adding url parameters to grails form

adding url parameters to grails form

I have a form and want to add customer URL parameters , for example in the
classical "create"
http://localhost:8080/test/customer/create?abc=asd
I changed the form from POST to GET, both in the view file method="GET"
and in the controller, remove the allowedMethods
Still the custom parameter "abc" is not inserted from the view to the
action, it does not appear in the params - params.abc is null
the show action works
http://localhost:8080/grails/copyOfLead/show/3?abc=asd
works....