On Tue, Mar 25, 2008 at 2:05 PM, mickolka <[EMAIL PROTECTED]> wrote:
>
> Hi all
>
> I have created a middleware t track campaigns that do one simple thing
> - it get parameter from request and set cookie, code looks like
>
> class CampaignTrackingMiddleware(object):
>
> def __init__(self, app):
> self.app = app
>
> def __call__(self, environ, start_response):
> source_id = request.params.get('source_id')
> if not is_blank(source_id) and
> request.cookies.get('source_id') != source_id:
> # print "setting source_id cookie to %s " %
> request.params.get('source_id')
> response.set_cookie('source_id', source_id,
> expires=3600000)
> session.save()
> return self.app(environ, start_response)
>
> After I'm adding it to the chain in middleware.py
> I'm getting the error
> ..................................................................
>
> File "/opt/workspace/uaprom/uaprom/lib/custom_middleware.py", line
> 27, in __call__
> if not is_blank(request.params.get('source_id')):
> File "/sw/lib/python2.5/site-packages/Paste-1.4.2-py2.5.egg/paste/
> registry.py", line 125, in __getattr__
> return getattr(self._current_obj(), attr)
> File "/sw/lib/python2.5/site-packages/Paste-1.4.2-py2.5.egg/paste/
> registry.py", line 182, in _current_obj
> 'thread' % self.____name__)
> TypeError: No object (name: Request) has been registered for this
> thread
>
> As far as I understand request is not registered at that point, I
> tried to move my middleware to the top/bottom of the chain and the
> error was still the same. After all I moved the logic to the
> __before__ method of BaseController
>
> Is there any way to do such things in the middleware or BaseController
> is the right place for that?
>
> Thanks in advance for any help
> m
>
> Disclaimer: I came from J2EE world (I hope I never come back to that
> enterprise nightmare) and think that Middleware is ServletFilter
> analog, I might be wrong.
You have three choices.
1) Move the code to the base controller's .__before__ or .__call__ method.
2) Parse the parameters yourself using
cgi.parse_qs(environ['QUERY_STRING"]). If you want to delete
parameters, you can rewrite the query string with urllib.urlencode.
Don't use cgi.FieldStorage because it will use the actual environment
variables and standard input rather than the WSGI environment.
3) Call webob.Request(environ) to get the same type of request object
Pylons uses.
WebOb also contains a middleware class or decorator which makes
writing middleware much easier. You should probably use it.
If the request is POST, you'll have to figure out how to read the
input and then set it back the way it was for the application.
I don't know about J2EE, but middleware is intended for two purposes:
1) Features that are completely optional, that the application doesn't
realize are there. Pylons error handlers are an example of this, as
well as the static application at the bottom of middleware.py.
2) Services for the application, which can be used with a different
application just as easily. The Routes and session middleware are
examples of these. (They're hidden in Pylons 0.9.6, but in
middleware.py in 0.9.7-alpha).
Some would argue that only (1) is true middleware and (2) should be
called something else, but in any case both are useful. But if the
service is really specific to one application and not useful in other
applications, it belongs in the base controller rather than in
middleware.
I have been thinking about a heresy the past week, that instead of
improving WSGI maybe we should just leapfrog it to a WebOb-based chain
of servers, applicaiions, and middleware. Then the protocol could
just create the request/response once a the beginning of the chain and
let the middleware/application modify it rather than each middleware
having to reinvent the wheel and parse obscure environ keys. But
that's too radical to just do in Pylons right now.
--
Mike Orr <[EMAIL PROTECTED]>
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