java web监听器统计在线用户及人数

<session-config>   <session-timeout>1</session-timeout> </session-config> 

package com.scx.entity; /**  * 用户实体类  *  */ public class User {   //当前用户的session id   private String sessionId;   //当前用户的ip地址   private String ip;   //当前用户第一次访问的时间   private String firstTime;   public User() {     super();   }   public String getIp() {     return ip;   }   public void setIp(String ip) {     this.ip = ip;   }   public String getFirstTime() {     return firstTime;   }   public void setFirstTime(String firstTime) {     this.firstTime = firstTime;   }   public String getSessionId() {     return sessionId;   }   public void setSessionId(String sessionId) {     this.sessionId = sessionId;   } } 

package com.scx.listener; import java.util.ArrayList; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; import com.scx.entity.User; import com.scx.util.SessionUtil; /**  * HttpSessionListener 监听器  *  */ @WebListener public class MyHttpSessionListener implements HttpSessionListener{   //当前用户数   private int userCounts=0;   @Override   public void sessionCreated(HttpSessionEvent se) {     //sessionCreated 用户数+1     userCounts++;     //重新在servletContext中保存userCounts     se.getSession().getServletContext().setAttribute("userCounts", userCounts);   }   @Override   public void sessionDestroyed(HttpSessionEvent se) {     //sessionDestroyed 用户数-1     userCounts--;     //重新在servletContext中保存userCounts     se.getSession().getServletContext().setAttribute("userCounts", userCounts);     @SuppressWarnings("unchecked")     ArrayList<User> userList=(ArrayList<User>) se.getSession().getServletContext().getAttribute("userList");     String sessionId=se.getSession().getId();     //如果当前用户在userList中 在session销毁时 将当前用户移出userList     if(SessionUtil.getUserBySessionId(userList, sessionId)!=null){       userList.remove(SessionUtil.getUserBySessionId(userList, sessionId));     }     //将userList集合 重新保存到servletContext     se.getSession().getServletContext().setAttribute("userList", userList);   } } 

package com.scx.listener; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Date; import javax.servlet.ServletRequestEvent; import javax.servlet.ServletRequestListener; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpServletRequest; import com.scx.entity.User; import com.scx.util.SessionUtil; /**  * ServletRequestListener 监听器  *  */ @WebListener public class MyServletRequestListener implements ServletRequestListener {   //用户集合   private ArrayList<User> userList;   @Override   public void requestDestroyed(ServletRequestEvent arg0) {   }   @SuppressWarnings("unchecked")   @Override   public void requestInitialized(ServletRequestEvent arg0) {     //从servletContext中获的userList     userList=(ArrayList<User>) arg0.getServletContext().getAttribute("userList");     //如果servletContext中没有userList对象 初始化userList     if(userList==null){       userList=new ArrayList<User>();     }     HttpServletRequest request=(HttpServletRequest) arg0.getServletRequest();     //sessionId     String sessionId=request.getSession().getId();     //如果当前sessionId不存在集合中 创建当前user对象     if(SessionUtil.getUserBySessionId(userList,sessionId)==null){       User user=new User();       user.setSessionId(sessionId);       user.setIp(request.getRemoteAddr());       SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd hh:MM:ss");       user.setFirstTime(sdf.format(new Date()));       userList.add(user);     }     //将userList集合 保存到ServletContext     arg0.getServletContext().setAttribute("userList", userList);   } } 

package com.scx.util; import java.util.ArrayList; import com.scx.entity.User; public class SessionUtil {   //根据sessionId判断当前用户是否存在在集合中 如果存在 返回当前用户 否则返回null   public static User getUserBySessionId(ArrayList<User> userList,String sessionId) {     for (User user : userList) {       if(sessionId.equals(user.getSessionId())){         return user;       }     }     return null;   } }