Gets any optional extra path information following the servlet
path of this request's URI, but immediately preceding its query
string, and translates it to a real path.
Applies alias rules to the specified virtual path and returns
the corresponding real path, or null if the translation can not
be performed for any reason.
Gets the current valid session associated with this request, if
create is false or, if necessary, creates a new session for the
request, if create is true.