Wicket: run JavaScript when a Form is submitted

I'm using Wicket 6.xx and I have a Wicket Form that I use to upload some files. This is not a problem. The problem is that I need to run some JavaScript on the page after the form has been submitted in order to show a modal popup that is JavaScript based.

However, I can't do that because I don't have an AjaxRequestTarget object, since a form submission is not an Ajax call. Or at least, I'm guessing that's the reason. I've tried the following, taken from another thread, but it doesn't work:

From<RequestInfo> uploadFrm = new Form<RequestInfo>("uploadFrm", getModel()) {
    private static final long serialVersionUID = 1L;

    @Override
    protected void onSubmit() {
        AjaxRequestTarget target = RequestCycle.get().find(AjaxRequestTarget.class);
        target.appendJavascript("..."); //NullPointerException: target is always null
    }
};

As you can tell from the comment I put there, target is always null.

What is the proper way to run some JavaScript in a situation like this? Is there a proper way?

I think the best way to do that is to add an AjaxSubmitLink to your form so you can call javascript code inside the onSubmit method:

HTML code:

<form wicket:id="uploadFrm">
    <input type="submit" wicket:id="ajaxSubmitLink" value="OK" />
</form>

JAVA code:

Form<RequestInfo> uploadFrm = new Form<RequestInfo>("uploadFrm", getModel());   
AjaxSubmitLink ajaxSubmitLink = new AjaxSubmitLink("ajaxSubmitLink", uploadFrm) {
            @Override
            protected void onSubmit(AjaxRequestTarget target, Form<?> form) {
               target.appendJavaScript("you javascript");                          
            }

        };

        uploadFrm.add(ajaxSubmitLink);