How can I control the name of the top directory of the maven module created by my maven archetype? Currently it creates a new folder named$artifactId. Or even more directly, is there a way that my archetype can create a folder named after the module's artifactId, but with dashes replaced by underscores?
The naming convention for artifactId's is to use dashes (hyphens). I don't think there is any way to make the module's directory named something other than the artifactId. That being said, it is onlvy convention, not a requirement, that your module be named the same as your artifactId. This means that after your project is generated, you could simply change either the artifactId or module folder name or both to whatever you want.