Modal Window under Vaadin 7

Hello,

I would like to create a modal Dialog/Window within a
Vaadin 7
UI -class.
Also and particularly would I like to close this modal dialog… of course within the same
Vaadin 7
UI -class.

I do know how to implement that under Vaadin 6. But honestly, the migration guide didn’t really help to find it out.

Thank you in advance for any help (source code)