Wicket retrieve javascript variable to use in java

Question

I am trying to retrieve a javascript variable using Java. I think that I am close to the solution.

I want to retrieve the width of an element on my panel. To achieve this, I added a behavior to my panel that adds the callback and retrieves the parameters (width and height).

private class ImageBehavior extends AbstractDefaultAjaxBehavior {

    @Override
    protected void respond(AjaxRequestTarget target) {
        //I receive a JavaScript call :)
        StringValue width  = getRequest().getRequestParameters().getParameterValue("width");
        StringValue height = getRequest().getRequestParameters().getParameterValue("height");       
    }

    @Override
    protected void updateAjaxAttributes(AjaxRequestAttributes attributes) {
        super.updateAjaxAttributes(attributes);
        attributes.getExtraParameters().put("width", "undef");
        attributes.getExtraParameters().put("height", "undef");
    }

    @Override
    public void renderHead(Component component, IHeaderResponse response) {
        super.renderHead(component, response);
        response.render(OnDomReadyHeaderItem.forScript(getCallbackScript().toString()));

    }
}

In javascript, the following code gets called:

function callbackWicketNewImage(element) {
    var wcall = Wicket.Ajax.get({ 'u': 'callbackUrl', 'ep' : {'width': element.width(), 'height': element.height()}});
}

When the js-code is called, the 'respond' method gets called but the values of the width and height parameter did not change. They remained 'undef'.

Answer 1

I fixed my problem with the following code. Please note that the abstract onResponse method is for abstraction purposes.

public abstract class SizeBehavior extends AbstractDefaultAjaxBehavior {

@Override
protected void respond(AjaxRequestTarget target) {
    IRequestParameters request = RequestCycle.get().getRequest().getRequestParameters();
    onResponse(request.getParameterValue("widthParam").toDouble(),
            request.getParameterValue("heightParam").toDouble());
}

@Override
protected void updateAjaxAttributes(AjaxRequestAttributes attributes) {
    super.updateAjaxAttributes(attributes);
    attributes.getDynamicExtraParameters()
    .add("return {'widthParam': $(" + getComponent().getMarkupId() + ").width(), " +
                 "'heightParam': $(" + getComponent().getMarkupId() + ").height()}");
}

public void renderHead(Component component, IHeaderResponse response) {
    response.render(OnLoadHeaderItem.forScript(getCallbackScript().toString()));
}

public abstract void onResponse(double width, double height);
}  

Behavior call:

add(new SizeBehavior() {
    @Override
    public void onResponse(double width, double height) {
        //set vars..
        widthVar = width;
        heightVar = height;
    }
});