repoze.bfg.httprequest 0.4.2

Description:

repoze.bfg.httprequest 0.4.2

Overview
The motivation for this package is to encourage the use of request
type adaptation instead of depending on packages with request type
definitions.
Instead of subclassing the request interface, we encourage an
adaptation pattern:

>>> from repoze.bfg.interfaces import IRequest
>>> IGZipRequest = IRequest({'http_accept_encoding': 'gzip'})


An event handler listens for the INewRequest event and
automatically marks the request with interfaces as needed to adapt the
request to the request types that it may apply for.
To complete the example above, a request would come in with an HTTP
environment like the following:

{‘http_accept_encoding’: ‘compress, gzip’}

Since we’ve previouly adapted the request to an accept-encoding of
‘gzip’, the adaptation machinery will mark the interface such that
this environment will match the IGZipRequest interface.
This would be an alternative to subclassing, where we would manually
have to set up an event listener that interprets the request
environment and marks the request with the interface.

>>> class IGZipRequest(IRequest):
... """Marker interface for requests for gzipped response."""



Credits
Stefan Eletzhofer <[email protected]> and Malthe Borch
<[email protected]>.



Adaptable HTTP request interfaces
Suppose we want to adapt on requests that have an “http_accept_encoding”
that calls for a gzipped response, we’d set up an interface as
follows:

>>> from repoze.bfg.interfaces import IRequest
>>> IGZipRequest = IRequest({'http_accept_encoding': 'gzip'})


Let’s now craft a request that will match this interface.

>>> class TestRequest(object):
... interface.implements(IRequest)
...
... def __init__(self, environ):
... self.environ = environ

>>> request = TestRequest({'http_accept_encoding': 'compress, gzip'})


At this point, the request has not been prepared for adaptation.

>>> from repoze.bfg.events import NewRequest
>>> from zope.event import notify
>>> notify(NewRequest(request))


We expect the request to implement the IGZipRequest interface.

>>> IGZipRequest.providedBy(request)
True


To get more flexibility, we can supply a match function:

>>> IAlternativeGZipRequest = IRequest(
... {'http_accept_encoding': lambda value: 'gzip' in value})

>>> notify(NewRequest(request))
>>> IAlternativeGZipRequest.providedBy(request)
True


Suppose now we’d also like to support requests for documents in
German.

>>> IGermanLanguageRequest = IRequest({'http_accept_language': 'de'})


We’ll create a new request, which, besides asking a gzipped response,
also asks for the content in German.

>>> request = TestRequest(
... {'http_accept_encoding': 'compress, gzip', 'http_accept_language': 'de'})

>>> notify(NewRequest(request))


Verify that the request provides the adapted interfaces.

>>> IGermanLanguageRequest.providedBy(request)
True

>>> IGZipRequest.providedBy(request)
True


Now, as you would expect, we can adapt a request interface that
combines these two environments.

>>> IZippedGerman = IRequest(
... {'http_accept_encoding': 'gzip', 'http_accept_language': 'de'})
>>> notify(NewRequest(request))

>>> IZippedGerman.providedBy(request)
True


Note that this interface extends the two interfaces that were created
for each of the environment pairs of it.

>>> IZippedGerman.isOrExtends(IGermanLanguageRequest)
True

>>> IZippedGerman.isOrExtends(IGZipRequest)
True


Let’s try a request that doesn’t match.

>>> IZippedFrench = IRequest(
... {'http_accept_encoding': 'gzip', 'http_accept_language': 'fr'})
>>> notify(NewRequest(request))

>>> IZippedFrench.providedBy(request)
False


Adapted requests are global with respect to the environment:

>>> IRequest({'http_accept_encoding': 'gzip'}) is IRequest({'http_accept_encoding': 'gzip'})
True



Pickle-support
The adapted interface are created dynamically and would therefore not
be locatable by the pickle module. To remedy this, an import hook
is added on package initialization.
(The repoze.bfg packages pickles configuration actions in order to
improve startup time, and therefore it’s important that the adapted
interfaces are pickable.)

>>> from pickle import dumps, loads
>>> p = dumps(IGZipRequest)


Now, we’ll pretend that we the repoze.bfg.httprequest.interfaces has
not yet been imported. This will make pickle import it when we load
back the pickle.

>>> import sys
>>> del sys.modules['repozehttprequestinterfaces']


We’ll reinitialize the interfaces module.

>>> loads(p)
<IHTTPRequest http_accept_encoding=gzip>