Here's my understanding of the various environmental variables that can be passed with a request, and exactly how they relate to the actual URL:
if set, then the URL should be constructed by joining DOCUMENT_ROOT and REQUEST_URI (without query string, of course)
points to the adapter portion of the URL (after rewrite)
the rest of the path after the adapter (after rewrite)
the original URL requested (pre-rewrite ?)
the file the original URL would have pointed to (?) -- or maybe just a different name for SCRIPT_NAME
the path of the original (pre-rewrite) request
the full URI (with hostname) of the original (pre-rewrite) request
Information produced from this:
the context of the request
the servlet it points to
the extra portion of the URL
the url of the adapter
the hostname
the url of the servlet, with adapter and context
the url of the servlet, with extraPathInfo as well
the url of the adapter
the url of the context
-- IanBicking - 26 Jun 2002