东舟 — Fri, 26 Jan 2007 05:42:00 GMT

当用��L��录时�l�护一个会话对象：UserInfo�cȝ��实例�Q�同时UserInfo�c�d��现javax.servlet.http.HttpSessionBindingListener接口:
import JAVA.util.Map;
import JAVA.util.HashMap;
import javax.servlet.http.*;
import javax.servlet.ServletContext;

public class UserInfo implements HttpSessionBindingListener {
// 用户信息
int userId;
String userName;
......

/**
* 当UserInfo�c�被�l�定到session中时触发�q�个事�g
* 具体信息请参见Servlet/JSPs的规�?
*/
public void valueBound(HttpSessionBindingEvent event) {
HttpSession session = event.getSession ();
ServletContext ctx = session.getServletContext ();
Map map = (Map)ctx.getAttribute ("users");
if (map == null) { // 如果是服务器启动后的�W�一个登录用��P��新徏一个容�?
map = new HashMap ();
ctx.setAttribute ("users", map);
}

map.put (userName, this); // 把自己加入容器中
}

/**
* 当UserInfo�c�M��session中删除时触发�q�个事�g
* 具体信息请参见Servlet/JSPs的规�?
*/
public void valueUnbound(HttpSessionBindingEvent event) {
HttpSession session = event.getSession ();
ServletContext ctx = session.getServletContext ();
Map map = (Map)ctx.getAttribute ("users");
map.remove (this.userName); // 把自�׃��容器中删�?
}

......
}

以后在JSP中就可以�q�样昄��在线用户��C��Q?
<%
int userCount = 0;
JAVA.util.Map map = (java.util.Map)application.getAttribute ("users");
if (map == 0) userCount = 0;
else userCount = map.size ();
%>;

东舟 2007-01-26 13:42 发表评论

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