public FormPanelSample() {
Form form = new Form();
form.addFields(
new ShortTextField("firstName", "First Name"),
new ShortTextField("lastName", "Last Name"),
new IntegerField("age", "Age"),
new ShortTextField("email", "Email").setValidators(Validators.email()),
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"