Javadoc
Create the content for the login form with the supplied user name field,
password field and the login button. You cannot use any other text fields
or buttons for this purpose. To replace these components with your own
implementations, override
#createUsernameField(),
#createPasswordField() and
#createLoginButton(). If you
only want to change the default captions, override
#getUsernameCaption(),
#getPasswordCaption() and
#getLoginButtonCaption(). You do not have to use the login button
in your layout.