Re: How to validate TextBox fields?

On Monday, January 7, 2013 3:45:53 PM UTC+1, membersound wrote:

Yes I know this side. But it still does not tell me:
- how to validate the name before creating the person object (which I'm looking for in terms of numbers like int age; There I'd first like the validator to catch if it's a valid age before creating the person object)

If you want to use the annotations that are on your Person fields, then you have to create a Person object.

Technically, I believe you could generate code, the generator reading the annotations and producing code that will be able to validate data before creating the Person object, but there's no such things in GWT proper.

That being said, creating a Person object shouldn't be that expensive that you want to avoid it a all costs.

- how to display an annotation error message beneath a textbox

Well, use an Image widget? or a Label widget? call addStyleName on the textbox?

You'd still have to manually "map" the error to the appropriate widget though.

 

Could you help me out?

The easiest is probably to use the Editor framework:

• Each Editor has the possibility of doing some validation by itself (implement HasEditorDelegate and then call reportError on the EditorDelegate; if you want to do that only on flush() rather than dynamically as the textbox value changes, then implement ValueAwareEditor)
  
• errors passed to EditorDriver#setConstraintViolations are automatically mapped to the corresponding editors, which can implement HasEditorErrors to be notified and display the errors (the way they want); ValueBoxEditorDecorator is one such widget provided out-of-the-box (though not configurable so you'll generally want to build your own)

Your onClick will then:

1. flush()
2. check errors from editors
3. possibly validate using javax.validation, and then call setConstraintViolations to display them (beware that it then clears the one reported by editors themselves, you have to merge both lists of errors)

Using the Editor framework though you'll be editing an existing Person object (and/or create an empty Person object specifically to edit it and save it later), which also means it has to be mutable.

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