Extending Confluence using Wicket

Recently I started to work at two projects in my new job, in one of them doing some plugins to Atlassian Confluence (which is a yet-another-java-based-wiki) and participating on another that uses wicket.

In order to add new (visual) functionality to confluence, it’s common to use XWork to create new actions or replacing the existent actions to add new behavior. I particularly don’t like Xwork and in one of the moments to avoid boredom in these two projects I decided to somehow try to do wicket development inside confluence. The advantage would be avoiding completely XWork, possibility to use wicket advanced features and possibility to run the feature outside confluence (more testable).

So I started giving a look at the Confluence PDK (Plug in development kit), and see that it was already possible to define a servlet as part of a plugin

I then started declaring the wicket servet in atlassian-plugin.xml:

And creating the WicketApplication that simply loads my page:

That will use the Confluence API in order to do a paginated ajax table with the names of the plugins available on confluence.

After that, confluence will load the servlet and will make it available on the /plugins/servlet/sampleplugin/  URL.


1. The first problem is that the output will be strictly the page output, without confluence headers and menus. There’s an issue describing that bug, but while it is not fixed commenting the line 16 in the WEB-INF/decorators.xml in your confluence installation will suffice:


That line when uncommented tells that for the URLs starting with “/plugins”, no decorator will be used. So, It’s enough to comment it.

2. The second problem is that confluence does not destroys the servlet when the plugin is uninstalled using maven PDK tool. There is another issue describing that problem. Basically, wicket creates its session object using one classloader. When the plugin is removed and reinstalled, it’ll gain another classloader. So nasty ClassCastExcetions occurs on trying to obtain the wicket session. The workaround for now is to restart the server on reinstall of the plugin.

Here we can see the final result: The standard confluence header and footer, and the wicket page in the center.

Download here the zip file containing the maven project for this example plugin.