required field validation in grails

Question

Hi I am a newbie to grails and would like to know how I can set a required field validation on grails gsp or controller.for Eaxmple , if the user doest enter the user name then I should promt a message saying user name is required.

Thanks sam

Answer 1

The user manual discusses this extensively. See http://grails.org/doc/latest/guide/7.%20Validation.html

Answer 2

Lookup Command objects: http://www.grails.org/Command+objects+and+Form+Validation

class MyController {

    def myAction = { MyCommand cmd ->
        if (cmd.hasErrors()) {
            // do fail things
        }
        else {
            // do success things
        }
    }

}

class MyCommand {
    String username

    static constraints = {
        username(nullable:false, blank:false, minSize:4)
    }
}