No, I think you misunderstood :)
Let's say we are designing a wizard flow with three pages, plus one
"confirmation" page at the end. Each page has a single HTML form on it.
The first page has this in the form:
<input type="text" name="firstName">
The second page has this:
<input type="text" name="firstName">
And the third page has:
<input type="text" name="lastName">
(We're going to ignore the poor wizard design for the moment, we're
talking theory here :) ).
Now, let's say for the sake of simplicity you decide you want to have a
single ActionForm for all three pages. This isn't an unusual approach
for wizards. So, your ActionForm might look like:
public class myForm extends ActionForm {
private String firstName;
private String lastName;
// Getters and setter follow
}
Lastly, assume that all the action mappings involved here reference the
same session-scoped ActionForm, which is exactly what we intend (think
of the ActionForm as collecting all the input through the entire wixard
flow). Now, let's walk through what happens:
* Page 1 is shown, user enters "Frank" in firstName textbox. User
clicks submit.
* At this point, the ActionForm in session now has firstName="Frank".
* Page 2 is shown. User now enters "Brad" in firstName textbox. User
clicks submit.
* At this point, the ActionForm in session now has firstName="Brad".
* Page 3 is shown. User enters "Zammetti" in lastName textbox. User
clicks submit.
* At this point, the ActionForm in session now has lastName="Zammetti".
* The confirmation page is shown. Let's say that there is a button to
go back to page 1 now, and the user does so. What do they see? They
see "Brad" in the firstName field, even though on page 1 they entered
"Frank". It's easy to see why it happened, but to the user their data
got corrupted.
Again, you have to ignore the bad wizard design... I'm just too lazy to
think of a better example :)
That's the scenario I was referring to. Does that make sense? :)
Frank
[EMAIL PROTECTED] wrote:
I hope I understand what you are asking. A couple of things come to mind about threads and Servlets. If one uses Instance variables in Servlets then each instance of that Servlet has a unique variable and there is no data corruption. However if one uses Class variables then each instance of a servlet shares the variables and then data corruption can occur.
Same with formbeans and wizards. Each formbean is unique to the specific
Servlet action. So, if one uses a single formbean for several steps in a
wizard then there is no data corruption.
Am I understanding what you are asking?
--Brad.
-----Original Message-----
From: Frank W. Zammetti [mailto:[EMAIL PROTECTED]
Sent: Wed 11/16/2005 11:46 AM
To: Struts Users Mailing List
Subject: Wizard page "data corruption" (was: "Re: Form Beans")
Imagine you have a single ActionForm with a firstName field. Now
imagine you have two wizard pages that are used in sequence, and you
want to use the same ActionForm for both.
Assume the form is stored in session, as you would expect in a wizard.
Now, imagine there is a firstName field on both HTML forms of both
wizard pages... you might argue this isn't a good wizard design, and I
would tend to agree, but it's something that can happen in some cases.
Now, assume a prototypical Struts app, no Struts Dialogs extensions or
anything...
What happens when the first page submits? The firstName field is
populated in the ActionForm. Now what about when the second form is
submitted? The value of the firstName field in the ActionForm now has
the value from the second form submission, effectively overwriting the
value the user entered on the first page, so if the user were to go back
to the first wizard page, they would incorrectly see the data from the
second page in effect. Easily to explain, but to the user it's a data
corruption issue.
This is the scenario I was referring to. Does your Dialogs stuff
overcome that? If so, how? Whether it does or not, a "normal" Struts
app will certainly have this problem, hence my comment about making sure
the field names are different... in this case, it might be as simple as
making two fields in the ActionForm, one named firstNamePage1 and
firstNamePage2.
Frank
Michael Jouravlev wrote:
On 11/16/05, Frank W. Zammetti <[EMAIL PROTECTED]> wrote:
The one thing to keep in mind if you go [one ActionForm] route is
to be sure you don't have a field on one page
with the same name as another. I had one junior developer make that
mistake and it drove him nuts trying to figure out what was wrong
(obvious in retrospect, but one of those "tricky at the time" problems
to solve).
I don't see right away how does this matter if you have separate
submits from a browser each time. Also would not matter if you
redirect between pages and don't intentionally stuff values into
redirected request. Redirected request comes clean, so same fields or
not - does not matter. This is why my two-phase request processing
works: POST comes with input data, form is populated, then I redirect
to the same action again, GET comes clean, form is not updated because
request contains no data.
Forwarded request brings all input data with it, and Struts applies
this data to another form. Been there ;)
Michael.
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Frank W. Zammetti
Founder and Chief Software Architect
Omnytex Technologies
http://www.omnytex.com
AIM: fzammetti
Yahoo: fzammetti
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