On Thu, 13 Jun 2002, John Yu wrote:
> Date: Thu, 13 Jun 2002 17:18:31 +0800
> From: John Yu <[EMAIL PROTECTED]>
> Reply-To: Struts Developers List <[EMAIL PROTECTED]>
> To: Struts Developers List <[EMAIL PROTECTED]>
> Subject: RE: FormBeans ... as an Interface.
>
> At 09:54 pm 12-06-2002 -0700, you wrote:
> >Quite frankly, it baffles me when people want to use form beans as the
> >model. Doing this couples the model to the view in wholly undesirable ways.
> >
> >For instance, what happens when the UI designer moves things around in the
> >pages in such a way that the mappings between UI elements and pages (and
> >thus form beans) change? It seems that you'd have to change the model now,
> >just because the UI designer made some tweaks to the view. This kind of
> >coupling is entirely unacceptable in anything other than trivial apps.
>
>
> Not dispute about this. But, you can view it from the other angle:
>
> In my case, I want to use something from the model as the formbeans, not
> the other way round (as we all know having a model->view dependency is
> bad). However, because of the way formbean is designed in Struts, this ends
> up having the ActionForm class and the other dependent apis dragged into
> the model tier.
>
> So, to paraphrase my question: "Does it make sense to modify Struts such
> that it allows other objects (e.g. from the model tier) to participate the
> role of formbeans but does not create an ugly model->view dependency?"
>
> (The situation is like in Swing, a model object can implement a Listener
> interface and let the view components talk to them. This isn't regarded as
> a model->view coupling.)
>
Consider an integer property of your model bean, which you are going to
render as a text field due to the limitations of HTML. Consider a user
that types in "1a3" instead of "123", and thus causes a conversion error
when Struts attempts to store the property value. How do you plan to meet
the user's expectation, when the page is redisplayed, of showing what he
or she *did* type so that it can be corrected?
The preferred answer in Struts is to use a String property in your form
bean for this purpose -- conversion to the underlying model data types
should be triggered by the Action, after validation has been completed and
any business-layer checks have been performed.
Form beans have different purposes, different semantics, and different
lifetimes than model objects.
> --
> John Yu Scioworks Technologies
> e: [EMAIL PROTECTED] w: +(65) 873 5989
> w: http://www.scioworks.com m: +(65) 9782 9610
>
> Scioworks Camino - "Rapid WebApp Assembly for Struts"
>
Craig
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