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

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 sessions;

private OnlineManager(){

sessions=new HashMap();//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

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");

}