关键字: httpsession
1.http://www.jspcn.net/htmlnews/11049329478121583.html 监听器
2.session.invalidate() ,session才会destroy
3.HttpSessionListener: 这个监听取不到session里面的值
在线列表实例
下面的代码可以获取上线,下线的在线列表 :
public class OnlineListener implements HttpSessionListener ,HttpSessionAttributeListener{
public void sessionCreated(HttpSessionEvent event) {//只要一打开浏览器就会执行 ,没有登陆也会执行.
}
public void sessionDestroyed(HttpSessionEvent event) {//只有超时,invalidate()才会执行
HttpSession se=event.getSession(); OnlineManager.getInstance().removeSession(se); //从列表中删除 // System.out.println("remove session....................");//为什么浏览窗口关闭了,没有执行啊??? }public void attributeAdded(HttpSessionBindingEvent event) {//如果登陆成功, 就把上线 用户添加 到列表.
HttpSession se=event.getSession(); String name=event.getName(); String value=(String)event.getValue(); if("username".equals(name)){ OnlineManager.getInstance().addSession(se); //添加 } }}
public class OnlineManager {
private static OnlineManager om;
private Map<String,HttpSession> sessions; private OnlineManager(){ sessions=new HashMap<String,HttpSession>();//为什么没有共用一个sessions; } public static OnlineManager getInstance(){ if(om==null){ om=new OnlineManager(); } return om; } public void addSession(HttpSession se){ String key=(String)se.getAttribute("username"); sessions.put(key, se); System.out.println("add 1 : "+sessions.size()); } public void removeSession(HttpSession se){ String key=(String)se.getAttribute("username"); //sessions.remove(key); //这个只是把key=null sessions.remove(sessions.get(key)); System.out.println("remove 1 : " +"key:"+key+sessions.size()); System.out.println(sessions); }}------------------------第二种方法实现在线,下线:
public class BindSession implements HttpSessionBindingListener {
private String username; public BindSession(String username){ this.username=username; } public void valueBound(HttpSessionBindingEvent event) { HttpSession session = event.getSession(); // String name=(String)session.getAttribute("name"); ServletContext application = session.getServletContext();// 把用户名放入在线列表
List onlineUserList = (List) application.getAttribute("onlineUserList"); // 第一次使用前，需要初始化 if (onlineUserList == null) { onlineUserList = new ArrayList(); application.setAttribute("onlineUserList", onlineUserList); } onlineUserList.add(this.username); System.out.println("valueBound: .........."+onlineUserList.size()); }public void valueUnbound(HttpSessionBindingEvent event) {
HttpSession session = event.getSession(); // String name=(String)session.getAttribute("name"); ServletContext application = session.getServletContext();// 从在线列表中删除用户名
List onlineUserList = (List) application.getAttribute("onlineUserList"); onlineUserList.remove(this.username);System.out.println(this.username + "退出。");
}}
public class Login extends HttpServlet {
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException { String name=req.getParameter("name"); String pass=req.getParameter("password"); boolean isLogin=false; int len=set.size(); for(int i=0;i<len;i++){ if(set.containsKey(name)&&set.containsValue(pass)){ isLogin=true; } } if(isLogin){ req.getSession().setAttribute("username", name); System.out.println("login ...username="+name); //BindListener 的使用: BindSession bl=new BindSession(name); req.getSession().setAttribute("lis", bl); resp.sendRedirect("index.jsp"); } else{ resp.sendRedirect("login.jsp"); }