Java.net has a good article about Log4Ajax. As someone who has experienced the pain surrounding building an AJAX enabled application and debugging with alert statements I think this is a good resource. It looks as though this tool can write logging statements to the Browser or back to the server. Sweet!

I've been using the JavaScript set of libraries called MochiKit. It has the same ability to write generic logging statements to the browser window as well. However, with Log4Ajax having the added ability to log to the server side I might start using it instead.

The author Eric Spiegelberg describes the article as follows:

As you have undoubtedly heard, the latest and greatest four-letter acronym in the web-based software development world is AJAX. Despite the tidal wave of excitement and hype, there is another four-letter word that can be associated with AJAX: pain. The dirty little secret is that there are many reasons developing AJAX applications can hurt. Some of these reasons are the browsers' fault, due to the fact that each browser version offers differing levels of DOM and JavaScript compliance.

If you've written JavaScript, especially if it's just an aside to your primary Java development, you know what a pain it can be to make the mental switch to the familiar-enough-to-bite-you-in-the-ass JavaScript syntax. Worse is that when you try to debug your script, you don't have a sophisticated logging framework, or even stdout to fall back on. The typical response is to use alert() as a de facto System.out.println(), but clicking through one alert after another, run after run, is inefficient and tiresome.

In today's Feature Article, Eric Spiegelberg has an alternative: Log4Ajax shows how to write a client-side logging library that can log debugging messages, of varying levels of verbosity, to a