ServletContext.getRequestDispatcher
http://download.oracle.com/javaee/5/...lang.String%29 Cita: Use getContext to obtain a RequestDispatcher for resources in foreign contexts. This method returns null if the ServletContext cannot return a RequestDispatcher.
ServletRequest.getRequestDispatcher
http://download.oracle.com/javaee/5/...lang.String%29 Cita: The difference between this method and ServletContext.getRequestDispatcher(java.lang.Stri ng) is that this method can take a relative path.
Tu usas una ruta relativa, por lo tanto ServletRequest.getRequestDispatcher