Wicket quick tip #4: Change default AjaxChannel to Active

The default behavior provided in Wicket is too queue AJAX requests as they come in. Let’s say you have a button with a callback that does some work when clicked and updates the UI. This means that if the button is quickly clicked three times successively, the last two requests will be queued up and processed after the first request finishes.

The problem

This may be okay but there are some situations when this type of behavior is not desirable. I came across this situation when debugging hard to reproduce bugs. I found other people asking about this same problem.

This often becomes a problem when impatient users double or triple click buttons and links that do some work on the server-side and potentially update the UI. The problems are exacerbated when the internet connection speed is slow.

Solution

A simple solution is to change the behavior of the AjaxChannel from queueing to active. This means that if any AJAX requests are received while there is an active(unfinished) request being processed, they will be ignored.

So how do we override Wicket’s default behavior in one spot and ensure all AjaxChannel‘s are modified? We use a custom AjaxRequestTarget.IListener.

public class ActiveAjaxListener implements AjaxRequestTarget.IListener {
    
    private static final AjaxChannel ACTIVE_CHANNEL = new AjaxChannel(AjaxChannel.DEFAULT_NAME, AjaxChannel.Type.ACTIVE);

    @Override
    public void updateAjaxAttributes(AbstractDefaultAjaxBehavior behavior, AjaxRequestAttributes attributes) {
        attributes.setChannel(ACTIVE_CHANNEL);
    }
}

Our ActiveAjaxListener class will modify every AJAX behavior and make sure it uses the active channel. To register it, we simple insert this line into our WebApplication init() method:

getAjaxRequestTargetListeners().add(new ActiveAjaxListener());