Spring boot通过HttpSessionListener监听器统计在线人数的实现代码

@WebListener 
public class SessionListener implements HttpSessionListener{ 
public void sessionCreated(HttpSessionEvent arg0) { 
// TODO Auto-generated method stub 
ServletContext context = arg0.getSession().getServletContext(); 
if (context.getAttribute("count")==null) { 
context.setAttribute("count", 0); 
}else { 
int count = (Integer) context.getAttribute("count"); 
context.setAttribute("count", count+1); 
} 
} 
public void sessionDestroyed(HttpSessionEvent arg0) { 
// TODO Auto-generated method stub 
ServletContext context = arg0.getSession().getServletContext(); 
if (context.getAttribute("count")==null) { 
context.setAttribute("count", 0); 
}else { 
int count = (Integer) context.getAttribute("count"); 
if (count<1) { 
count = 1; 
} 
context.setAttribute("count", count-1); 
} 
HttpSession session = arg0.getSession(); 
String name = (String) session.getAttribute("name"); 
HashSet<String> nameSet = (HashSet<String>) context.getAttribute("nameSet"); 
nameSet.remove(name); 
} 
} 

HttpSession session = request.getSession(); 
session.setAttribute("name", name); 
Object count = context.getAttribute("count"); 
if (count==null) { 
count = 0; 
} 

<listener> 
  <listener-class>zjq.listener.SessionListener</listener-class> 
 </listener>