The App Engine sandbox imposes some restrictions. The most notable of these is that you cannot run background threads. Here’s how to make Wicket play ball:

• Make sure you’re running in deployment mode (this will disable the background thread that checks for modifications to your resource files, and is what you’ll want for deploying to a remote site like this anyway).
• Override newSessionStore() in your WebApplication subclass and return a new HttpSessionStore(this). (The default DiskPageStore uses a background thread and writes files, neither of which are supported in the App Engine’s sandbox.)
• Enable session support in appengine-web.xml.

App Engine for Java is in limited beta, but if you’ve been to the London Wicket Users Group at Google and would like me to wangle an account for you, please e-mail me (details on the About page).

We’re pleased to have Ari Zilka (who founded Terracotta) coming along. He will be giving a talk, as will Richard Wilkinson, who has interesting things to say about integrating Wicket with Guice and JPA. There will be a couple of other talks and some nice demos, too. If you’re wondering what it’s like to write real code in Wicket, don’t miss it.

If you’d like to come along, please wander over to the jWeekend site to sign up.

Becoming an Apache project, with all the benefits that brings, has not gone unnoticed by the wider Java development community. Particularly within the enterprise, the Apache brand (and ASF license) seems to bring with it a promise of professionalism and confidence. A bunch of banks and corporates now list it on their job advertisements, including the likes of Nokia and Time Warner. Despite the explosion in attention, the signal-to-noise ratio on the mailing lists remains impressively high. People are being really helpful both there and also with bug reports and patches, so a big thank you from all us Wicket developers to all you folk out there in the community who are making this growth in interest both workable and sustainable.

Talking of explosions, there has been a staggering level of interest in community meet-ups. When Cemal and I founded the London Wicket User Group a few months back (next meeting Dec 5th) we both hoped the concept would take off elsewhere, so we’re happy to see the vast number of other groups forming across the globe, in a quite astonishing number of places: Antwerp, Amsterdam, Copenhagen, London, Minneapolis, Rio de Janeiro, Seattle, San Francisco, Stockholm, and also somewhere TBC in Austria. I’m surprised there’s not one in New York City yet. Come on guys! ;-)

The Amsterdam meet-up on November the 30th is looking particularly awesome (80 people registered interest, which will probably equate to 50+ people). The level of Wicket expertise gathered in one room will be unprecedented – get yourself along if you possibly can.

For more information, check out the wiki page: Apache Wicket community meet-ups.

Go Wicket!

• How many tools (i.e. IDE plugins) are available for your web framework?
• How many jobs are available for your framework on Dice.com? What about Indeed.com?
• How many messages where [sic] posted to your user mailing list (or forum) in March 2007?
• How many books are available for your framework?

What on earth does he intend to do with them, I wonder? All of these numbers superficially look like they should be “more is better”. On second glance, they’re anything but:

• If you have lots of IDE tooling available, it probably means the configuration for the framework is overly complex and unmanageable without it.
• The framework with the largest number of jobs available is probably Struts 1. Enough said.
• People only post to user lists when they are stuck. If the framework is hard to use, there will be lots of e-mails. If it has a steep learning curve, and/or the documentation is poor, this will be particularly so. On the other hand, an active list might point to a large active user base. Who knows which is which from a raw figure? It might be better to find the number of posters, not the number of messages.
• If your framework is fairly stable, and someone has written a fabulous tome on it that is universally acknowledged as “the bible”, few people would bother writing another book for it. Niche books usually only get written if there is no book currently in that space or if the existing books are rubbish and the author(s) think they can do better. How many books are written is therefore a function of the number written on the subject before a good one arrives, and how stable your framework is. The first is a small random number, probably. The second number is “more is worse”, assuming you don’t like frameworks that change under you all the time.

So, I guess I’m curious what extrapolations Matt intends to make from these figures. ;-)

Things I noticed:

• People think Second Life is cool, but no one knows what to do with it yet.
• People work on open source in their spare time. It had better be fun. Most of the under 30s were working on Python or RoR-based projects; the Java coders jumped up and down a bit less and had deeper voices. ;-)
• Django is generating buzz. Either that, or they came in a big group for fear of the Rails folk eating them.
• Quite a few people are finding AJAX UI-design hard. It’s difficult to adhere to the principle of least surprise, when you’re building stuff the like of which no-one’s seen on the web before.