public function __construct($id, $module, $config = array())
{
parent::__construct($id, $module, $config);
/** set default output format to json */
$_format = Yii::$app->getRequest()->getBodyParam('_format');
if (empty($_format)) {
Yii::$app->getRequest()->setQueryParams(['_format' => Response::FORMAT_JSON]);
}
}
