What is the easiest way to do background loading in Wicket?

Question

I have a simple Wicket form that allows users to select some data and then upload a zip file (generated on the fly) containing what they ask. Currently, the form method onSubmit()looks something like this:

public void onSubmit() {
    IResourceStream stream = /* assemble the data they asked for ... */ ;
    ResourceStreamRequestTarget target = new ResourceStreamRequestTarget(stream);
    target.setFileName("download.zip");
    RequestCycle.get().setRequestTarget(target);
}

This works, but of course the request stops there and it is not possible to display any other feedback for the user.

What I would like to have is something like a typical "Your requested [NAME] download should start automatically. If not, click this link." Ideally, the same page is still displayed, so the user can immediately select some other data and load it.

I assume that this can be done using the Wicket Ajax classes, but I managed to avoid using them so far, and it does not immediately seem to me right away. What is my fastest way out here?

---

Updated for the answer from Zeratul, below: I got something like this:

class MyDownloader extends AbstractAjaxBehavior {

    private final MyForm form;

    MyDownloader(MyForm form) {
        this.form = form;
    }

    void startDownload(AjaxRequestTarget target) {
        target.addComponent(myForm);
        target.appendJavascript("window.location.href='" + getCallbackUrl() + "'");
    }

    @Override
    public void onRequest() {
        try {
            ResourceStreamRequestTarget streamTarget = form.getStreamTarget();
            form.info(/* some status message */);
            getComponent().getRequestCycle().setRequestTarget(streamTarget);
        catch (SomeException e) {
            form.error(e.getMessage());
        }
    }
}

class MyForm extends Form {

    private final MyDownloader myDownloader;
    private final Object myModel;

    MyForm(Object aModel) {
        super("myForm");
        myModel = aModel;
        myDownloader = new MyDownloader(this);

        add(myDownloader);

        add(/* form components */);
        add(new AjaxButton("download", new Model<String>("Download"), this) {
            @Override
            protected void onSubmit(AjaxRequestTarget target, Form<?> form) {
                myDownloader.startDownload(target);
            }
        });

        add(new FeedbackPanel("feedback"));
    }

    ResourceStreamRequestTarget getStreamTarget() throws SomeException {
        return /* target based on form input */;
    }
}

This is a little annoying, but it seems to work.

Answer 1

This article has an article about Apache clicks, it might suit you:

download ajax