ActionForms for read-only data??

[ls...@gcr.com]

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.


Lisa Stephens
GeneralCologne Re
Trumbull, CT
203 328 5227

Re: ActionForms for read-only data??

[Ted Husted <hu...@apache.org>]

This is off the original topic, but speaking of multiple beans, I
thought I would mention that since the Struts tags support a nested
syntax, beans can be properties of ActionForms. 

<html:hidden property="table1.account">
<html:hidden property="table2.customerName">

This would map to table1.getAccount() and table2.CustomerName() -- where
table1 and table2 were JavaBean properties of your ActionForm (including
ActionForms!). 


-- Ted Husted, Husted dot Com, Fairport NY USA.
-- Custom Software ~ Technical Services.
-- Tel 716 737-3463.
-- http://www.husted.com/about/struts/

Re: ActionForms for read-only data??

[Ted Husted <hu...@apache.org>]

The important thing about ActionForm beans is that they are intended as
adapters between HTML forms and the rest of the application. If the
property is being used within a HTML form, then it is a valid use of an
ActionForm bean, regardless of whether the property is hidden or
immutable. 

It is not expected that there will be a 1:1 relationship between a HTML
form and an ActionForm bean. Some ActionForm beans may be used on
several forms, and several forms may use the same ActionForm bean. In
general, most people would design ActionForm beans to represent a
logical view (in the SQL sense) within the application. If the data is
being accessed by the same SQL query, then it would make sense to put it
all on the same ActionForm bean, regardless of whether it is exposed.

The only thing to watch for is Strut's calling reset() as part of the
validation. If a property is not present in the form, then it will be
reset, and your validation has to cope with that.

One caveat: ActionForms are not meant to be a panacea for the
presentation layer. There are often other JavaBeans in play on this
layer, with ActionForms being specialized for use with HTML forms.

-- Ted Husted, Husted dot Com, Fairport NY USA.
-- Custom Software ~ Technical Services.
-- Tel 716 737-3463.
-- http://www.husted.com/about/struts/


lstephe@gcr.com 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.
> 
> Lisa Stephens
> GeneralCologne Re
> Trumbull, CT
> 203 328 5227

Re: ActionForms for read-only data??

["Craig R. McClanahan" <cr...@apache.org>]

On Mon, 11 Jun 2001 lstephe@gcr.com 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