freeze the application

hiii every body…
i am developing the application using vaadin and i have a requirement like…
while using the application if user need to freeze the application for that he clicks the button then the application has to be freeze than
when he came came when he clicks the window it has to ask the password like that any addon is there or any sample code… or any suggestions

Just open a modal dialog with your main-window as parent, displaying the password-field. Set it closable = false so that it can only be closed after entering a valid password.

That should work against casual passers-by but might not block someone who knows how to craft and send requests by hand from the browser - they might be able to interact with components that are visible behind the modality curtain. Those components can also be seen on the browser, either directly or using browser debug tools.

If you need stronger security and/or hiding the visible components, first replace the main layout of the top-level (browser) window with an empty one using setContent(newLayout) and then show the modal dialog. Keep a reference to the old layout somewhere so you can switch back to it when the correct password is entered.