Re: [cgiapp] Redirect question

[Sean Davis <suppressed>]

On Jan 7, 2005, at 12:59 PM, Michael Graham wrote:

> > I am using CGI::App in a mod_perl environment.  I typically have
> > run_modes submit back to themselves for validation, etc.  If the form
> > information "passes", I return $self->next_run_mode (just an example).
> > I have made a couple of changes to my previous coding style.  First, I
> > am using path_info to get the runmode (makes linking and handler
> > dispatching much simpler).  Second, because of the first, I want to 
> > use
> > redirects to move from one run_mode to the next; that is, a form
> > submits back to itself and is validated, I do a
> > $self->redirect('next_run_mode').  It seems that redirects do not
> > conserve the POST information.  Is this true?  If so, does this sound
> > familiar to others?  What other coding idioms do people use besides
> > submit-to-self?
>
> I think the "submit-to-self, then redirect" method is the cleanest.  
> Not
> always the best performing (because you have two HTTP requests after a
> successful submit), but this method creates the fewest problems for
> browsers and for your application.

I do like the submit to self because all my code for validation, state 
changes, etc., is then relatively self-contained.  At this point, 
almost all my databases are read-only (with the exception of 
user-management), so I'm not too worried about the double submit issue 
for that type of data (which I can catch with a simple uniqueness 
check).

> So because of this, I'm trying to follow this rule of thumb:  use POST
> for submitting data that changes the state of the application and GET
> for requesting pages without changing the app's state.  That's more or
> less what the HTTP spec tells you to do anyway, AFAIR.
>
> As I understand it, your main problem with this approach is that
> "redirects do not conserve the POST information".  Which POST
> information are you trying to conserve?
>
> You can add query params to the redirect URL, so you can pass a small
> amount of state information that way.

Adding the information as a GET is something that I could certainly do. 
 As an example, I have a form that allows users to do a query (give the 
parameter for a SQL statement).  The display on the next page can be 
configured via multiple parameters (about 8, a couple that allow 
multiple values).  It is this information that I would like to hang 
onto.  One possibility is to store these parameters in a session, but 
if the user does a back a few times and resubmits a page that has 
session information from a later page, the results might be unexpected. 
 I could stuff all of this into a GET (I'm fairly sure the resulting 
string wouldn't be too long?), and perhaps that is what I should do for 
the redirect.

For an example, I wrote a quick database for gene expression profiles.  
We have a quirky access for it (you apply to via email submission 
rather than automatic), but it is available.  As you can see from the 
URL, it is not mod_perl based and has somewhat limited functionality 
compared to what I am currently trying to develop.

http://ntddb.abcc.ncifrcf.gov/cgi-bin/nltissue.pl

Thanks for all the insight from the group....

Sean


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