This is an old project develop using JSP, my plan was to inject some new element into this project. I got the error Can not find the tag library descriptor for http://java.sun.com/jsf/facelets when the following line was included in this JSP page:
< %@ taglib uri="http://java.sun.com/jsf/facelets" prefix="ui"% >
This is impossible because Facelets is to replace JSP, it is a XML based view technology which is designed to be a successor of JSP. If I do this, this is definitely a brainless move. No choice, in order to use Facelets, I must have XHTML but not JSP.