Peter Ledbrook :

One ready-made implementation of the pattern for GWT is the gwt-dispatch library. I considered integrating this into the Grails plugin, but its server-side components weren’t really suitable for a Grails project. Anyway, I wanted to write something myself so I could better understand what the implementation should do. The result is the plugin’s new action framework, which you can test out with an intermediate release of the plugin.

The Command Pattern with the Grails GWT Plugin