JaveWeb统计在线人数

实现功能：

1.当用户没有登录的时候，自动给他分配name=游客***。

2.当用户登录后，自动把name替换成用户名(username)

3.当点击注销时，把用户名(username)替换成name=游客***

   

 具体实现：

1.用application监听来实现统计在线用户

2.用session监听来实现分配name=游客**和用户注销

 现有t_user表有id，username，password字段

1.写一个application监听MyServletContextListener

public class MyServletContextListener implements ServletContextListener {public void contextDestroyed(ServletContextEvent event) {}public void contextInitialized(ServletContextEvent event) {//创建onlinePersonList<String> onlinePerson =new ArrayList<String>();//获取applicationServletContext application = event.getServletContext();//保存onlinePersonapplication.setAttribute("onlinePerson",onlinePerson );}}

2.写一个session监听MySession

public class MySessionListener implements HttpSessionListener {public void sessionCreated(HttpSessionEvent event) {HttpSession session = event.getSession();//随机给浏览器创建一个用户名String onlineName = "游客"+new SimpleDateFormat("HHmmss").format(new Date());session.setAttribute("onlineName", onlineName);//获取applicationServletContext application = event.getSession().getServletContext();List<String> onlinePerson = (List<String>) application.getAttribute("onlinePerson");//把onlineName添加到onlinePerson中去onlinePerson.add(onlineName);//添加到application中去application.setAttribute("onlinePerson", onlinePerson);}public void sessionDestroyed(HttpSessionEvent event) {//获取sessionHttpSession session = event.getSession();//获取随机分配给浏览器的nameString onlineName = (String) session.getAttribute("onlineName");//获取application并得到onlinePersonList<String> onlinePerson = (List<String>) session.getServletContext().getAttribute("onlinePerson");//索引int index=-1;//迭代出onlinePerson,判断onlineName是否一样for(Iterator<String> i = onlinePerson.iterator();i.hasNext();){index++;//判断name名是否一样if(i.next().equals(onlineName)){break;}}//把username移除掉onlinePerson.remove(index);}}

3.在登录servlet(login.do)中

User user = UserServiceImpl.getInstance().login(username, password);request.getSession().setAttribute("user", user);HttpSession session = request.getSession();String onlineName = (String) session.getAttribute("onlineName");List<String> onlinePerson = (List<String>) request.getSession().getServletContext().getAttribute("onlinePerson");int index=-1;//迭代出onlinePerson,判断onlineName是否一样for(Iterator<String> i = onlinePerson.iterator();i.hasNext();){index++;if(i.next().equals(onlineName)){break;    }   }//替换出usernameonlinePerson.set(index, username);request.getSession().getServletContext().setAttribute("onlinePerson", onlinePerson);

4.在注销servlet(logout.do)中

HttpSession session = request.getSession();//调用destroy方法session.invalidate();//重定向到首页response.sendRedirect("./index.jsp");

5.在index.jsp中登录超链接到login.do，注销超链接到logout.do

        <%         //获取onlinePerson

List<String> onlinePerson = (List<String>)application.getAttribute("onlinePerson");         %>         在线人数：<%=onlinePerson.size() %>         <% 

//迭代出onlinePerson,并输出         for(Iterator<String> i = onlinePerson.iterator();i.hasNext();){         %>                  <%=i.next() %>                  <% }%>         

6.部署，显示效果