doc root problem - help

hi,
i am moving changing a web server from java web server to jigsaw. one of
the servlets that i have to port has the getRealPath() function of the
ServerRequestClass bu the result is null. if i give "/" as the parameter
of the above stated function i get a null value. but in case of the java
web server i get the following as the doc root:
"c:\javawebserver1.1\bin\..\public_html" .

how  do i get over this problem please help it is real urgent..

TAI,
anshuman