angularjs中$http POST中文参数乱码

$http({
            method: "POST",
            url: "",
            data: id,
            headers: { 'Content-Type': 'application/x-www-form-urlencoded;charset=utf-8' },
            transformRequest: function(obj) {
                var params= [];
                for (var p in obj) {
                 //判断参数值是否存在，不存在赋空
                  if(!obj[p])
                         obj[p]='';
                    params.push(encodeURIComponent(p) + "=" + encodeURIComponent(obj[p]));
                }
                return params.join("&");
            }
        }).success();