拦截$.ajax方法实现登录过期登录

 jQuery(function ($) {

    var CreateLoginWindows = function (callback) {
        var h = 300;
        $('#CreateLoginWindowsDlg').dialog({
             500,
            height: h,
            modal: true,
            title: "系统登录"
        });

        var urlStr = LoginWindowsPage;
        $('#CreateLoginWindowsDlg').empty();
        $('#CreateLoginWindowsDlg').append("<iframe style='98%;height:98%;border:0px;' src='" + urlStr + "'></iframe>");
        var top = $(document).scrollTop() + ($(window).height() - h) * 0.5;
        $('#CreateLoginWindowsDlg').window('open').window('resize', { top: top });
    };

    // 备份jquery的ajax方法    
    var _ajax = $.ajax;
    // 重写ajax方法，先判断登录在执行success函数   
    $.ajax = function (opt) {
        var _success = opt && opt.success || function (a, b) { };
        var _opt = $.extend(opt, {
            success: function (data, textStatus) {
                if (data.Message == "请重新登录") {//要求登陆
                    CreateLoginWindows();
                    return false;
                }
                _success(data, textStatus);
            }
        });
        _ajax(_opt);
    };
});