It allows you to handle simple validations outside of the Action class, which would only be called when there's data that can be passed to the business tier (which may, among other things, perform business validation). Also, as the Validator plugin shows, it enabled declarative validation. So now, we don't even have to write validation code in our action forms. By the time execution reaches the Action object, it can go straight to conversion without having to worry about ParseException or NumberFormatException.
Hubert On Fri, 18 Mar 2005 17:47:14 +0000, Lawrie Gallardo <[EMAIL PROTECTED]> wrote: > I appreciate that there are different levels of validation - I just can't > see why any of them are better handled by ActionForm (which could otherwise > just be a dum strut object/ map / etc) than by Action. Surely it is better > to keep all your presentation tier validation together in one place where > possible (although obviously you want to keep your business logic validation > with your business objects)? > > Lawrie > > >From: Hubert Rabago <[EMAIL PROTECTED]> > >Reply-To: Hubert Rabago <[EMAIL PROTECTED]> > >To: Struts Users Mailing List <user@struts.apache.org> > >Subject: Re: Wouldn't validation be better performed by Actions rather than > >ActionForms? > >Date: Fri, 18 Mar 2005 11:27:11 -0600 > > > >You raise a lot of points, and I admit I won't be able to respond to > >all of them in one email (due mostly to time constraints). Besides, > >there are others who could respond, so I'll leave some out for them. > >:) > > > >There are/can be different levels of validation. Some validation you > >perform before others. For example, an HR entry screen might contain > >a field for salary. You would validate that the field contains a > >valid String that can be converted into a double, and you'd also make > >sure it doesn't exceed certain bounds (like, say, USD 10,000,000 for a > >junior programmer). If the field doesn't contain a valid double, > >there's no sense checking its value boundaries. The field itself is > >not syntactically valid. This level of validation is what's most > >often assigned to the ActionForm. Much of these can be > >automated/declared and oftentimes the Action doesn't even need to > >participate. Hence, we let the ActionForm carry out this part, and if > >it fails at this level, we don't even bother calling the Action. > > > >Hubert > > > >On Fri, 18 Mar 2005 17:17:39 +0000, Lawrie Gallardo > ><[EMAIL PROTECTED]> wrote: > > > I'm still relatively new to Struts, but I can't help but feel that > > > validation would be better performed by Action classes rather than > > > ActionForm classes. > > > > > > It seems to me that, ideally, you want > > > 1. Validation, > > > 2. Transformations (ie convert separate day, month and year HTML fields > >to > > > Java Date object), and > > > 3. Mapping of ActionForm fields (/HTML parameters) to Domain POJOs / > >DTOs > > > to all be configured in the same config file (to minimise duplication) > >and > > > to be implemented in the same class rather than scattered between > >multiple > > > config files and classes. > > > > > > Now, if my understanding is correct: > > > 1. There is always a one-to-one mapping between an ActionForm and an > > > ActionMapping, > > > 2. Struts best practice is to have each Action class handle all possible > > > operations for the HTML request it deals with using DispatchLookupAction > >or > > > something similar, > > > 3. Almost noone creates ActionForms manually any more - they use > > > DynaActionForm (or validating variations of this). And for those who do > > > still create ActionForms manually, they don't offer anything in the way > >of > > > reuse, and are basically throw-away classes. > > > > > > Now if this is the case, would it not be better to have the ActionForm > >as > > > basically a dum data holder and have the validation method in the Action > > > classes instead? The strus-config.xml file could contain all the > >required > > > declarative validation, transformation and mapping info, and the Action > > > class could contain any validation, transformation, and mapping > >operations > > > that were too complicated to be set up declaratively. > > > > > > Is it just down to design decisions made in early versions of Struts and > > > backward compatibility that things are the way they are? Or are there > >good > > > arguments for having the validation method in ActionForm? Am I missing > > > something here? > > > > > > >--------------------------------------------------------------------- > >To unsubscribe, e-mail: [EMAIL PROTECTED] > >For additional commands, e-mail: [EMAIL PROTECTED] > > > > _________________________________________________________________ > It's fast, it's easy and it's free. Get MSN Messenger today! > http://www.msn.co.uk/messenger > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
