2f6285e42a
Middleware components superseded global hooks in version 0.3 of the
framework. By now, developers should have had enough time to migrate
away from the deprecated feature. If not, they can continue using 0.3
until they are able to migrate.
BREAKING CHANGE: falcon.API no longer accepts `before` and `after`
kwargs to specify global hooks. Applications should migrate
any logic contained in global hooks to reside in middleware
components instead.
Old:
def do_something(req, resp, resource, params):
pass
app = falcon.API(before=[do_something])
New:
class ExampleMiddlewareComponent(object):
def process_resource(self, req, resp, resource):
pass
Closes #384
217 lines
7.2 KiB
Python
217 lines
7.2 KiB
Python
# Copyright 2013 by Rackspace Hosting, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import functools
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from functools import wraps
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import inspect
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import six
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from falcon import HTTP_METHODS
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def before(action):
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"""Decorator to execute the given action function *before* the responder.
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Args:
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action (callable): A function of the form
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``func(req, resp, resource, params)``, where `resource` is a
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reference to the resource class instance associated with the
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request, and `params` is a dict of URI Template field names,
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if any, that will be passed into the resource responder as
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kwargs.
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Note:
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Hooks may inject extra params as needed. For example::
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def do_something(req, resp, resource, params):
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try:
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params['id'] = int(params['id'])
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except ValueError:
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raise falcon.HTTPBadRequest('Invalid ID',
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'ID was not valid.')
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params['answer'] = 42
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"""
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def _before(responder_or_resource):
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if isinstance(responder_or_resource, six.class_types):
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resource = responder_or_resource
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for method in HTTP_METHODS:
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responder_name = 'on_' + method.lower()
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try:
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responder = getattr(resource, responder_name)
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except AttributeError:
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# resource does not implement this method
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pass
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else:
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# Usually expect a method, but any callable will do
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if callable(responder):
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# This pattern is necessary to capture the current
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# value of responder in the do_before_all closure;
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# otherwise, they will capture the same responder
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# variable that is shared between iterations of the
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# for loop, above.
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def let(responder=responder):
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do_before_all = _wrap_with_before(action, responder)
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setattr(resource, responder_name, do_before_all)
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let()
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return resource
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else:
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responder = responder_or_resource
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do_before_one = _wrap_with_before(action, responder)
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return do_before_one
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return _before
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def after(action):
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"""Decorator to execute the given action function *after* the responder.
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Args:
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action (callable): A function of the form
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``func(req, resp, resource)``, where `resource` is a
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reference to the resource class instance associated with the
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request
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"""
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def _after(responder_or_resource):
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if isinstance(responder_or_resource, six.class_types):
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resource = responder_or_resource
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for method in HTTP_METHODS:
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responder_name = 'on_' + method.lower()
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try:
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responder = getattr(resource, responder_name)
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except AttributeError:
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# resource does not implement this method
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pass
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else:
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# Usually expect a method, but any callable will do
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if callable(responder):
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def let(responder=responder):
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do_after_all = _wrap_with_after(action, responder)
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setattr(resource, responder_name, do_after_all)
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let()
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return resource
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else:
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responder = responder_or_resource
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do_after_one = _wrap_with_after(action, responder)
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return do_after_one
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return _after
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# -----------------------------------------------------------------------------
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# Helpers
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# -----------------------------------------------------------------------------
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def _has_resource_arg(action):
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"""Check if the given action function accepts a resource arg."""
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if isinstance(action, functools.partial):
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# NOTE(kgriffs): We special-case this, since versions of
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# Python prior to 3.4 raise an error when trying to get the
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# spec for a partial.
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spec = inspect.getargspec(action.func)
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elif inspect.isroutine(action):
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# NOTE(kgriffs): We have to distinguish between instances of a
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# callable class vs. a routine, since Python versions prior to
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# 3.4 raise an error when trying to get the spec from
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# a callable class instance.
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spec = inspect.getargspec(action)
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else:
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spec = inspect.getargspec(action.__call__)
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return 'resource' in spec.args
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def _wrap_with_after(action, responder):
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"""Execute the given action function after a responder method.
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Args:
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action: A function with a signature similar to a resource responder
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method, taking the form ``func(req, resp, resource)``.
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responder: The responder method to wrap.
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"""
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# NOTE(swistakm): create shim before checking what will be actually
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# decorated. This helps to avoid excessive nesting
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if _has_resource_arg(action):
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shim = action
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else:
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# TODO(kgriffs): This decorator does not work on callable
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# classes in Python vesions prior to 3.4.
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#
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# @wraps(action)
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def shim(req, resp, resource):
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action(req, resp)
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@wraps(responder)
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def do_after(self, req, resp, **kwargs):
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responder(self, req, resp, **kwargs)
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shim(req, resp, self)
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return do_after
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def _wrap_with_before(action, responder):
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"""Execute the given action function before a responder method.
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Args:
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action: A function with a similar signature to a resource responder
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method, taking the form ``func(req, resp, resource, params)``.
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responder: The responder method to wrap
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"""
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# NOTE(swistakm): create shim before checking what will be actually
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# decorated. This allows to avoid excessive nesting
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if _has_resource_arg(action):
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shim = action
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else:
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# TODO(kgriffs): This decorator does not work on callable
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# classes in Python vesions prior to 3.4.
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#
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# @wraps(action)
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def shim(req, resp, resource, kwargs):
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# NOTE(kgriffs): Don't have to pass "self" even if has_self,
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# since method is assumed to be bound.
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action(req, resp, kwargs)
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@wraps(responder)
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def do_before(self, req, resp, **kwargs):
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shim(req, resp, self, kwargs)
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responder(self, req, resp, **kwargs)
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return do_before
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