Portlets and handleRenderRequest

Vaadin 6 / 7 / 8
1

I’m a little bit confused about using Vaadin 7 and portlets: I have a lot of portlets working well with liferay 6.1 and vaadin 6.
Now I would like to upgrade all my portlets and the portal to Vaadin 7.

To migrate portlets I use the PortletListener (even if VaadinPortletSession is deprecated)

if (VaadinSession.getCurrent() instanceof VaadinPortletSession) {
            VaadinPortletSession portletsession = (VaadinPortletSession) VaadinSession.getCurrent();

            // Add a custom listener to handle action and
            // render requests.
            portletsession.addPortletListener(this);
        }

but Render request is called only after a refresh of the page.
I understand that the init method is called the first time and tells the application to add portlet behaviors;
after this, all other refresh will call the handleRenderRequest.

Is it normal? Am I missing something?
And why is VaadinPortletSession deprecated?

Thanks.
Antonio