For the method "getRequestDispatcher() "
we have to give the arguement as the physical path (starts with context root /)
for the method getnamedDispatcher()
its enough to give the
servlet name(<servlet-name> in the web.xml) as the arguemnt(This is because you can dispatch ypur request to the servlet which has no public access that means the servlt may not have the <servlet-mapping> in the web.xml file)