servlet统计在线人数

CountServlet.java

@WebServlet("/CountServlet")
public class CountServlet extends HttpServlet implements HttpSessionListener,
        HttpSessionAttributeListener,HttpSessionBindingListener {
    private static final long serialVersionUID = 1L;
    private static int sessionCounter = 0;
    private static int attributeCounter = 0;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    public static int getOnlineSession() {
        return sessionCounter;
    }
    public static int getOnlineAttribute() {
        return attributeCounter;
    }

    @Override
    public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
        attributeCounter++;
        System.out.println("attribute added");
    }

    @Override
    public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
        attributeCounter--;
        System.out.println("attribute removed");
    }

    @Override
    public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {
        System.out.println(httpSessionBindingEvent.getName()+" replaced");
    }

    @Override
    public void valueBound(HttpSessionBindingEvent httpSessionBindingEvent) {
        System.out.println(httpSessionBindingEvent.getName()+"_Bound_" + httpSessionBindingEvent.getValue());
    }

    @Override
    public void valueUnbound(HttpSessionBindingEvent httpSessionBindingEvent) {
        System.out.println(httpSessionBindingEvent.getName()+"_Unbound_" + httpSessionBindingEvent.getValue());
    }

    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        sessionCounter++;
        System.out.println("session created");
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        sessionCounter--;
        System.out.println("session destroied");
    }
}

web.xml

    servlet.CountServlet

count.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="servlet.CountServlet"%>

  
    
  
  
  

      

          

              当前在线人数: <%= CountServlet.getOnlineSession() %> 人