RE: validation philosophical question

[Adam Levine]

If you reread my post, you'll see the validation happens only in one spot, 
and that's in the business logic area. This keeps the same validation logic 
present, regardless of the presentation layer.  AFAIK, the Validation 
framework Struts provides should only be used as a cursory check (is this 
box filled in, is this a number) for use within the browser portion.  And, 
again, this ties it only to the presentation layer -- which means if you use 
another interface, ie wap/braille/DTMF/IVR, you're going to have to 
duplicate the validation for that layer.

From: "Yansheng Lin" <[EMAIL PROTECTED]>
Reply-To: "Struts Users Mailing List" <[EMAIL PROTECTED]>
To: "'Struts Users Mailing List'" <[EMAIL PROTECTED]>
Subject: RE: validation philosophical question
Date: Thu, 14 Aug 2003 11:29:11 -0600
Agreed mostly, but...

what happens when you want to change some validation rules?  You have to 
change
two or more places instead of one if you choose to use other validation 
methods
instead of keeping everything inside the validator framework.  The goal of
validator framework is to eliminate these redundancy.  Making sure 
everything is
kept inside of the config file, you only need to modify one place.

- Yansheng

-----Original Message-----
From: Adam Levine [mailto:[EMAIL PROTECTED]
Sent: August 14, 2003 10:43 AM
To: [EMAIL PROTECTED]
Subject: Re: validation philosophical question
My personal preference is there should be as little reliance on the
front-side as possible.  I personally hate little JS boxes popping up at me
"this entry isn't right.. fix it!", and much prefer a submit-correct cycle
with quiet, unobtrusive indicators showing me what I need to change.
If you insist on front-side validation (which, yes, can make the user
experience better), you should ALWAYS have backup/duplicate server-side
validation.. otherwise, what happens for the browsers/users who 1) don't
have JS enabled, 2) don't have JS functionality ?
As for where the appropriate place is business side.. That's dependent upon
your system design.  My Actions merely act as a gateway to business objects
that handle data validation.  If the data isn't right, I aggregate a list of
custom exceptions ('UserLoginNameAlreadyExistsException') to be handed back
to the Action caller, and return to the caller w/o performing any more
business logic.  The action caller checks that list for entries, and
accumulates form field error messages appropriately, and then
forwards/returns (actionmapping)  to the entry page.
if the business logic generates no custom exceptions, i perform the business
logic as appropriate (ie, updating/creating an entity bean, and return an
empty list to the caller.
if i have a system level problem (EJB/JNDI/something systematic that just
doesn't work), I throw a custom generic exception (ie,
UserCreationException) for the calling process to catch.  the action can
then populate the errors with a generic process error message ("there was a
system problem trying to create your account. try again or send an email
to....").
The point of all this is my data validation is kept in one place so I can
swap the interface as needed.  The only commonality between all interfaces
would be the use of an ActionForm and a List to hold returned validation
'exceptions'.  And I have no problem with that. the Form is just a POJO for
all intents and purposes, as it should be.   This leaves my interface to be
business logic stupid, but interface/UI logic smart.
my $0.02.

From: "David Thielen" <[EMAIL PROTECTED]>
Reply-To: "Struts Users Mailing List" <[EMAIL PROTECTED]>
To: "Struts-Users" <[EMAIL PROTECTED]>
Subject: validation philosophical question
Date: Thu, 14 Aug 2003 10:31:27 -0600
Hi;

Everyone who hits my site has a high-speed connection. So I am thinking that
it makes sense to do server side validation only as that provides a better
method than the javascript pop-ups.
And in this case, it seems to me that the logical place for all validation
then is inside the ActionForm validate method.
comments?

thanks - dave

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