1.配置监听器
package listener;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class OnlineListener implements HttpSessionListener {
@Override
public void sessionCreated(HttpSessionEvent se) {
ServletContext sc = se.getSession().getServletContext();
Integer onlineCount = (Integer) sc.getAttribute("OnlineCount");
if (onlineCount==null){
onlineCount=-1;
}else{
onlineCount+=1;
}
sc.setAttribute("OnlineCount",onlineCount);
}
@Override
public void sessionDestroyed(HttpSessionEvent se) {
ServletContext sc = se.getSession().getServletContext();
Integer onlineCount = (Integer) sc.getAttribute("OnlineCount");
if (onlineCount==null){
onlineCount=0;
}else{
onlineCount=onlineCount-1;
}
sc.setAttribute("OnlineCount",onlineCount);
}
}
2.配置web.xml
<listener>
<listener-class>listener.OnlineListener</listener-class>
</listener>
3.配置jsp
<h2>当前在线人数:
<%=pageContext.getSession().getServletContext().getAttribute("OnlineCount")%>
</h2>