 <p>I never got this to work under Grails 2.1.1, but apparently this was fixed in <a href="http://grails.org/doc/2.3.x/guide/introduction.html#whatsNew23" rel="nofollow">Grails 2.3</a>,</p> <blockquote> <p>Binding Request Body To Command Objects If a request is made to a controller action which accepts a command object and the request includes a body, the body will be parsed and used to do data binding to the command object. This simplifies use cases where a request includes a JSON or XML body (for example) that can be bound to a command object. See the Command Objects documentation for more details.</p> </blockquote>