I guess that's the critical part, eh-- sorry for the hand-waving :)
At this point, I see the Struts controller coordinating these "rules", based
on the contents of struts-config.xml:
1. Instantiation of our form-bean as needed (no real change here).
2. Instantiation of optional change-listeners* associated with our form.
(peek at the xml fragment below)
3. Now, it can register the change-listener (aka
VetoableChangeListener), with our new form-bean.
note: add<PropertyName>VetoableChangeListener
& remove<PropertyName>VetoableChangeListener
adhere to a naming pattern established by the JavaBeans spec.
for more on this, see the last section on this page:
http://java.sun.com/docs/books/tutorial/javabeans/properties/constrained.htm
l
Assuming that this is all happened smoothly, which I think is pretty safe,
that leaves the following main question:
-- What happens when Struts begins to populate our action form?
A. Nothing, our users suddendly started getting everything "right", so our
Validators never complain about their input anymore.
B. Our, the more probable route... our Validators start throwing
PropertyVetoExceptions because our user's aren't any better at answering
these questions than we are :)
This point introduces the next responsibily I planned on handing the
struts-controller: handling PropertyVetoExceptions. In short, I'd like it to
basically turn these exceptions into ActionErrors for us.
Hope this sounds a little clearer, thanks for the feedback-- I think it
greatly influences the ideas quality.
Regards,
Levi Cook
> > <struts-config>
> > <!-- etc.. -->
> > <form-bean name="myCCForm" type="MyCCForm">
> > <change-listener
> > property="creditCard"
> > type="CreditCardValidator"
> > />
> > </form-bean>
> > <!-- etc.. -->
> > </struts-config>
----- Original Message -----
From: "Jonathan Asbell" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, June 21, 2001 4:42 AM
Subject: Re: server-side, java-based validation rules for struts..
> Levi, you lost me somewhere in your explanation from ....."now have to
> account for interacting with Struts-- That's where I see
> java.bean.VetoableChangeListener........."
>
> What are you passing to whom, and where are you instantiating and
> registering things?
>
>
> > public MyCCForm extends ActionForm {
> > public setCreditCard(String newCreditCard) throws
PropertyVetoException
> {
> > vcs.fireVetoableChange(CC_PROP_NAME, creditCard, newCreditCard);
> > creditCard= newCreditCard;
> > }
> > public void addCreditCardVetoableChangeListener(VetoableChangeListener
> > lsnr) {
> > vcs.addVetoableChangeListener(CC_PROP_NAME, lsnr);
> > }
> > private String creditCard;
> > private static final String CC_PROP_NAME= "creditCard";
> > private VetoableChangeSupport vcs= new VetoableChangeSupport(this);
> > }
> >
> > public class CreditCardValidator implements VetoableChangeListener {
> > public void vetoableChange(PropertyChangeEvent evt)
> > throws PropertyVetoException
> > {
> > String creditCard= null;
> > try {
> > creditCard= (String) evt.getNewValue();
> > }
> > finally {
> > if(StringValidator.isCreditCard(creditCard) == false)
> > throw new PropertyVetoException("some.msg.key", evt);
> > }
> > }
> > }
> >
> >
