public function __construct()
 {
     parent::__construct();
     $this->load->library(array('UserAuth', 'Http'));
     $this->load->model(['MLog']);
     $this->load->helper(array('api_filter_fields'));
     self::$_app_required_fields = C('app_filter_fields');
     $this->post = json_decode(file_get_contents("php://input"), TRUE);
     // 从post中json字符串中解析出变量并合并到$_POST
     if (!empty($this->post)) {
         $this->post = xss_clean($this->post);
         $_POST = array_merge($_POST, $this->post);
     } else {
         $this->post = xss_clean($_POST);
     }
     $this->_select_service_by_url();
     //过滤非法访问
     //$this->_check_sign();
     // 记录系统日志
     $this->MLog->record($this->userauth->current(TRUE));
     // 激活分析器以调试程序
     //$this->output->enable_profiler(TRUE);
 }