
 public HashMap<String,Date> onLineUserMap=new HashMap<String,Date>();
 public HashMap<String,Date> downLineUserMap=new HashMap<String,Date>();
 public List<User> allUserList=new ArrayList<User>();
 
 
 
 private UserListData(){
 
 }
 public static UserListData getInstance(){
  if(userListData==null){
   userListData=new UserListData();
  }
  return userListData;
 }
}

4.javaBean类

/FlexAppToJava/src/com/service/userList/User.java

代码如下：

package com.service.userList;

import java.util.Date;

public class User {
 private String userName;
 private Date dataTime;
 private Boolean isOnline;
 public String getUserName() {
  return userName;
 }
 public void setUserName(String userName) {
  this.userName = userName;
 }
 public Date getDataTime() {
  return dataTime;
 }
 public void setDataTime(Date dataTime) {
  this.dataTime = dataTime;
 }
 public Boolean getIsOnline() {
  return isOnline;
 }
 public void setIsOnline(Boolean isOnline) {
  this.isOnline = isOnline;
 }
 
}

5.修改web.xml文件，添加

<listener>
     <listener-class>com.service.userList.UserCheckLinster</listener-class>
    </listener>