I am trying to learn Grails along with the Spring Security plugin. I am using Grails 2.3.0 with springsecurity-RC2 plugin and following the guide on the Grails website.
This is by design. The files aren't generated anymore, they're included in the plugin itself. If you need to modify them, copy the controller and/or GSPs to your project in the same location under grails-app and make your changes there. Apps can always override plugin classes using this approach since Grails compiles plugins first, then the app.