Some containers allow it and some don't.
One trick that will almost always get it to work is to:
Add the entry to your welcome-file-list, as you already have done.Make sure you have a valid mapping for that entry.Create a blank file with the same name as the entry in your welcome-file-list. This way, when a request comes in, the welcome file mechanism will forward to the file you created but the
servlet mapping will cause the request to go to your servlet [action] instead.