Organization External and Internal pages ( with login)

Hi , I am trying to create a 14+ Spring Application with Public and Private Pages , where public pages are open and can be accessed by anyone and no login access should be prompted, but private pages requires a Login prompt.
This way , if some one access ,public pages should be visible and accessible with no login prompt,
but , should show the login page.

Is it possible , if so how can i achieve it ?

Let me try to rephrase the question. How can I call on-demand vaadin login page. This way user can login for certain pages.