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#!/usr/bin/python
#
# Copyright (C) 2008 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""This module provides a common interface for all HTTP requests.
HttpResponse: Represents the server's response to an HTTP request. Provides
an interface identical to httplib.HTTPResponse which is the response
expected from higher level classes which use HttpClient.request.
GenericHttpClient: Provides an interface (superclass) for an object
responsible for making HTTP requests. Subclasses of this object are
used in AtomService and GDataService to make requests to the server. By
changing the http_client member object, the AtomService is able to make
HTTP requests using different logic (for example, when running on
Google App Engine, the http_client makes requests using the App Engine
urlfetch API).
"""
__author__ = 'api.jscudder (Jeff Scudder)'
import StringIO
USER_AGENT = '%s GData-Python/2.0.2'
class Error(Exception):
pass
class UnparsableUrlObject(Error):
pass
class ContentLengthRequired(Error):
pass
class HttpResponse(object):
def __init__(self, body=None, status=None, reason=None, headers=None):
"""Constructor for an HttpResponse object.
HttpResponse represents the server's response to an HTTP request from
the client. The HttpClient.request method returns a httplib.HTTPResponse
object and this HttpResponse class is designed to mirror the interface
exposed by httplib.HTTPResponse.
Args:
body: A file like object, with a read() method. The body could also
be a string, and the constructor will wrap it so that
HttpResponse.read(self) will return the full string.
status: The HTTP status code as an int. Example: 200, 201, 404.
reason: The HTTP status message which follows the code. Example:
OK, Created, Not Found
headers: A dictionary containing the HTTP headers in the server's
response. A common header in the response is Content-Length.
"""
if body:
if hasattr(body, 'read'):
self._body = body
else:
self._body = StringIO.StringIO(body)
else:
self._body = None
if status is not None:
self.status = int(status)
else:
self.status = None
self.reason = reason
self._headers = headers or {}
def getheader(self, name, default=None):
if name in self._headers:
return self._headers[name]
else:
return default
def read(self, amt=None):
if not amt:
return self._body.read()
else:
return self._body.read(amt)
class GenericHttpClient(object):
debug = False
def __init__(self, http_client, headers=None):
"""
Args:
http_client: An object which provides a request method to make an HTTP
request. The request method in GenericHttpClient performs a
call-through to the contained HTTP client object.
headers: A dictionary containing HTTP headers which should be included
in every HTTP request. Common persistent headers include
'User-Agent'.
"""
self.http_client = http_client
self.headers = headers or {}
def request(self, operation, url, data=None, headers=None):
all_headers = self.headers.copy()
if headers:
all_headers.update(headers)
return self.http_client.request(operation, url, data=data,
headers=all_headers)
def get(self, url, headers=None):
return self.request('GET', url, headers=headers)
def post(self, url, data, headers=None):
return self.request('POST', url, data=data, headers=headers)
def put(self, url, data, headers=None):
return self.request('PUT', url, data=data, headers=headers)
def delete(self, url, headers=None):
return self.request('DELETE', url, headers=headers)
class GenericToken(object):
"""Represents an Authorization token to be added to HTTP requests.
Some Authorization headers included calculated fields (digital
signatures for example) which are based on the parameters of the HTTP
request. Therefore the token is responsible for signing the request
and adding the Authorization header.
"""
def perform_request(self, http_client, operation, url, data=None,
headers=None):
"""For the GenericToken, no Authorization token is set."""
return http_client.request(operation, url, data=data, headers=headers)
def valid_for_scope(self, url):
"""Tells the caller if the token authorizes access to the desired URL.
Since the generic token doesn't add an auth header, it is not valid for
any scope.
"""
return False
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