On Thu, 14 Jun 2001, Jonathan Asbell wrote:
> Craig, can you explain point number one "Expose the data as JavaBeans *other
> than* the form bean". Is it that you are not using the form bean?
>
Yes. I can think of many cases where you'd want to extract read-only data
from beans other than the form bean when building a presentation layer,
and I would feel pretty limited by a rule that said "all the dynamic data
you need for this page *must* come from the form bean".
Now, if the data is already present in the form bean and you want to use
it in a read-only fashion, that's OK too ... the important coordination
issue between the business logic and presentation logic layers is which
bean names you're using to communicate, and what properties are expected
in each bean.
Craig
>
> ----- Original Message -----
> From: "Craig R. McClanahan" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Thursday, June 14, 2001 1:19 PM
> Subject: Re: ActionForms for read-only data??
>
>
> >
> >
> > On Thu, 14 Jun 2001, hi there wrote:
> >
> > > Craig,
> > >
> > > The ActionForm class definition seems to imply that it was intended to
> > > contain only editable data (i.e., the reset and validate methods).
> > > Distinguishing between read and write functionality in the enterprise
> > > systems I have developed was always a major advantage, both in
> extensibility
> > > and code maintainability, as usually each type of functionality had
> > > different processing requirments. It seems that if we mix read and
> write
> > > functionality into one ActionForm instance, we will have some "bulky"
> > > classes to maintain. Any comments? Thanks.
> > >
> >
> > There are probably multiple reasonable approaches to dealing with
> > read-only data. Let's consider some of the ways you can do this:
> >
> > (1) Expose the data as JavaBeans *other than* the form bean:
> >
> > This is quite easy, since you can do things like <bean:write>
> > to generate the output, <logic:xxxx> to test, and so on.
> > However, you are mildly increasing the linkage between the
> > model layer and the view layer -- now the developers have to
> > agree on the bean name, and the properties to be used. The
> > tradeoff is that you might be able to reuse beans (such as
> > value objects in an EJB based app) that already exist.
> >
> > (2) Copy the read-only data into the form bean:
> >
> > This is particularly useful in several use cases:
> > - You only want to access the data nested inside the <html:form>
> > - You don't want to create the extra dependency on a bean name
> > (since you can reference the form bean implicitly)
> > - A particular property might be read-only in some uses of the
> > form and read-write in others (see the "username" field of the
> > RegistrationForm bean in the example application).
> > However, adding new properties means going back and updating the
> > form bean class every time, which can be tedious if it's not being
> > automatically generated.
> >
> > In practice, I have used both techniques -- but in particular I find
> > myself needing data outside the nested body of an <html:form>, in which
> > case I really need to use technique (1) anyway.
> >
> > Part of my internal system documentation (for the various developers) is a
> > clear description of the bean names (and scopes), and the properties that
> > they expose, that the page developer can count on. This seems to deal
> > with most of the manageability issues, but none of these apps have had a
> > very long life yet since Struts has only been around a year :-).
> >
> > Craig McClanahan
> >
> >
> > > >From: "Craig R. McClanahan" <[EMAIL PROTECTED]>
> > > >Reply-To: [EMAIL PROTECTED]
> > > >To: [EMAIL PROTECTED]
> > > >Subject: Re: ActionForms for read-only data??
> > > >Date: Mon, 11 Jun 2001 17:01:31 -0700 (PDT)
> > > >
> > > >
> > > >
> > > >On Mon, 11 Jun 2001 [EMAIL PROTECTED] wrote:
> > > >
> > > > > I have a Struts theory question on use of action forms versus java
> beans
> > > > > for read-only data.
> > > > >
> > > > > We have extended workflow on our website such that the same form can
> > > >look a
> > > > > bit different depending on where you are in the workflow.
> > > > > For example, the quote request will have limit and retention fields
> in
> > > >the
> > > > > business request section. Once you get to quote, those fields are
> > > > > read-only and there's an additional quote amount field. When the
> client
> > > > > requests binder, all those fields are read-only and there is a
> checkbox.
> > > > > Once bound, everything is read-only.
> > > > >
> > > > > There is some disagreement on the team as to how to handle this
> case.
> > > >We
> > > > > will obviously have four JSPs, one for each of these presentations.
> The
> > > > > question is the data mapping to beans.
> > > > >
> > > > > Half of the team feels that to use Struts in its purest sense, we
> need
> > > >to
> > > > > have java beans that represent the read-only data, and action forms
> to
> > > > > represent the editable data. That would mean four action forms, one
> for
> > > > > each JSP.
> > > > >
> > > > > The other half of the team wants to re-use the same action form for
> all
> > > > > four cases, bean:define it in the session, and use bean:write to
> print
> > > >out
> > > > > the data if read-only. The major advantage is simplicity - we have
> one
> > > > > bean that represents all of the data - there is no need to
> understand
> > > >what
> > > > > part of the workflow we are in when translating the data from the
> data
> > > > > model to the presentation layer beans. It is also easier to
> understand
> > > >for
> > > > > an HTML programmer or developer that the same bean is used
> regardless of
> > > > > whether it is a bean:write or any of the html tags.
> > > > >
> > > > > We certainly don't want to end up in a position where we have broken
> the
> > > > > framework and hurt our extensibility in future releases. The first
> > > > > scenario would seem to follow the framework more closely, but in
> this
> > > > > special case, is it a problem to deviate and use the ActionForm for
> what
> > > >it
> > > > > is - a bean?
> > > > > We would appreciate any advice and experiences.
> > > > > Thank you.
> > > > >
> > > >
> > > >Ted covered a couple of the issues in his response -- I'd like to add a
> > > >few more thoughts. I don't think there are cut-and-dried answers to an
> > > >issue like this, so it's a question of balancing the tradeoffs.
> > > >
> > > >If you are using the same JSP page itself for the different views of
> the
> > > >same information, you probably already have conditional logic in it
> about
> > > >whether to make a field editable or read only. In such a case, I don't
> > > >think it necessarily violates the Struts philosophy to use the same
> > > >ActionForm bean. In fact, the Struts example application includes a
> > > >miniature example of this use case like this:
> > > >
> > > > <logic:equal name="registrationForm" property="action"
> > > > scope="request" value="Create">
> > > > <html:text property="username" size="16" maxlength="16"/>
> > > > </logic:equal>
> > > > <logic:equal name="registrationForm" property="action"
> > > > scope="request" value="Edit">
> > > > <bean:write name="registrationForm" property="username"/>
> > > > </logic:equal>
> > > >
> > > >which makes the username field editable in create mode, but read only
> in
> > > >edit mode.
> > > >
> > > >Note that you do not actually have to use <bean:define> to introduce
> the
> > > >ActionForm bean if it's the same bean used in your <html:form> tag --
> the
> > > >standard Struts logic will introduce it for you. It can be used
> exactly
> > > >like any other bean, from within the nested body of the <html:form>.
> > > >
> > > > >
> > > > > Lisa Stephens
> > > > > GeneralCologne Re
> > > > > Trumbull, CT
> > > > > 203 328 5227
> > > > >
> > > > >
> > > >
> > > >Craig McClanahan
> > > >
> > > >
> > >
> > > _________________________________________________________________
> > > Get your FREE download of MSN Explorer at http://explorer.msn.com
> > >
> > >
> >
>
>
