Do welcome files need to exist?
The welcome file mechanism allows a request to /some/directory/ to be
served by the contents of a file like /some/directory/index.html.
If there is a servlet mapped to handle the welcome file, it will be called.
So if index.jsp is configured as a welcome file, then a request to /some/directory/
will be passed to the JspServlet mapped at *.jsp to handle the /some/directory/index.jsp file.
However, the file MUST exist for the welcome file mechanism to work. Even if index.do is defined as a welcome file, then a request to /some/directory/ will
not be passed to a servlet handling .do for some/directory/index.do *UNLESS THE FILE EXISTS.
If you want an index to be served by a servlet, then I suggest you use a filter
to do the redirection. See the WelcomeFilter.java for an example.