When adding the module to an existing module that already has a POM, it is necessary to manually specify that the new module will be in a different directory. This is counter-intuitive, but I think the "Add Module" dialog was not built with maven specifically in mind.
What this means is when you are adding a module to an existing module with a POM, for example, an aggregator project, on the second page of the dialog, you need to manually copy and paste the "Module Name" onto the end of the "Content root" and "Module file locations".
在這個頁面把moudle的名字加上