I have pulled out half my hair trying to get this working with Java and I'm about a stone throw away from it finally working. If anyone wishes to create a Java client for the Wikidot API, I'd gladly help you as much as I can. I nearly gave up several times.
I'll eventually be making a Java library for the Wikidot API, so that access to it using Java is really simple. It'll fully support object-oriented development, allowing you to access specific information about users, sites, categories and pages - and will be updated every time the API itself is updated.
(shameless plug) If you'd like to have a look at my wikidot editor, it will soon have API access added to its list of features. http://editor.wikidot.com
~ Shane (Wikidot Community Admin - Volunteer)
Wikidot: Wikidot Editor, Official Docs
Other: YouTube (gaming, primarily Minecraft)