import com.vaadin.shared.ui.ui.Transport; //导入依赖的package包/类
/**
 * Configuration du push
 */
private void configPush() {		
	if (pushTransportMode!=null && pushTransportMode.equals(Transport.LONG_POLLING.getIdentifier())){
		getPushConfiguration().setTransport(Transport.LONG_POLLING);
	}else if (pushTransportMode!=null && pushTransportMode.equals(Transport.WEBSOCKET_XHR.getIdentifier())){
		getPushConfiguration().setTransport(Transport.WEBSOCKET_XHR);
	}else{
		getPushConfiguration().setTransport(Transport.WEBSOCKET);
	}
}
 

import com.vaadin.shared.ui.ui.Transport; //导入依赖的package包/类
@Override
public Transport getPushTransport(UICreateEvent event) {
    WebConfig webConfig = configuration.getConfig(WebConfig.class);

    if (webConfig.getUsePushLongPolling()) {
        return Transport.LONG_POLLING;
    }

    return super.getPushTransport(event);
}
 

import com.vaadin.shared.ui.ui.Transport; //导入依赖的package包/类
/**
 * Clears the session of all attributes except some internal Vaadin attributes and reinitializes it. If Websocket
 * Push is used, the session will never be reinitialized since this throws errors on at least
 * Tomcat 8.
 */
protected void clearAndReinitializeSession() {
    final VaadinRequest currentRequest = VaadinService.getCurrentRequest();
    final UI currentUI = UI.getCurrent();
    if (currentUI != null) {
        final Transport transport = currentUI.getPushConfiguration().getTransport();
        if (Transport.WEBSOCKET.equals(transport) || Transport.WEBSOCKET_XHR.equals(transport)) {
            LOGGER.warn(
                "Clearing and reinitializing the session is currently not supported when using Websocket Push.");
            return;
        }
    }
    if (currentRequest != null) {
        LOGGER.debug("Clearing the session");
        final WrappedSession session = currentRequest.getWrappedSession();
        final String serviceName = VaadinService.getCurrent().getServiceName();
        final Set<String> attributesToSpare = new HashSet<String>();
        attributesToSpare.add(serviceName + ".lock");
        attributesToSpare.add(VaadinSession.class.getName() + "." + serviceName);
        for (String s : currentRequest.getWrappedSession().getAttributeNames()) {
            if (!attributesToSpare.contains(s)) {
                LOGGER.trace("Removing attribute {} from session", s);
                session.removeAttribute(s);
            }
        }
        LOGGER.debug("Reinitializing the session {}", session.getId());
        VaadinService.reinitializeSession(currentRequest);
        LOGGER.debug("Session reinitialized, new ID is {}",
            VaadinService.getCurrentRequest().getWrappedSession().getId());
    } else {
        LOGGER
            .warn("No VaadinRequest bound to current thread, could NOT clear/reinitialize the session after login");
    }
}