public function execute(HTTPRequest $request, callable $callback, $flush = false)
    {
        try {
            return $this->callMiddleware($request, function ($request) use ($callback, $flush) {
                // Pre-request boot
                $this->getKernel()->boot($flush);
                return call_user_func($callback, $request);
            });
        } catch (HTTPResponse_Exception $ex) {
            return $ex->getResponse();
        } finally {
            $this->getKernel()->shutdown();
        }
    }