Re: Form Validation

Hi,Diez
  Thanks a lot for your anwser.Btw,Ming Peng is my full name.This is 
ajusted to English custom.In China,my name is 褰 and it sounds---Peng 
Ming.:)


>From: "Diez B. Roggisch" <[email protected]>
>Reply-To: [email protected]
>To: [email protected]
>Subject: Re: [Barracuda] Form Validation
>Date: Wed, 2 Jul 2003 22:36:24 +0200
>
>Hi Ming (or Peng? I'm not sure which name is the first name in 
chinese/asiatic
>names),
>
> >   You can see the code in "LoginScreen.java" of the DiscRack sample.If 
I
> > click the "Submit" without filling the "username" field which has the
> > NotNullValidator,will the "LoginValidator" execute?If "yes",will I get 
the
> > Exceptione for the "null" problem?If I comment out the code---
> > if (user != null && password != null)---It seems a NullPointException 
will
> > be thrown.But this special code is for the validation for "Null input" 
and
> > a validator for forbiding "blank input" has been defined.Is that 
redundant?
>
>There are two types of validators: FormElementValidators, which are 
attached
>to a single form element, and FormValidators, which are attached to the 
whole
>form.
>
>From the javadoc:
>
>-------
>public FormMap validate(boolean deferExceptions)
>                  throws ValidationException
>
>Validate the entire form (both form level and elements). We start by 
invoking
>form validators which apply to individual form elements, then we invoke 
any
>which apply to the entire form
>------
>
>So you are right: The LoginValidator is called after all the
>FormElementValidators have been called, even if one of them fails.
>
>But this is not redundant (as long as you're code in the validators isn't
>redundant): Lets assume a Form for registering a new user. It contains 
three
>elements: NAME, PWD, PWD_CONFIRM.
>
>Now the user must specify an entry for all three of them, so there's a
>NotNullValidator on all of them. Also PWD=PWD_CONFIRM must hold, so you
>define a custom FormValidator that ensures that.
>
>Now if the user enters different PWD and PWD_CONFIRM and _no_ NAME, the
>NotNullValidator of NAME will throw an exception, and the FormValidator 
will
>complain about not-mathching passwords. So you can supply your user with 
all
>neccessary informations at once.
>
>I admit that this example is a little bit misleading, as password-fields
>aren't subject to repopulation. But think of an arrival and departure-date
>whe arrival < departure has to hold.
>
>However, if you only want to allow for form-wide validation when all the
>element-wise validation has succeeded, you can always call
>
>try{
>  validateElements(true);
>  validateForm(true);
>} catch(ValidationException ex) {
>...
>}
>
>Regards,
>
>Diez
>
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