new ShortTextField("address.street", "Street"),
new ShortTextField("address.city", "City"),
new ShortTextField("address.country", "Country")
);
SimpleFormLayout layout = new SimpleFormLayout();
layout.addGroup(new FieldGroup("Contact Details").setOptional(true).setKeys(
"address.street", "address.city", "address.country"
));
final FormPanel formPanel = new FormPanel(form, layout);