The relative path concept varies from context to context.
Whenever you are talking about File, the path is relative to the current directory from where you are running the web-server. Like, if you run the
tomcat from c:\tomcat\bin and try to use new File("abc.jar"), you must place the "abc.jar" file in "c:\tomcat\bin".
But, in case of any response.sendRidirect(), the relative path is as you specified.