Validation and the Visitor

From: Dagfinn Reiersol (dagfinn_at_howamazing.com)
Date: 08/11/04 

Date: Wed, 11 Aug 2004 11:14:21 +0200

I was interested to see the comments on user input validation in the
3-tier thread. I have a sneaking feeling that the subject is an
under-focused one and that it it both common enough and unique enough
that it needs its own "theory of validation" or perhaps its own design
patterns.

There is a recent article in Java World on "Validating value objects":

http://www.javaworld.com/javaworld/jw-06-2004/jw-0614-validate.html'

(Note: This is the term "value object" in the J2EE patterns sense.)

The example uses the Visitor pattern. My problem is I'm unable to see
how the Visitor is actually necessary. To me it looks like just a fancy
and pretentious way of passing the validatable object to the validator.

I'm not a Java programmer, so I may have missed something. Would anyone
care to have an opinion on it?

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