I want to be sure that an action occurs always after page loading.
I dont't want to put a method call in the constructor, which other posibilities exists? For now the user must call the method explicitly with a button.
you could use a TIMER component - and specify via expression e.g. duration "1"... in the action listener of the timer you should immediately re-set duration of the timer to "0" so that the timer is only called one time.
I am not yet sure, why you want the user interface directly to connect back to the server, but I am sure there is a good reason ;-). If it is any initialization you want/might have to do: this should be better done before sending the new page to the client...