Spring boot implements the implementation code for counting the number of online users through the HttpSessionListener listener

First of all, this statistics has a flaw in the number of people online. One person can have multiple sessions at the same time, resulting in certain inaccurate statistics.

Next, start writing the code.

Step 1: Implement the method in HttpSessionListener, add the annotation @WebListener

 @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); } }

Step 2: Control the creation of session and put it into the object

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

Step 3: Start the class with the annotation @ServletComponentScan, so that you can scan to the listener

Note, this code is suitable for spring-boot development

Simply put, add a listener in javaWeb to web.xml

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

Summarize

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