Behavior of app layers wrt date/phone validation/conversion?

["Karr, David" <da...@attws.com>]

I'm sure this has been talked about many times, but I couldn't find a
succinct discussion about this in the archives.

The question is, what are the best, or common, practices with respect to
where and how validation and conversion is done between "view" values and
"model" values, and with date/phone values, in particular?

In my particular context, I'm not interested in how the Validator framework
should fit into this, only because the consensus opinion in my team was to
not use the Validator framework at this time (because they wanted to reduce
training/information overload).

I ask this partly to review the principles for myself, but also to get
information to back up my views on this in my team.

In my opinion, the form bean value should contain exactly the string that is
displayed in the browser.  The business logic layer, however, should contain
the value as it is represented in the domain layer, being a Date value or a
ten character numeric string (for a phone number).

The stickier question is where the conversion and validation is done, and
what layer "owns" the algorithms for this.  I think it's a good idea to have
the form bean "own" the conversion algorithms (define the from/to code in
form bean methods), but drive the validation process in the Action.
However, I believe there are different opinions on this.

I've heard that there are some people who believe the formatting and format
validation should be done in the business logic (below the Action), which I
find hard to believe.

With respect to phone numbers, there's some question about whether it's
better to provide a single text field to enter a phone number, or to have
three fields for the three pieces of the number.  If the single field is
used, then the value stored in the form bean would be like "(nnn) nnn-nnnn"
(if you assume that the form bean stores exactly what is displayed on the
screen), and you use javascript on "blur" to convert an entered ten-digit
string to the proper format.  If three fields are used, the formatting is a
little easier, and the only javascript (if at all) is to set focus to the
next field when the field fills up (so they can enter ten digits
consecutively without stopping).

I'd appreciate people's carefully crafted opinions on this, and any useful
references.

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