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
> >
> >
>
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