ajax同步页面假死解决方法

  $.when(AreaBWSet(urlStr,jsonSetting,settingType)).then(successFunc,failureFunc); 这段代码总是进不到then里，求大神指教。
     //向服务器端同步发送请求数据
        function AreaBWSet(urlStr,jsonSetting,settingType) {
            var defer = $.Deferred();
            $.ajax({
                type: "POST",
                url:urlStr,
                data:{"jsonSetting":jsonSetting,"settingType":settingType},
                success: function (data) {
                    defer.resolve(data);
                }
            });
            return defer.promise();
        }