验证 grails 域 object 中的一组字段

Question

I have a command object that captures a feedback form with 3 textareas.

class FeedbackCommand {
    String textarea1
    String textarea2
    String textarea3
    String username 

    static constraints = {
        textarea1(nullable:true, blank:true)            
        textarea2(nullable:true, blank:true)            
        textarea3(nullable:true, blank:true)            
        username(nullable:false, blank:false)
    }
}    

I'd like to ensure that at least ONE of the textareas is filled out.

I came up with adding a fake flag field as a 'constraint' field, and then doing a bunch of object checks in the custom validator for that field. If after looking around in myself and i dont find what I want, I throw an error.

Right now, I'm doing this:

class FeedbackCommand {
    String textarea1
    String textarea2
    String textarea3
    boolean atLeastOne = true
    String username 

    static constraints = {
        textarea1(nullable:true, blank:true)            
        textarea2(nullable:true, blank:true)            
        textarea3(nullable:true, blank:true) 
        atLeastOne(validator: { boolean b, FeedbackCommand form, Errors err ->
          if (b) {
            if ( (form.textarea1==null || form.textarea1?.isAllWhitespace()) &&
                 (form.textarea2==null || form.textarea2?.isAllWhitespace()) &&
                 (form.textarea3==null || form.textarea3?.isAllWhitespace()))
            {
                // They havent provided ANY feedback. Throw an error
                err.rejectValue("atLeastOne", "no.feedback")
                return false
            }
          }
          return true             
        })           
        username(nullable:false, blank:false)
    }
}

Is there a better way to

• validate a related/group of fields (at least one can't be blank, 2 should have values, etc)?
• a groovier way to express "at least one shouldnt be null/blank" rather than my gross if-statement block?

Thanks

Answer 1

The Extended Validation plugin also adds support for instance validators, which allow to define constraints over several field without defining an artificial flag field or without repeating the validator for each field involved.

Answer 2

validate a related/group of fields (at least one can't be blank, 2 should have values, etc)?

Try this:

if ( (form.textarea1?.trim() ? 1 : 0) +
     (form.textarea2?.trim() ? 1 : 0) +
     (form.textarea3?.trim() ? 1 : 0) < 2) {
     err.rejectValue("atLeastTwo", "no.feedback")
     return false
}

a groovier way to express "at least one shouldnt be null/blank" rather than my gross if-statement block?

This is slightly Groovier...

if (!( (form.textarea1?.trim() ?: 0) ||
     (form.textarea2?.trim() ?: 0) ||
     (form.textarea3?.trim() ?: 0) )) {
     err.rejectValue("atLeastOne", "no.feedback")
     return false
}

Answer 3

WRT validating a group of fields, you could assign the validator closure to one of the fields. You don't need any extra/ficticious field. If it's going to be used often, create a plugin http://www.zorched.net/2008/01/25/build-a-custom-validator-in-grails-with-a-plugin/ or use a plugin for constraints http://grails.org/plugin/constraints

About grooviness I'm not an expert. But the safe navigator operator ?. makes unnecessary to ask for null

if ( form.textarea1?.isAllWhitespace() &&
     form.textarea2?.isAllWhitespace() &&
     form.textarea3?.isAllWhitespace() )
     {
          // They havent provided ANY feedback. Throw an error
          err.rejectValue("atLeastOne", "no.feedback")
          return false
     }

Answer 4

You can use the min-criteria plugin for that. http://www.grails.org/plugin/min-criteria