如何在jsp用js检查session是否存在，

1. 一般的, session 是通过 cookie 来维持的, cookie 的名字可以通过配置指定一个名称
       mode="[Off|InProc|StateServer|SQLServer|Custom]"
       timeout="number of minutes"
       cookieName="session identifier cookie name"
       cookieless=
           "[true|false|AutoDetect|UseCookies|UseUri|UseDeviceProfile]"
       regenerateExpiredSessionId="[True|False]"
       sqlConnectionString="sql connection string"
       sqlCommandTimeout="number of seconds"
       allowCustomSqlDatabase="[True|False]"
       useHostingIdentity="[True|False]"
       stateConnectionString="tcpip=server:port"
       stateNetworkTimeout="number of seconds"
       customProvider="custom provider name">
       ...
   

2. 在 js 中可以判断这个名称的 cookie 是否存在.

3. function getCookie(name) {
       var cookies = document.cookie.split(";");
       for (var i = 0; i < cookies.length; ++i) {
           var a = cookies[i].split("=");
           if (a.length == 2) {
               a[0] = a[0].trim();
               a[1] = a[1].trim();
               if (a[0] == name) {
                   return unescape(a[1]);
               }
           }
       }
       return "";
   }
   

在页面增加一个 隐藏域
js代码里面直接去取 id为input的值

jsp中直接写java代码：
<%
String s = pageContext.request.getSession.getAttribute("xxxx");
%>
jsp页面获取session的值<%=s%>

js拿不到session...

AJAX ~~~~~~~~~~~~~~