src/Web/ResponseBuilder.php
protected function defaultFormatters()
    {
        return [
            Response::FORMAT_HTML => [
                'class' => 'Reaction\Web\Formatters\HtmlResponseFormatter',
            ],
            Response::FORMAT_XML => [
                'class' => 'Reaction\Web\Formatters\XmlResponseFormatter',
            ],
            Response::FORMAT_JSON => [
                'class' => 'Reaction\Web\Formatters\JsonResponseFormatter',
            ],
            Response::FORMAT_JSONP => [
                'class' => 'Reaction\Web\Formatters\JsonResponseFormatter',
                'useJsonp' => true,
            ],
        ];
    }
protected function defaultFormatters()
    {
        return [
            Response::FORMAT_HTML => [
                'class' => 'Reaction\Web\Formatters\HtmlResponseFormatter',
            ],
            Response::FORMAT_XML => [
                'class' => 'Reaction\Web\Formatters\XmlResponseFormatter',
            ],
            Response::FORMAT_JSON => [
                'class' => 'Reaction\Web\Formatters\JsonResponseFormatter',
            ],
            Response::FORMAT_JSONP => [
                'class' => 'Reaction\Web\Formatters\JsonResponseFormatter',
                'useJsonp' => true,
            ],
        ];
    }
Get default formatters
@return array the formatters that are supported by default