Vaadin Push not work,an obvious BUG？

Server push (long polling)In my application does not work .I use the official vaddin-spring add-on ,and my app is based on springBoot.
After deeply debuging vaadin's code,I  found the bug:

Vaadin framework integrates Atmosphere Framework to support push ,when the vaadin UI is inited ,the client  will send a push request to the server:

http://localhost:8080/deeryo/vaadinServlet/PUSH?v-uiId=1&v-csrfToken=395f908b-73ad-44b9-8995-18678deb9cc1&X-Atmosphere-tracking-id=0&X-Atmosphere-Framework=2.2.13.vaadin3-jquery&X-Atmosphere-Transport=long-polling&
X-Atmosphere-TrackMessageSize=true&Content-Type=application%2Fjson%3B%20charset%3DUTF-8&X-atmo-protocol=true&_=1468289101510

but  Atmosphere Framework  determine the PushMode from reqeust header ,but not  from the request query parameter.the code is:
AtmosphereResourceImpl.java

private TRANSPORT configureTransport() {

        if (req == null) return UNDEFINED;

        String s = req.getHeader(HeaderConfig.X_ATMOSPHERE_TRANSPORT);

        if (s == null) return UNDEFINED;
        if (s.equals(UNDEFINED.name()) && Utils.rawWebSocket(req)) {

            return TRANSPORT.WEBSOCKET;

        }

        s = s.replace("-", "_").toUpperCase();

        if (TRANSPORT.POLLING.name().equals(s)) {

            return TRANSPORT.POLLING;

        } else if (TRANSPORT.LONG_POLLING.name().equals(s)) {

            return TRANSPORT.LONG_POLLING;

        } else if (TRANSPORT.STREAMING.name().equals(s)) {

            return TRANSPORT.STREAMING;

        } else if (TRANSPORT.JSONP.name().equals(s)) {

            return TRANSPORT.JSONP;

        } else if (TRANSPORT.WEBSOCKET.name().equals(s)) {

            return TRANSPORT.WEBSOCKET;

        } else if (TRANSPORT.SSE.name().equals(s)) {

            return TRANSPORT.SSE;

        } else if (TRANSPORT.AJAX.name().equals(s)) {

            return TRANSPORT.AJAX;

        } else if (TRANSPORT.CLOSE.name().equals(s)) {

            return TRANSPORT.CLOSE;

        } else {

            return UNDEFINED;

        }

    }

as a result, the transport  is UNDEFINDE !!! So,my push(long-polling) can't work.