flask源码笔记：三，app.py模块（7）——Flask的方法（下）
源代码：
@setupmethod
def before_request(self, f):
"""Registers a function to run before each request."""
self.before_request_funcs.setdefault(None, []).append(f)
return f
#定义每个请求前执行的函数的装饰器
@setupmethod
def before_first_request(self, f):
"""Registers a function to be run before the first request to this
instance of the application.
.. versionadded:: 0.8
"""
self.before_first_request_funcs.append(f)
#定义第一个请求前执行的函数的装饰器
@setupmethod
def after_request(self, f):
"""Register a function to be run after each request. Your function
must take one parameter, a :attr:`response_class` object and return
a new response object or the same (see :meth:`process_response`).
As of Flask 0.7 this function might not be executed at the end of the
request in case an unhandled exception occurred.
"""
self.after_request_funcs.setdefault(None, []).append(f)
return f
#定义每次请求后响应前执行的函数的装饰器
@setupmethod
def teardown_request(self, f):
"""Register a function to be run at the end of each request,
regardless of whether there was an exception or not. These functions
are executed when the request context is popped, even if not an
actual request was performed.
Example::
ctx = app.test_request_context()
ctx.push()
...
ctx.pop()
When ``ctx.pop()`` is executed in the above example, the teardown
functions are called just before the request context moves from the
stack of active contexts. This becomes relevant if you are using
such constructs in tests.
Generally teardown functions must take every necessary step to avoid
that they will fail. If they do execute code that might fail they
will have to surround the execution of these code by try/except
statements and log occurring errors.
When a teardown function was called because of a exception it will
be passed an error object.
.. admonition:: Debug Note
In debug mode Flask will not tear down a request on an exception
immediately. Instead if will keep it alive so that the interactive
debugger can still access it. This behavior can be controlled
by the ``PRESERVE_CONTEXT_ON_EXCEPTION`` configuration variable.
"""
self.teardown_request_funcs.setdefault(None, []).append(f)
return f
#这个装饰器下 的函 #数在响应对象构建后被调用。它们不允许修改请求，并且它们的返回值被忽略。如果 #请求过程中出错，那么这个错误会传递给每个函数；否则传递 None 。
@setupmethod
def teardown_appcontext(self, f):
"""Registers a function to be called when the application context
ends. These functions are typically also called when the request
context is popped.
Example::
ctx = app.app_context()
ctx.push()
...
ctx.pop()
When ``ctx.pop()`` is executed in the above example, the teardown
functions are called just before the app context moves from the
stack of active contexts. This becomes relevant if you are using
such constructs in tests.
Since a request context typically also manages an application
context it would also be called when you pop a request context.
When a teardown function was called because of an exception it will
be passed an error object.
.. versionadded:: 0.9
"""
self.teardown_appcontext_funcs.append(f)
return f
#定义当应用程序上下文出现丢失等问题时，应该执行的函数的装饰器
@setupmethod
def context_processor(self, f):
"""Registers a template context processor function."""
self.template_context_processors[None].append(f)
return f
#装饰器，将定义的函数传入到模板环境中
@setupmethod
def url_value_preprocessor(self, f):
"""Registers a function as URL value preprocessor for all view
functions of the application. It's called before the view functions
are called and can modify the url values provided.
"""
self.url_value_preprocessors.setdefault(None, []).append(f)
return f
#保存一系列函数，他们在请求成功匹配并且能够执行针对 URL 值的代码时立即执行。实际上，他们将信息从包含这些值的字 #典当中取出，然后将其放在某个其他的地方:
#@app.url_value_preprocessor
#def pull_lang_code(endpoint, values):
# g.lang_code = values.pop('lang_code', None)
@setupmethod
def url_defaults(self, f):
"""Callback function for URL defaults for all view functions of the
application. It's called with the endpoint and values and should
update the values passed in place.
"""
self.url_default_functions.setdefault(None, []).append(f)
return f
#保存一系列函数，他们在使用url_for函数是自动调用
#@app.url_defaults
#def add_language_code(endpoint, values):
# if 'lang_code' in values or not g.lang_code:
# return
# if app.url_map.is_endpoint_expecting(endpoint, 'lang_code'):
# values['lang_code'] = g.lang_code
#@app.url_value_preprocessor和@app.url_defaults配合使用，可以一次处理url规则，从而对所有url生 #效。例如需要检查url中的语言规则的例子。先用@app.url_value_preprocessor获取并剔除该参数 #lang_code，然后在@app.url_defaults中将其插入到参数列表中。
def handle_http_exception(self, e):
"""Handles an HTTP exception. By default this will invoke the
registered error handlers and fall back to returning the
exception as response.
.. versionadded:: 0.3
"""
handlers = self.error_handler_spec.get(request.blueprint)
# Proxy exceptions don't have error codes. We want to always return
# those unchanged as errors
if e.code is None:
return e
if handlers and e.code in handlers:
handler = handlers[e.code]
else:
handler = self.error_handler_spec[None].get(e.code)
if handler is None:
return e
return handler(e)
#http异常处理函数
def trap_http_exception(self, e):
"""Checks if an HTTP exception should be trapped or not. By default
this will return `False` for all exceptions except for a bad request
key error if ``TRAP_BAD_REQUEST_ERRORS`` is set to `True`. It
also returns `True` if ``TRAP_HTTP_EXCEPTIONS`` is set to `True`.
This is called for all HTTP exceptions raised by a view function.
If it returns `True` for any exception the error handler for this
exception is not called and it shows up as regular exception in the
traceback. This is helpful for debugging implicitly raised HTTP
exceptions.
.. versionadded:: 0.8
"""
if self.config['TRAP_HTTP_EXCEPTIONS']:
return True
if self.config['TRAP_BAD_REQUEST_ERRORS']:
return isinstance(e, BadRequest)
return False
#校验是否对http异常进行抓取
def handle_user_exception(self, e):
"""This method is called whenever an exception occurs that should be
handled. A special case are
:class:`~werkzeug.exception.HTTPException`\s which are forwarded by
this function to the :meth:`handle_http_exception` method. This
function will either return a response value or reraise the
exception with the same traceback.
.. versionadded:: 0.7
"""
exc_type, exc_value, tb = sys.exc_info()
assert exc_value is e
# ensure not to trash sys.exc_info() at that point in case someone
# wants the traceback preserved in handle_http_exception. Of course
# we cannot prevent users from trashing it themselves in a custom
# trap_http_exception method so that's their fault then.
if isinstance(e, HTTPException) and not self.trap_http_exception(e):
return self.handle_http_exception(e)
blueprint_handlers = ()
handlers = self.error_handler_spec.get(request.blueprint)
if handlers is not None:
blueprint_handlers = handlers.get(None, ())
app_handlers = self.error_handler_spec[None].get(None, ())
for typecheck, handler in chain(blueprint_handlers, app_handlers):
if isinstance(e, typecheck):
return handler(e)
reraise(exc_type, exc_value, tb)
#处理用户错误的函数
def handle_exception(self, e):
"""Default exception handling that kicks in when an exception
occurs that is not caught. In debug mode the exception will
be re-raised immediately, otherwise it is logged and the handler
for a 500 internal server error is used. If no such handler
exists, a default 500 internal server error message is displayed.
.. versionadded:: 0.3
"""
exc_type, exc_value, tb = sys.exc_info()
got_request_exception.send(self, exception=e)
handler = self.error_handler_spec[None].get(500)
if self.propagate_exceptions:
# if we want to repropagate the exception, we can attempt to
# raise it with the whole traceback in case we can do that
# (the function was actually called from the except part)
# otherwise, we just raise the error again
if exc_value is e:
reraise(exc_type, exc_value, tb)
else:
raise e
self.log_exception((exc_type, exc_value, tb))
if handler is None:
return InternalServerError()
return handler(e)
#处理服务器错误的函数
def log_exception(self, exc_info):
"""Logs an exception. This is called by :meth:`handle_exception`
if debugging is disabled and right before the handler is called.
The default implementation logs the exception as error on the
:attr:`logger`.
.. versionadded:: 0.8
"""
self.logger.error('Exception on %s [%s]' % (
request.path,
request.method
), exc_info=exc_info)
#对异常添加日志记录
def raise_routing_exception(self, request):
"""Exceptions that are recording during routing are reraised with
this method. During debug we are not reraising redirect requests
for non ``GET``, ``HEAD``, or ``OPTIONS`` requests and we're raising
a different error instead to help debug situations.
:internal:
"""
if not self.debug \
or not isinstance(request.routing_exception, RequestRedirect) \
or request.method in ('GET', 'HEAD', 'OPTIONS'):
raise request.routing_exception
from .debughelpers import FormDataRoutingRedirect
raise FormDataRoutingRedirect(request)
#引发路由异常的函数
def dispatch_request(self):
"""Does the request dispatching. Matches the URL and returns the
return value of the view or error handler. This does not have to
be a response object. In order to convert the return value to a
proper response object, call :func:`make_response`.
.. versionchanged:: 0.7
This no longer does the exception handling, this code was
moved to the new :meth:`full_dispatch_request`.
"""
req = _request_ctx_stack.top.request
if req.routing_exception is not None:
self.raise_routing_exception(req)
rule = req.url_rule
# if we provide automatic options for this URL and the
# request came with the OPTIONS method, reply automatically
if getattr(rule, 'provide_automatic_options', False) \
and req.method == 'OPTIONS':
return self.make_default_options_response()
# otherwise dispatch to the handler for that endpoint
return self.view_functions[rule.endpoint](**req.view_args)
#获取请求之后，进行调度的函数，核心函数之一
def full_dispatch_request(self):
"""Dispatches the request and on top of that performs request
pre and postprocessing as well as HTTP exception catching and
error handling.
.. versionadded:: 0.7
"""
self.try_trigger_before_first_request_functions()
try:
request_started.send(self)
rv = self.preprocess_request()
if rv is None:
rv = self.dispatch_request()
except Exception as e:
rv = self.handle_user_exception(e)
response = self.make_response(rv)
response = self.process_response(response)
request_finished.send(self, response=response)
return response
#整个请求的完整调度过程函数，核心函数之一
def try_trigger_before_first_request_functions(self):
"""Called before each request and will ensure that it triggers
the :attr:`before_first_request_funcs` and only exactly once per
application instance (which means process usually).
:internal:
"""
if self._got_first_request:
return
with self._before_request_lock:
if self._got_first_request:
return
self._got_first_request = True
for func in self.before_first_request_funcs:
func()
#触发第一个请求时的执行的函数（包含执行诸多的定义的第一个请求之前需要执行的函数）
def make_default_options_response(self):
"""This method is called to create the default `OPTIONS` response.
This can be changed through subclassing to change the default
behavior of `OPTIONS` responses.
.. versionadded:: 0.7
"""
adapter = _request_ctx_stack.top.url_adapter
if hasattr(adapter, 'allowed_methods'):
methods = adapter.allowed_methods()
else:
# fallback for Werkzeug < 0.7
methods = []
try:
adapter.match(method='--')
except MethodNotAllowed as e:
methods = e.valid_methods
except HTTPException as e:
pass
rv = self.response_class()
rv.allow.update(methods)
return rv
#创建默认的option方法的响应的函数
def should_ignore_error(self, error):
"""This is called to figure out if an error should be ignored
or not as far as the teardown system is concerned. If this
function returns `True` then the teardown handlers will not be
passed the error.
.. versionadded:: 0.10
"""
return False
#类似一个只读的属性，只返回False,不能忽略错误
def make_response(self, rv):
"""Converts the return value from a view function to a real
response object that is an instance of :attr:`response_class`.
The following types are allowed for `rv`:
.. tabularcolumns:: |p{3.5cm}|p{9.5cm}|
======================= ===========================================
:attr:`response_class` the object is returned unchanged
:class:`str` a response object is created with the
string as body
:class:`unicode` a response object is created with the
string encoded to utf-8 as body
a WSGI function the function is called as WSGI application
and buffered as response object
:class:`tuple` A tuple in the form ``(response, status,
headers)`` where `response` is any of the
types defined here, `status` is a string
or an integer and `headers` is a list of
a dictionary with header values.
======================= ===========================================
:param rv: the return value from the view function
.. versionchanged:: 0.9
Previously a tuple was interpreted as the arguments for the
response object.
"""
status = headers = None
if isinstance(rv, tuple):
rv, status, headers = rv + (None,) * (3 - len(rv))
if rv is None:
raise ValueError('View function did not return a response')
if not isinstance(rv, self.response_class):
# When we create a response object directly, we let the constructor
# set the headers and status. We do this because there can be
# some extra logic involved when creating these objects with
# specific values (like default content type selection).
if isinstance(rv, (text_type, bytes, bytearray)):
rv = self.response_class(rv, headers=headers, status=status)
headers = status = None
else:
rv = self.response_class.force_type(rv, request.environ)
if status is not None:
if isinstance(status, string_types):
rv.status = status
else:
rv.status_code = status
if headers:
rv.headers.extend(headers)
return rv
#制作响应的函数，核心函数之一
def create_url_adapter(self, request):
"""Creates a URL adapter for the given request. The URL adapter
is created at a point where the request context is not yet set up
so the request is passed explicitly.
.. versionadded:: 0.6
.. versionchanged:: 0.9
This can now also be called without a request object when the
URL adapter is created for the application context.
"""
if request is not None:
return self.url_map.bind_to_environ(request.environ,
server_name=self.config['SERVER_NAME'])
# We need at the very least the server name to be set for this
# to work.
if self.config['SERVER_NAME'] is not None:
return self.url_map.bind(
self.config['SERVER_NAME'],
script_name=self.config['APPLICATION_ROOT'] or '/',
url_scheme=self.config['PREFERRED_URL_SCHEME'])
#创建以配置参数SERVER_NAME为key，其后值为value的域名为访问应用（根）域名的唯一方法
def inject_url_defaults(self, endpoint, values):
"""Injects the URL defaults for the given endpoint directly into
the values dictionary passed. This is used internally and
automatically called on URL building.
.. versionadded:: 0.7
"""
funcs = self.url_default_functions.get(None, ())
if '.' in endpoint:
bp = endpoint.rsplit('.', 1)[0]
funcs = chain(funcs, self.url_default_functions.get(bp, ()))
for func in funcs:
func(endpoint, values)
#注入已定义的url_defaults装饰器下的函数
def handle_url_build_error(self, error, endpoint, values):
"""Handle :class:`~werkzeug.routing.BuildError` on :meth:`url_for`.
"""
exc_type, exc_value, tb = sys.exc_info()
for handler in self.url_build_error_handlers:
try:
rv = handler(error, endpoint, values)
if rv is not None:
return rv
except BuildError as error:
pass
# At this point we want to reraise the exception. If the error is
# still the same one we can reraise it with the original traceback,
# otherwise we raise it from here.
if error is exc_value:
reraise(exc_type, exc_value, tb)
raise error
#处理url build错误
def preprocess_request(self):
"""Called before the actual request dispatching and will
call every as :meth:`before_request` decorated function.
If any of these function returns a value it's handled as
if it was the return value from the view and further
request handling is stopped.
This also triggers the :meth:`url_value_processor` functions before
the actual :meth:`before_request` functions are called.
"""
bp = _request_ctx_stack.top.request.blueprint
funcs = self.url_value_preprocessors.get(None, ())
if bp is not None and bp in self.url_value_preprocessors:
funcs = chain(funcs, self.url_value_preprocessors[bp])
for func in funcs:
func(request.endpoint, request.view_args)
funcs = self.before_request_funcs.get(None, ())
if bp is not None and bp in self.before_request_funcs:
funcs = chain(funcs, self.before_request_funcs[bp])
for func in funcs:
rv = func()
if rv is not None:
return rv
#预处理请求的函数，核心函数之一，先处理@app.url_value_preprocessor装饰器的函数，
#再处理@app.before_request装饰器的函数
def process_response(self, response):
"""Can be overridden in order to modify the response object
before it's sent to the WSGI server. By default this will
call all the :meth:`after_request` decorated functions.
.. versionchanged:: 0.5
As of Flask 0.5 the functions registered for after request
execution are called in reverse order of registration.
:param response: a :attr:`response_class` object.
:return: a new response object or the same, has to be an
instance of :attr:`response_class`.
"""
ctx = _request_ctx_stack.top
bp = ctx.request.blueprint
funcs = ctx._after_request_functions
if bp is not None and bp in self.after_request_funcs:
funcs = chain(funcs, reversed(self.after_request_funcs[bp]))
if None in self.after_request_funcs:
funcs = chain(funcs, reversed(self.after_request_funcs[None]))
for handler in funcs:
response = handler(response)
if not self.session_interface.is_null_session(ctx.session):
self.save_session(ctx.session, response)
return response
#处理响应，核心函数之一，处理@app.after_request装饰器的函数
def do_teardown_request(self, exc=None):
"""Called after the actual request dispatching and will
call every as :meth:`teardown_request` decorated function. This is
not actually called by the :class:`Flask` object itself but is always
triggered when the request context is popped. That way we have a
tighter control over certain resources under testing environments.
.. versionchanged:: 0.9
Added the `exc` argument. Previously this was always using the
current exception information.
"""
if exc is None:
exc = sys.exc_info()[1]
funcs = reversed(self.teardown_request_funcs.get(None, ()))
bp = _request_ctx_stack.top.request.blueprint
if bp is not None and bp in self.teardown_request_funcs:
funcs = chain(funcs, reversed(self.teardown_request_funcs[bp]))
for func in funcs:
rv = func(exc)
request_tearing_down.send(self, exc=exc)
#执行app.teardown_request_funcs字典中的函数
def do_teardown_appcontext(self, exc=None):
"""Called when an application context is popped. This works pretty
much the same as :meth:`do_teardown_request` but for the application
context.
.. versionadded:: 0.9
"""
if exc is None:
exc = sys.exc_info()[1]
for func in reversed(self.teardown_appcontext_funcs):
func(exc)
appcontext_tearing_down.send(self, exc=exc)
#执行app.teardown_appcontext_funcs字典中的函数
def app_context(self):
"""Binds the application only. For as long as the application is bound
to the current context the :data:`flask.current_app` points to that
application. An application context is automatically created when a
request context is pushed if necessary.
Example usage::
with app.app_context():
...
.. versionadded:: 0.9
"""
return AppContext(self)
#返回应用程序上下文
def request_context(self, environ):
"""Creates a :class:`~flask.ctx.RequestContext` from the given
environment and binds it to the current context. This must be used in
combination with the `with` statement because the request is only bound
to the current context for the duration of the `with` block.
Example usage::
with app.request_context(environ):
do_something_with(request)
The object returned can also be used without the `with` statement
which is useful for working in the shell. The example above is
doing exactly the same as this code::
ctx = app.request_context(environ)
ctx.push()
try:
do_something_with(request)
finally:
ctx.pop()
.. versionchanged:: 0.3
Added support for non-with statement usage and `with` statement
is now passed the ctx object.
:param environ: a WSGI environment
"""
return RequestContext(self, environ)
#返回请求上下文
def test_request_context(self, *args, **kwargs):
"""Creates a WSGI environment from the given values (see
:func:`werkzeug.test.EnvironBuilder` for more information, this
function accepts the same arguments).
"""
from flask.testing import make_test_environ_builder
builder = make_test_environ_builder(self, *args, **kwargs)
try:
return self.request_context(builder.get_environ())
finally:
builder.close()
#尝试返回测试请求的上下文
def wsgi_app(self, environ, start_response):
"""The actual WSGI application. This is not implemented in
`__call__` so that middlewares can be applied without losing a
reference to the class. So instead of doing this::
app = MyMiddleware(app)
It's a better idea to do this instead::
app.wsgi_app = MyMiddleware(app.wsgi_app)
Then you still have the original application object around and
can continue to call methods on it.
.. versionchanged:: 0.7
The behavior of the before and after request callbacks was changed
under error conditions and a new callback was added that will
always execute at the end of the request, independent on if an
error occurred or not. See :ref:`callbacks-and-errors`.
:param environ: a WSGI environment
:param start_response: a callable accepting a status code,
a list of headers and an optional
exception context to start the response
"""
ctx = self.request_context(environ)
ctx.push()
error = None
try:
try:
response = self.full_dispatch_request()
except Exception as e:
error = e
response = self.make_response(self.handle_exception(e))
return response(environ, start_response)
finally:
if self.should_ignore_error(error):
error = None
ctx.auto_pop(error)
#创建一个wsgi应用的函数，主要用于将app用于正式部署
@property
def modules(self):
from warnings import warn
warn(DeprecationWarning('Flask.modules is deprecated, use '
'Flask.blueprints instead'), stacklevel=2)
return self.blueprints
#弃用属性modules，发出警告并返回blueprints
def __call__(self, environ, start_response):
"""Shortcut for :attr:`wsgi_app`."""
return self.wsgi_app(environ, start_response)
#当实例当做函数使用时，调用的实际是wsgi_app函数
def __repr__(self):
return '<%s %r>' % (
self.__class__.__name__,
self.name,
)
#自身的在python shell中的显示
@setupmethod
def before_request(self, f):
"""Registers a function to run before each request."""
self.before_request_funcs.setdefault(None, []).append(f)
return f
#定义每个请求前执行的函数的装饰器
@setupmethod
def before_first_request(self, f):
"""Registers a function to be run before the first request to this
instance of the application.
.. versionadded:: 0.8
"""
self.before_first_request_funcs.append(f)
#定义第一个请求前执行的函数的装饰器
@setupmethod
def after_request(self, f):
"""Register a function to be run after each request. Your function
must take one parameter, a :attr:`response_class` object and return
a new response object or the same (see :meth:`process_response`).
As of Flask 0.7 this function might not be executed at the end of the
request in case an unhandled exception occurred.
"""
self.after_request_funcs.setdefault(None, []).append(f)
return f
#定义每次请求后响应前执行的函数的装饰器
@setupmethod
def teardown_request(self, f):
"""Register a function to be run at the end of each request,
regardless of whether there was an exception or not. These functions
are executed when the request context is popped, even if not an
actual request was performed.
Example::
ctx = app.test_request_context()
ctx.push()
...
ctx.pop()
When ``ctx.pop()`` is executed in the above example, the teardown
functions are called just before the request context moves from the
stack of active contexts. This becomes relevant if you are using
such constructs in tests.
Generally teardown functions must take every necessary step to avoid
that they will fail. If they do execute code that might fail they
will have to surround the execution of these code by try/except
statements and log occurring errors.
When a teardown function was called because of a exception it will
be passed an error object.
.. admonition:: Debug Note
In debug mode Flask will not tear down a request on an exception
immediately. Instead if will keep it alive so that the interactive
debugger can still access it. This behavior can be controlled
by the ``PRESERVE_CONTEXT_ON_EXCEPTION`` configuration variable.
"""
self.teardown_request_funcs.setdefault(None, []).append(f)
return f
#这个装饰器下 的函 #数在响应对象构建后被调用。它们不允许修改请求，并且它们的返回值被忽略。如果 #请求过程中出错，那么这个错误会传递给每个函数；否则传递 None 。
@setupmethod
def teardown_appcontext(self, f):
"""Registers a function to be called when the application context
ends. These functions are typically also called when the request
context is popped.
Example::
ctx = app.app_context()
ctx.push()
...
ctx.pop()
When ``ctx.pop()`` is executed in the above example, the teardown
functions are called just before the app context moves from the
stack of active contexts. This becomes relevant if you are using
such constructs in tests.
Since a request context typically also manages an application
context it would also be called when you pop a request context.
When a teardown function was called because of an exception it will
be passed an error object.
.. versionadded:: 0.9
"""
self.teardown_appcontext_funcs.append(f)
return f
#定义当应用程序上下文出现丢失等问题时，应该执行的函数的装饰器
@setupmethod
def context_processor(self, f):
"""Registers a template context processor function."""
self.template_context_processors[None].append(f)
return f
#装饰器，将定义的函数传入到模板环境中
@setupmethod
def url_value_preprocessor(self, f):
"""Registers a function as URL value preprocessor for all view
functions of the application. It's called before the view functions
are called and can modify the url values provided.
"""
self.url_value_preprocessors.setdefault(None, []).append(f)
return f
#保存一系列函数，他们在请求成功匹配并且能够执行针对 URL 值的代码时立即执行。实际上，他们将信息从包含这些值的字 #典当中取出，然后将其放在某个其他的地方:
#@app.url_value_preprocessor
#def pull_lang_code(endpoint, values):
# g.lang_code = values.pop('lang_code', None)
@setupmethod
def url_defaults(self, f):
"""Callback function for URL defaults for all view functions of the
application. It's called with the endpoint and values and should
update the values passed in place.
"""
self.url_default_functions.setdefault(None, []).append(f)
return f
#保存一系列函数，他们在使用url_for函数是自动调用
#@app.url_defaults
#def add_language_code(endpoint, values):
# if 'lang_code' in values or not g.lang_code:
# return
# if app.url_map.is_endpoint_expecting(endpoint, 'lang_code'):
# values['lang_code'] = g.lang_code
#@app.url_value_preprocessor和@app.url_defaults配合使用，可以一次处理url规则，从而对所有url生 #效。例如需要检查url中的语言规则的例子。先用@app.url_value_preprocessor获取并剔除该参数 #lang_code，然后在@app.url_defaults中将其插入到参数列表中。
def handle_http_exception(self, e):
"""Handles an HTTP exception. By default this will invoke the
registered error handlers and fall back to returning the
exception as response.
.. versionadded:: 0.3
"""
handlers = self.error_handler_spec.get(request.blueprint)
# Proxy exceptions don't have error codes. We want to always return
# those unchanged as errors
if e.code is None:
return e
if handlers and e.code in handlers:
handler = handlers[e.code]
else:
handler = self.error_handler_spec[None].get(e.code)
if handler is None:
return e
return handler(e)
#http异常处理函数
def trap_http_exception(self, e):
"""Checks if an HTTP exception should be trapped or not. By default
this will return `False` for all exceptions except for a bad request
key error if ``TRAP_BAD_REQUEST_ERRORS`` is set to `True`. It
also returns `True` if ``TRAP_HTTP_EXCEPTIONS`` is set to `True`.
This is called for all HTTP exceptions raised by a view function.
If it returns `True` for any exception the error handler for this
exception is not called and it shows up as regular exception in the
traceback. This is helpful for debugging implicitly raised HTTP
exceptions.
.. versionadded:: 0.8
"""
if self.config['TRAP_HTTP_EXCEPTIONS']:
return True
if self.config['TRAP_BAD_REQUEST_ERRORS']:
return isinstance(e, BadRequest)
return False
#校验是否对http异常进行抓取
def handle_user_exception(self, e):
"""This method is called whenever an exception occurs that should be
handled. A special case are
:class:`~werkzeug.exception.HTTPException`\s which are forwarded by
this function to the :meth:`handle_http_exception` method. This
function will either return a response value or reraise the
exception with the same traceback.
.. versionadded:: 0.7
"""
exc_type, exc_value, tb = sys.exc_info()
assert exc_value is e
# ensure not to trash sys.exc_info() at that point in case someone
# wants the traceback preserved in handle_http_exception. Of course
# we cannot prevent users from trashing it themselves in a custom
# trap_http_exception method so that's their fault then.
if isinstance(e, HTTPException) and not self.trap_http_exception(e):
return self.handle_http_exception(e)
blueprint_handlers = ()
handlers = self.error_handler_spec.get(request.blueprint)
if handlers is not None:
blueprint_handlers = handlers.get(None, ())
app_handlers = self.error_handler_spec[None].get(None, ())
for typecheck, handler in chain(blueprint_handlers, app_handlers):
if isinstance(e, typecheck):
return handler(e)
reraise(exc_type, exc_value, tb)
#处理用户错误的函数
def handle_exception(self, e):
"""Default exception handling that kicks in when an exception
occurs that is not caught. In debug mode the exception will
be re-raised immediately, otherwise it is logged and the handler
for a 500 internal server error is used. If no such handler
exists, a default 500 internal server error message is displayed.
.. versionadded:: 0.3
"""
exc_type, exc_value, tb = sys.exc_info()
got_request_exception.send(self, exception=e)
handler = self.error_handler_spec[None].get(500)
if self.propagate_exceptions:
# if we want to repropagate the exception, we can attempt to
# raise it with the whole traceback in case we can do that
# (the function was actually called from the except part)
# otherwise, we just raise the error again
if exc_value is e:
reraise(exc_type, exc_value, tb)
else:
raise e
self.log_exception((exc_type, exc_value, tb))
if handler is None:
return InternalServerError()
return handler(e)
#处理服务器错误的函数
def log_exception(self, exc_info):
"""Logs an exception. This is called by :meth:`handle_exception`
if debugging is disabled and right before the handler is called.
The default implementation logs the exception as error on the
:attr:`logger`.
.. versionadded:: 0.8
"""
self.logger.error('Exception on %s [%s]' % (
request.path,
request.method
), exc_info=exc_info)
#对异常添加日志记录
def raise_routing_exception(self, request):
"""Exceptions that are recording during routing are reraised with
this method. During debug we are not reraising redirect requests
for non ``GET``, ``HEAD``, or ``OPTIONS`` requests and we're raising
a different error instead to help debug situations.
:internal:
"""
if not self.debug \
or not isinstance(request.routing_exception, RequestRedirect) \
or request.method in ('GET', 'HEAD', 'OPTIONS'):
raise request.routing_exception
from .debughelpers import FormDataRoutingRedirect
raise FormDataRoutingRedirect(request)
#引发路由异常的函数
def dispatch_request(self):
"""Does the request dispatching. Matches the URL and returns the
return value of the view or error handler. This does not have to
be a response object. In order to convert the return value to a
proper response object, call :func:`make_response`.
.. versionchanged:: 0.7
This no longer does the exception handling, this code was
moved to the new :meth:`full_dispatch_request`.
"""
req = _request_ctx_stack.top.request
if req.routing_exception is not None:
self.raise_routing_exception(req)
rule = req.url_rule
# if we provide automatic options for this URL and the
# request came with the OPTIONS method, reply automatically
if getattr(rule, 'provide_automatic_options', False) \
and req.method == 'OPTIONS':
return self.make_default_options_response()
# otherwise dispatch to the handler for that endpoint
return self.view_functions[rule.endpoint](**req.view_args)
#获取请求之后，进行调度的函数，核心函数之一
def full_dispatch_request(self):
"""Dispatches the request and on top of that performs request
pre and postprocessing as well as HTTP exception catching and
error handling.
.. versionadded:: 0.7
"""
self.try_trigger_before_first_request_functions()
try:
request_started.send(self)
rv = self.preprocess_request()
if rv is None:
rv = self.dispatch_request()
except Exception as e:
rv = self.handle_user_exception(e)
response = self.make_response(rv)
response = self.process_response(response)
request_finished.send(self, response=response)
return response
#整个请求的完整调度过程函数，核心函数之一
def try_trigger_before_first_request_functions(self):
"""Called before each request and will ensure that it triggers
the :attr:`before_first_request_funcs` and only exactly once per
application instance (which means process usually).
:internal:
"""
if self._got_first_request:
return
with self._before_request_lock:
if self._got_first_request:
return
self._got_first_request = True
for func in self.before_first_request_funcs:
func()
#触发第一个请求时的执行的函数（包含执行诸多的定义的第一个请求之前需要执行的函数）
def make_default_options_response(self):
"""This method is called to create the default `OPTIONS` response.
This can be changed through subclassing to change the default
behavior of `OPTIONS` responses.
.. versionadded:: 0.7
"""
adapter = _request_ctx_stack.top.url_adapter
if hasattr(adapter, 'allowed_methods'):
methods = adapter.allowed_methods()
else:
# fallback for Werkzeug < 0.7
methods = []
try:
adapter.match(method='--')
except MethodNotAllowed as e:
methods = e.valid_methods
except HTTPException as e:
pass
rv = self.response_class()
rv.allow.update(methods)
return rv
#创建默认的option方法的响应的函数
def should_ignore_error(self, error):
"""This is called to figure out if an error should be ignored
or not as far as the teardown system is concerned. If this
function returns `True` then the teardown handlers will not be
passed the error.
.. versionadded:: 0.10
"""
return False
#类似一个只读的属性，只返回False,不能忽略错误
def make_response(self, rv):
"""Converts the return value from a view function to a real
response object that is an instance of :attr:`response_class`.
The following types are allowed for `rv`:
.. tabularcolumns:: |p{3.5cm}|p{9.5cm}|
======================= ===========================================
:attr:`response_class` the object is returned unchanged
:class:`str` a response object is created with the
string as body
:class:`unicode` a response object is created with the
string encoded to utf-8 as body
a WSGI function the function is called as WSGI application
and buffered as response object
:class:`tuple` A tuple in the form ``(response, status,
headers)`` where `response` is any of the
types defined here, `status` is a string
or an integer and `headers` is a list of
a dictionary with header values.
======================= ===========================================
:param rv: the return value from the view function
.. versionchanged:: 0.9
Previously a tuple was interpreted as the arguments for the
response object.
"""
status = headers = None
if isinstance(rv, tuple):
rv, status, headers = rv + (None,) * (3 - len(rv))
if rv is None:
raise ValueError('View function did not return a response')
if not isinstance(rv, self.response_class):
# When we create a response object directly, we let the constructor
# set the headers and status. We do this because there can be
# some extra logic involved when creating these objects with
# specific values (like default content type selection).
if isinstance(rv, (text_type, bytes, bytearray)):
rv = self.response_class(rv, headers=headers, status=status)
headers = status = None
else:
rv = self.response_class.force_type(rv, request.environ)
if status is not None:
if isinstance(status, string_types):
rv.status = status
else:
rv.status_code = status
if headers:
rv.headers.extend(headers)
return rv
#制作响应的函数，核心函数之一
def create_url_adapter(self, request):
"""Creates a URL adapter for the given request. The URL adapter
is created at a point where the request context is not yet set up
so the request is passed explicitly.
.. versionadded:: 0.6
.. versionchanged:: 0.9
This can now also be called without a request object when the
URL adapter is created for the application context.
"""
if request is not None:
return self.url_map.bind_to_environ(request.environ,
server_name=self.config['SERVER_NAME'])
# We need at the very least the server name to be set for this
# to work.
if self.config['SERVER_NAME'] is not None:
return self.url_map.bind(
self.config['SERVER_NAME'],
script_name=self.config['APPLICATION_ROOT'] or '/',
url_scheme=self.config['PREFERRED_URL_SCHEME'])
#创建以配置参数SERVER_NAME为key，其后值为value的域名为访问应用（根）域名的唯一方法
def inject_url_defaults(self, endpoint, values):
"""Injects the URL defaults for the given endpoint directly into
the values dictionary passed. This is used internally and
automatically called on URL building.
.. versionadded:: 0.7
"""
funcs = self.url_default_functions.get(None, ())
if '.' in endpoint:
bp = endpoint.rsplit('.', 1)[0]
funcs = chain(funcs, self.url_default_functions.get(bp, ()))
for func in funcs:
func(endpoint, values)
#注入已定义的url_defaults装饰器下的函数
def handle_url_build_error(self, error, endpoint, values):
"""Handle :class:`~werkzeug.routing.BuildError` on :meth:`url_for`.
"""
exc_type, exc_value, tb = sys.exc_info()
for handler in self.url_build_error_handlers:
try:
rv = handler(error, endpoint, values)
if rv is not None:
return rv
except BuildError as error:
pass
# At this point we want to reraise the exception. If the error is
# still the same one we can reraise it with the original traceback,
# otherwise we raise it from here.
if error is exc_value:
reraise(exc_type, exc_value, tb)
raise error
#处理url build错误
def preprocess_request(self):
"""Called before the actual request dispatching and will
call every as :meth:`before_request` decorated function.
If any of these function returns a value it's handled as
if it was the return value from the view and further
request handling is stopped.
This also triggers the :meth:`url_value_processor` functions before
the actual :meth:`before_request` functions are called.
"""
bp = _request_ctx_stack.top.request.blueprint
funcs = self.url_value_preprocessors.get(None, ())
if bp is not None and bp in self.url_value_preprocessors:
funcs = chain(funcs, self.url_value_preprocessors[bp])
for func in funcs:
func(request.endpoint, request.view_args)
funcs = self.before_request_funcs.get(None, ())
if bp is not None and bp in self.before_request_funcs:
funcs = chain(funcs, self.before_request_funcs[bp])
for func in funcs:
rv = func()
if rv is not None:
return rv
#预处理请求的函数，核心函数之一，先处理@app.url_value_preprocessor装饰器的函数，
#再处理@app.before_request装饰器的函数
def process_response(self, response):
"""Can be overridden in order to modify the response object
before it's sent to the WSGI server. By default this will
call all the :meth:`after_request` decorated functions.
.. versionchanged:: 0.5
As of Flask 0.5 the functions registered for after request
execution are called in reverse order of registration.
:param response: a :attr:`response_class` object.
:return: a new response object or the same, has to be an
instance of :attr:`response_class`.
"""
ctx = _request_ctx_stack.top
bp = ctx.request.blueprint
funcs = ctx._after_request_functions
if bp is not None and bp in self.after_request_funcs:
funcs = chain(funcs, reversed(self.after_request_funcs[bp]))
if None in self.after_request_funcs:
funcs = chain(funcs, reversed(self.after_request_funcs[None]))
for handler in funcs:
response = handler(response)
if not self.session_interface.is_null_session(ctx.session):
self.save_session(ctx.session, response)
return response
#处理响应，核心函数之一，处理@app.after_request装饰器的函数
def do_teardown_request(self, exc=None):
"""Called after the actual request dispatching and will
call every as :meth:`teardown_request` decorated function. This is
not actually called by the :class:`Flask` object itself but is always
triggered when the request context is popped. That way we have a
tighter control over certain resources under testing environments.
.. versionchanged:: 0.9
Added the `exc` argument. Previously this was always using the
current exception information.
"""
if exc is None:
exc = sys.exc_info()[1]
funcs = reversed(self.teardown_request_funcs.get(None, ()))
bp = _request_ctx_stack.top.request.blueprint
if bp is not None and bp in self.teardown_request_funcs:
funcs = chain(funcs, reversed(self.teardown_request_funcs[bp]))
for func in funcs:
rv = func(exc)
request_tearing_down.send(self, exc=exc)
#执行app.teardown_request_funcs字典中的函数
def do_teardown_appcontext(self, exc=None):
"""Called when an application context is popped. This works pretty
much the same as :meth:`do_teardown_request` but for the application
context.
.. versionadded:: 0.9
"""
if exc is None:
exc = sys.exc_info()[1]
for func in reversed(self.teardown_appcontext_funcs):
func(exc)
appcontext_tearing_down.send(self, exc=exc)
#执行app.teardown_appcontext_funcs字典中的函数
def app_context(self):
"""Binds the application only. For as long as the application is bound
to the current context the :data:`flask.current_app` points to that
application. An application context is automatically created when a
request context is pushed if necessary.
Example usage::
with app.app_context():
...
.. versionadded:: 0.9
"""
return AppContext(self)
#返回应用程序上下文
def request_context(self, environ):
"""Creates a :class:`~flask.ctx.RequestContext` from the given
environment and binds it to the current context. This must be used in
combination with the `with` statement because the request is only bound
to the current context for the duration of the `with` block.
Example usage::
with app.request_context(environ):
do_something_with(request)
The object returned can also be used without the `with` statement
which is useful for working in the shell. The example above is
doing exactly the same as this code::
ctx = app.request_context(environ)
ctx.push()
try:
do_something_with(request)
finally:
ctx.pop()
.. versionchanged:: 0.3
Added support for non-with statement usage and `with` statement
is now passed the ctx object.
:param environ: a WSGI environment
"""
return RequestContext(self, environ)
#返回请求上下文
def test_request_context(self, *args, **kwargs):
"""Creates a WSGI environment from the given values (see
:func:`werkzeug.test.EnvironBuilder` for more information, this
function accepts the same arguments).
"""
from flask.testing import make_test_environ_builder
builder = make_test_environ_builder(self, *args, **kwargs)
try:
return self.request_context(builder.get_environ())
finally:
builder.close()
#尝试返回测试请求的上下文
def wsgi_app(self, environ, start_response):
"""The actual WSGI application. This is not implemented in
`__call__` so that middlewares can be applied without losing a
reference to the class. So instead of doing this::
app = MyMiddleware(app)
It's a better idea to do this instead::
app.wsgi_app = MyMiddleware(app.wsgi_app)
Then you still have the original application object around and
can continue to call methods on it.
.. versionchanged:: 0.7
The behavior of the before and after request callbacks was changed
under error conditions and a new callback was added that will
always execute at the end of the request, independent on if an
error occurred or not. See :ref:`callbacks-and-errors`.
:param environ: a WSGI environment
:param start_response: a callable accepting a status code,
a list of headers and an optional
exception context to start the response
"""
ctx = self.request_context(environ)
ctx.push()
error = None
try:
try:
response = self.full_dispatch_request()
except Exception as e:
error = e
response = self.make_response(self.handle_exception(e))
return response(environ, start_response)
finally:
if self.should_ignore_error(error):
error = None
ctx.auto_pop(error)
#创建一个wsgi应用的函数，主要用于将app用于正式部署
@property
def modules(self):
from warnings import warn
warn(DeprecationWarning('Flask.modules is deprecated, use '
'Flask.blueprints instead'), stacklevel=2)
return self.blueprints
#弃用属性modules，发出警告并返回blueprints
def __call__(self, environ, start_response):
"""Shortcut for :attr:`wsgi_app`."""
return self.wsgi_app(environ, start_response)
#当实例当做函数使用时，调用的实际是wsgi_app函数
def __repr__(self):
return '<%s %r>' % (
self.__class__.__name__,
self.name,
)
#自身的在python shell中的显示