Personally, I would make the Address bean a second object, at least
temporarily. Once a validated Address had been entered, I would merge it
with the product bean in the session, and proceed from there.
-Ted.
Ronald Bakker wrote:
>
> Hello everybody,
>
> First, I want to apologise for the fact that my previous message was
> posted multiple times in this mailing list. Our sendmail log sent it
> only once, so I do't really understand what went wrong.
>
> Back to the issue. Consider the following case we're dealing with in our
> application:
>
> We're working on an e-commerce application with which people can order
> different kind of products. Ordering a product consists of two parts:
> first they have to fill in a product specific form to get a price quote
> for the requested product. Then, if they accept the quote, they have to
> fill in address information for delivery. Filling in address information
> uses the same form for all different products.
>
> What we want to do is the following:
> For each product, we define an action in struts-config.xml. Each action
> uses an own, product specific form, say productAFrom, productBForm
> etcetera. Each of these forms is an extension of an abstract class
> productForm.
> For the address information part, we want to define one additional
> action in struts-config.xml, which uses the abstract productForm as
> form-bean.
>
> Since filling in the address information form always follows the product
> ordering form, we know that the user always has a productForm stored as
> attribute in his session.
>
> I do realize that this mechanism gives some more responsibility to the
> developer, in that he has to be careful using an abstract class name as
> the type of a form bean, but I don't know any better alternatives yet.
> Maybe using the same conventions as jsp:usebean, create a new instance
> of an action form only if a 'class' attribute is present, if just a
> 'type' attribute is present only try to recycle existing instances.
>
> Any suggestions?
>
> Ronald Bakker
> Virgil PM&C
>
> "Craig R. McClanahan" wrote:
> >
> > On Mon, 6 Aug 2001, Ronald Bakker wrote:
> >
> > > Hi everybody,
> > >
> > > In Struts, form-beans can be described by 'name' and 'type'. Looking at
> > > method 'processActionForm' in ActionServlet, I conclude that roughly the
> > > following is happening (correct me if I'm wrong):
> > >
> > > When trying to find a form-bean from a mapping, Struts tries to find an
> > > attribute with the given 'name' in the scope that is defined for this
> > > mapping, if the class name of the found attribute is equal to 'type' it
> > > will reuse this found attribute. Otherwise a new form-bean instance of
> > > class 'type' is created and placed in scope.
> > >
> >
> > That's a correct understanding.
> >
> > > To my opinion, one fallback of this implementation is that you are
> > > forced to use the implementing class name of the form-bean you intend to
> > > use, you are not able to use an interface or abstract class name. Is
> > > there any chance Struts is going to use a more flexible way of
> > > retrieving form-beans from a mapping? I would like Struts to use the
> > > same mechanism as jsp:useBean, where you are more flexible in using
> > > beans with either 'type' or 'class'.
> > >
> >
> > Remember that <jsp:useBean> has a restriction -- if the bean is not
> > already there in the correct scope, you *must* have specified the actual
> > class name so that <jsp:useBean> can instantiate it. Struts will often
> > (and, if you're using request scope form beans, *always*) need this
> > information anyway, for the same reason.
> >
> > > Right now, we replaced this part of processActionForm with an own
> > > mechanism of reusing form-beans:
> > >
> > > /**
> > > * Original Struts code:
> > > */
> > >
> > > // Can we recycle the existing form bean instance?
> > > if ((instance != null) &&
> > > className.equals(instance.getClass().getName())) {
> > > if (debug >= 1) {
> > > log(" Recycling existing ActionForm bean instance of class '"
> > > + className + "'");
> > > }
> > >
> > > return (instance);
> > > }
> > >
> > > /**
> > > * Replaced by our code:
> > > */
> > >
> > > // Can we recycle the existing form bean instance?
> > > try {
> > >
> > > if ((instance != null) &&
> > > Class.forName(className).isInstance(instance)) {
> > > if (debug >= 1) {
> > > log(" Recycling existing ActionForm bean instance of class '"
> > > + className + "'");
> > > }
> > > return (instance);
> > > }
> > > }
> > > catch (ClassNotFoundException ce) {
> > >
> > > if (debug >= 1) {
> > > log(" Class not found: '" + className + "'");
> > > }
> > > return null;
> > > }
> > >
> >
> > I can see what you're after, but won't this only work in the case of
> > session beans that were previously created by an Action? For anyone else,
> > you'll just get an instantiation error.
> >
> > Note to self -- if we change the logic here, a similar change will be
> > needed inside the <html:form> tag, which can also create the form bean
> > dynamically if needed.
> >
> > > Ronald Bakker
> > > Virgil PM&C
> > >
> >
> > Craig
