David,
Barracuda does this nested Exception procedure (as I believe you
probably know already). I've been playing with their forms package a bit
in a Struts app of mine. I like the scheme, in general, but the problem
I have with their particular implementation is as follows... The
Validator classes that throw the ValidationExceptions set the exception
message to be a resource key. At some point in the Action class I check
for validation exceptions and iterate through any that exist. I use
getMessage() to get the key and add a new ActionError to the
ActionErrors object. The problem comes with messages that need
substitutions. If I have a resource message like "Date should be between
{0} and {1}" I need some scheme for the Validator class to communicate
the specific parameters that go along with the resource key. Seems to me
that the ValidationException class needs a property like
MessageArguments (possibly an array of Objects, since that is ultimately
what MessageResources needs) that the Validator class can set and the
Action class can get as it iterates through the exceptions.
I've coded extensions to the Barracuda classes for this, but it's
awkward and means I need to always use my own versions of Validator
classes.
On the Struts side of things, I find that if I have a resource key and
an array of Objects that are the substitutions to be used in the
message, there's no ActionError constructor that will let me pass in the
array. Instead I have to manipulate things and use one of the existing
constructors that specify each replacement value explicitly. Of course I
could extend and make my own, but it seems reasonable that ActionError
should have such a constructor. It would also permit more than 4
substitutions, if anyone would need more.
Just my thoughts,
Will
----- Original Message -----
From: "David Winterfeldt" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, June 20, 2001 3:05 AM
Subject: Re: validation in the form vs. validation in the business
domain object
> Someone I know extended Exception and they throw
> nested exceptions that eventually are passed back to
> the Struts layer and then an ActionError is
> constructed for each exception. Something like that
> seems like a clean way to keep things separated. I
> did something similiar on a project with a Swing and
> EJBs.
>
> David
>
> --- James Hoffa <[EMAIL PROTECTED]> wrote:
> > What ideas do people have about where is the best
> > place to perform validation of items that come back
> > from ActionForms?
> >
> > Example: check to see if the user's choice of
> > motherboard, memory, and cpu are compatible with
> > each
> > other.
> >
> > Following the struts example, it seems like the
> > validate() method in an ActionForm is used only for
> > light validation (i.e. checking to see if something
> > was left blank, or checking for alpha and numeric
> > chars). This approach seems correct to me, since
> > there
> > should not be business logic inside the ActionForm.
> >
> > That leaves most of the work to the business domain
> > object since any nontrivial application will not
> > have
> > business logic in the Action class either.
> >
> > The business domain object, in many cases, will be
> > accessed remotely from the Action class.
> >
> > Does it make sense for the business domain object to
> > return an ActionErrors object(it is serializable)?
> > I
> > am not 100% comfortable yet with the idea of
> > importing
> > ActionErrors into the business object since it
> > couples
> > it to struts to a certain extent, and it could
> > potentially be large.
> >
> > Is the only alternative to send back a list of
> > generic
> > error codes from the business object that each map
> > to
> > an ActionError and the Action class could add the
> > ActionErrors? (i think i'd rather import
> > actionerrors
> > in this case)
> >
> > What are some of the "best practices" people have
> > found to work for this problem?
> >
> > Craig and ALL Struts creators: Struts is really
> > great. Thank you for all of your hard work. It is
> > definitely something to be proud of.
> >
> > __________________________________________________
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>
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