how to specify relative path in jsp

hi all,

i want the client to download a file from server side

here is my directiory structure

                  WebRegistration
                          /        \
                         /          \
                        /            \
                      jsp           WEB-INF
                      /              \
                     /                \
                    /                  \
               localreg             classes
                                      /  
                                     /
                                 registration  
                                  /
                                 /
                              files

my jsp's are in left "localreg" folder  and my java programs are in "registration" folder and the file which client should download is in "files" folder

here is the jsp which i am using to make client download the file

String filename ="download.ash";(this is in "files"folder)
String filepath =
response.setContentType("APPLICATION/OCTET-STREAM");
response.setHeader("Content-Disposition","attachment; filename=\"" + filename + "\"");
out.flush();
java.io.FileInputStream fileInputStream =new java.io.FileInputStream(filepath+"/"+filename);
int i=0;
while ((i=fileInputStream.read())!= -1)
{
     out.write(i);
}
fileInputStream.close();
out.flush();
out.close();

what i want to know is how should i write "filepath"(in the porgram) relatively.

thanks in advance

regards,
vamshi