8.3 URL Mappings
Throughout the documentation so far the convention used for URLs has been the default of /controller/action/id. However, this convention is not hard wired into Grails and is in fact controlled by a URL Mappings class located at grails-app/controllers/mypackage/UrlMappings.groovy.
The UrlMappings class contains a single property called mappings that has been assigned a block of code:
package mypackageclass UrlMappings {static mappings = {}}