Robert,
Also please note that task handler connects to the task service using a lazy connection approach.
You, however, can connect immediately so that you retrieve the task completion events even before the first task is created. To instantiate the listener using this approach you might modifying your code like this:
CommandBasedWSHumanTaskHandler taskHandler = new CommandBasedWSHumanTaskHandler(ksession);
ksession.getWorkItemManager().registerWorkItemHandler("Human Task",taskHandler);
taskHandler.connect();