ExpressionManager expressionManager = context.getExpressionManager();
// create decorator
TaskDecorator taskDecorator = new TaskDecorator(taskDefinition, expressionManager);
// set taskDecorator on behavior
HumanTaskActivityBehavior behavior = (HumanTaskActivityBehavior) activity.getActivityBehavior();
behavior.setTaskDecorator(taskDecorator);
// task listeners
initializeTaskListeners(element, activity, context, taskDefinition);
}