When selecting on of the choices of the autocomplete field per mouse click the onchange event fires twice.
The first onchange event is fired by the browser in response to the mouseclick. The second one is fired by the autocomplete.js.
If you hook an onchange event listener to the ac (as in the wicket example) field it gets called twice per selection. The first time the text entered by the user
gets submitted. The second time the selected choice is submitted.