Not sure whether this is too late to post.
In Tomcat ,you might get 404 error for your jsp file if it is inside WEB-INF directory and in web.xml you have not mentioned file path from WEB-INF.
Like in web.xml it should be written as :
<welcome-file>/WEB-INF/index.jsp</welcome-file>
This is a security reason.
Hope it helps.
-Shruti