[mod_python] how to handle xforms with publisher handler

Graham Dumpleton grahamd at dscpl.com.au
Thu Jan 11 21:00:20 EST 2007

Jim Gallacher wrote ..
> Emiliano Moscato wrote:
> > Hi all!
> > 
> > I'm getting crazy trying to receive xforms xml data with mod_python +
> > publisher handler.

In what way are you using mod_python.publisher? Depending to what
degree you are using it, mod_python 3.3 offers some alternate mechanisms
for doing basic dispatch against different resources which might be more
useful and allow you to still access content of response to decode it.

> > In a normal HTML form, the data would be sent as
> > application/x-www-form-urlencoded, in the XForms world however, this
> > information is sent as XML formatted data (application/xml).
> > Up to now I've used cherryPy as web server and I've got my xml data with
> > cherrypy.threadData.xform.
> > I've read that PHP receive this in $HTTP_RAW_POST_DATA variable. If I
> send
> > the form to a php script all work fine.
> > But when I try to submit a xforms with method POST to a script managed
> by
> > publisher handler I get an error with no log in my apache server error
> log.
> > Any help?
> You'll need to elaborate on the error you are getting, but I think part
> of the problem is that you are bumping up against part of the internal
> "magic" of publisher.
> Publisher automatically creates a FieldStorage instance. Unfortunately
> FieldStorage assumes that the content-type starts with either 
> "application/x-www-form-urlencoded" or "multipart/". If I had to guess
> I'd say that you are getting "501 Not Implemented error" as a result.
> Here are a couple of solutions that you might consider as a workaround:
> 1. Hack util.FieldStorage to properly handle your content-type. If you
> do this feel free to submit a patch so FieldStorage can be fixed. ;)

Hmmm, xforms is quite different.


Looks like a lot of work.

> 2. Hack publisher to skip the automatic creation of FieldStorage. (Line
> 424 in publisher.py for mod_python 3.3.0b). You can then use req.read()
> to read and process the POST'd data within your content handler.

I've raised this issue before about publisher not being able to accept other
content types. See:


Also, like PSP now does, publisher could be made to use 'req.form' if it
already existed. This would allow a stacked response handler before
publisher to decide whether some other form content was supplied, decode
it and set req.form to a compatible class to FieldStorage. I don't know that I
have created an issue for that idea before, but have certainly thought
about it and perhaps mentioned it on the mailing list.

> 3. Use a PythonFixupHandler before the content handler. In the 
> fixuphandler use req.read() to grab the raw data and adjust the 
> content-type header so that FieldStorage doesn't bomb out. Note that if
> you want to pass xml field data as parameters to your handler method 
> you'll need to do a bit more work. For example
> def index(foo="bar"):
>      return "whatever"
> won't get foo from your xml data. You can likely work around this but 
> you'll need to take a look at the source for FieldStorage and publisher
> to work out a strategy.

If you are talking about modifying the input stream, an input filter would
perhaps be better. Not sure that that will help since xforms is quite
different and isn't just a matter of changing content type.


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