Yes, it *is* in fact possible to have clean, well-designed, query-parameter free URIs with JSP.
Expose the public URI:
/tag/foo/
Then you can use Apache to re-write it to:
/index.jsp?tag=foo
With the following directives:
RewriteEngine on
RewriteRule ^/tag/([^/]*)/ /index.jsp?tag=$1 [PT]