public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest httprequest = (HttpServletRequest) request;
HttpServletResponse httpresponse = (HttpServletResponse) response;
String url = httprequest.getRequestURL().toString();
if (httprequest.getSession()== null) {
if (httprequest.getHeader("x-requested-with") != null
&& httprequest.getHeader("x-requested-with").equals(
"XMLHttpRequest")) { // ajax请求
httpresponse.setHeader("sessionstatus", "timeout");
} else {
httpresponse.sendRedirect("/test/index.jsp");
return;
}
} else {
chain.doFilter(request, response);
}
}
这样，如果session超时，而且是ajax请求，就会在响应头里，sessionstatus有一个timeout；
再用一个全局的方法来处理，session超时要跳转的页面。
jquery 可以用$.ajaxSetup 方法，ext也有类似的方法:
//全局的ajax访问，处理ajax清求时sesion超时
$.ajaxSetup({
contentType : "application/x-www-form-urlencoded;charset=utf-8",
complete : function(XMLHttpRequest, textStatus) {
var sessionstatus = XMLHttpRequest.getResponseHeader("sessionstatus"); // 通过XMLHttpRequest取得响应头，sessionstatus，
if (sessionstatus == "timeout") {
// 如果超时就处理 ，指定要跳转的页面
window.location.replace("/test/index.jsp");
}
}
});