Flask请求上下文源码分析
一、概述
在flask应用程序中：
from flask import Flask app = Flask(__name__) @app.route('/index') def helloWorld(): return 'index' if __name__ == '__main__': app.run()
可以看到通过app.run()来启动程序，在这个函数中，通过：
“”“ ... run_simple(host, port, self, **options) ... """
这个函数实际上就是执行：
## app.__call__() #self是app对象，app()
1、__call__
def __call__(self, environ, start_response): """The WSGI server calls the Flask application object as the WSGI application. This calls :meth:`wsgi_app` which can be wrapped to applying middleware.""" return self.wsgi_app(environ, start_response)
__call__函数中接收了请求所有相关的信息environ，最后返回的是wsgi_app函数。
2、wsgi_app
def wsgi_app(self, environ, start_response): ctx = self.request_context(environ) #将请求相关的数据封装到了RequestContext对象中 error = None try: try: ctx.push() response = self.full_dispatch_request() except Exception as e: error = e response = self.handle_exception(e) except: # noqa: B001 error = sys.exc_info()[1] raise return response(environ, start_response) finally: if self.should_ignore_error(error): error = None ctx.auto_pop(error)
- request_context(environ)
在上面的代码中首先创建了一个ctx对象，这个对象是通过request_context函数来创建的（通过RequestContext类创建，实际上就是对请求数据进行封装）。
- ctx.push()
ctx是RequestContext类的对象，在这个类中push方法中：
def push(self): """ ... _request_ctx_stack.push(self) ... """
实际上执行的是_request_ctx_stack对象（LocalStack类）中的push（_request_ctx_stack.push(self)）方法：
class LocalStack(object): """ ... def push(self, obj): """Pushes a new item to the stack""" rv = getattr(self._local, "stack", None) if rv is None: self._local.stack = rv = [] rv.append(obj) return rv ... """
这里就是将obj（request对象）保存在字典中的列表中，比如：
”“” { 11272：{‘stack’:[obj]} } “”“
3、full_dispatch_request()
在这个函数中，主要就是处理处理flask中的路由映射以及视图函数然后将结果返回给用户。
4、ctx.auto_pop(error)
这句代码是在finally语句中执行的，也就是最后是一定要执行的，在这句代码中。
#最后一定执行的是 rv = _request_ctx_stack.pop()
实际上就是执行LocalStack类中pop方法，就是会将刚刚添加的request对象从那个大字典中移除掉。
class LocalStack: def pop(self): """Removes the topmost item from the stack, will return the old value or `None` if the stack was already empty. """ stack = getattr(self._local, "stack", None) if stack is None: return None elif len(stack) == 1: release_local(self._local) return stack[-1] else: return stack.pop()
所以总结一下就是请求到达flask到最后请求结束总体会经过这么三个阶段：
- 请求到达，将所有请求相关的数据封装到RequestContext对象，然后通过LocalStack对象将其封装到Local对象中
- 处理请求，从Local对象中取出r对应的request对象，然后执行对应的路由和视图函数，将结果进行返回
- 移除请求，将对应的请求request对象从Local对象中进行移除
二、源码分析
（一）Local类
class Local(object): __slots__ = ("__storage__", "__ident_func__") def __init__(self): object.__setattr__(self, "__storage__", {}) object.__setattr__(self, "__ident_func__", get_ident) def __iter__(self): return iter(self.__storage__.items()) def __call__(self, proxy): """Create a proxy for a name.""" return LocalProxy(self, proxy) def __release_local__(self): self.__storage__.pop(self.__ident_func__(), None) def __getattr__(self, name): try: return self.__storage__[self.__ident_func__()][name] except KeyError: raise AttributeError(name) def __setattr__(self, name, value): ident = self.__ident_func__() storage = self.__storage__ try: storage[ident][name] = value except KeyError: storage[ident] = {name: value} def __delattr__(self, name): try: del self.__storage__[self.__ident_func__()][name] except KeyError: raise AttributeError(name)
flask为了支持线程和协程，自定义一个Local类，可以保存多个用户requrst对象，不至于混乱。
class Local(object): __slots__ = ("__storage__", "__ident_func__") def __init__(self): #初始化存储字典、唯一线程（协程id） object.__setattr__(self, "__storage__", {}) object.__setattr__(self, "__ident_func__", get_ident) def __getattr__(self, name): #获取值 try: return self.__storage__[self.__ident_func__()][name] except KeyError: raise AttributeError(name) def __setattr__(self, name, value): #赋值操作 ident = self.__ident_func__() storage = self.__storage__ try: storage[ident][name] = value except KeyError: storage[ident] = {name: value}
（二）Flask类
在应用程序中，使用的就是这个类来创建的app对象。然后执行其run、__call__、wsgi_app方法。在wsgi_app方法中完成请求接收、处理请求以及最后的响应。
class Flask(_PackageBoundObject): """The flask object implements a WSGI application and acts as the central object. It is passed the name of the module or package of the application. Once it is created it will act as a central registry for the view functions, the URL rules, template configuration and much more. The name of the package is used to resolve resources from inside the package or the folder the module is contained in depending on if the package parameter resolves to an actual python package (a folder with an :file:`__init__.py` file inside) or a standard module (just a ``.py`` file). For more information about resource loading, see :func:`open_resource`. Usually you create a :class:`Flask` instance in your main module or in the :file:`__init__.py` file of your package like this:: from flask import Flask app = Flask(__name__) .. admonition:: About the First Parameter The idea of the first parameter is to give Flask an idea of what belongs to your application. This name is used to find resources on the filesystem, can be used by extensions to improve debugging information and a lot more. So it's important what you provide there. If you are using a single module, `__name__` is always the correct value. If you however are using a package, it's usually recommended to hardcode the name of your package there. For example if your application is defined in :file:`yourapplication/app.py` you should create it with one of the two versions below:: app = Flask('yourapplication') app = Flask(__name__.split('.')[0]) Why is that? The application will work even with `__name__`, thanks to how resources are looked up. However it will make debugging more painful. Certain extensions can make assumptions based on the import name of your application. For example the Flask-SQLAlchemy extension will look for the code in your application that triggered an SQL query in debug mode. If the import name is not properly set up, that debugging information is lost. (For example it would only pick up SQL queries in `yourapplication.app` and not `yourapplication.views.frontend`) .. versionadded:: 0.7 The `static_url_path`, `static_folder`, and `template_folder` parameters were added. .. versionadded:: 0.8 The `instance_path` and `instance_relative_config` parameters were added. .. versionadded:: 0.11 The `root_path` parameter was added. .. versionadded:: 1.0 The ``host_matching`` and ``static_host`` parameters were added. .. versionadded:: 1.0 The ``subdomain_matching`` parameter was added. Subdomain matching needs to be enabled manually now. Setting :data:`SERVER_NAME` does not implicitly enable it. :param import_name: the name of the application package :param static_url_path: can be used to specify a different path for the static files on the web. Defaults to the name of the `static_folder` folder. :param static_folder: The folder with static files that is served at ``static_url_path``. Relative to the application ``root_path`` or an absolute path. Defaults to ``'static'``. :param static_host: the host to use when adding the static route. Defaults to None. Required when using ``host_matching=True`` with a ``static_folder`` configured. :param host_matching: set ``url_map.host_matching`` attribute. Defaults to False. :param subdomain_matching: consider the subdomain relative to :data:`SERVER_NAME` when matching routes. Defaults to False. :param template_folder: the folder that contains the templates that should be used by the application. Defaults to ``'templates'`` folder in the root path of the application. :param instance_path: An alternative instance path for the application. By default the folder ``'instance'`` next to the package or module is assumed to be the instance path. :param instance_relative_config: if set to ``True`` relative filenames for loading the config are assumed to be relative to the instance path instead of the application root. :param root_path: Flask by default will automatically calculate the path to the root of the application. In certain situations this cannot be achieved (for instance if the package is a Python 3 namespace package) and needs to be manually defined. """ #: The class that is used for request objects. See :class:`~flask.Request` #: for more information. request_class = Request #: The class that is used for response objects. See #: :class:`~flask.Response` for more information. response_class = Response #: The class that is used for the Jinja environment. #: #: .. versionadded:: 0.11 jinja_environment = Environment #: The class that is used for the :data:`~flask.g` instance. #: #: Example use cases for a custom class: #: #: 1. Store arbitrary attributes on flask.g. #: 2. Add a property for lazy per-request database connectors. #: 3. Return None instead of AttributeError on unexpected attributes. #: 4. Raise exception if an unexpected attr is set, a "controlled" flask.g. #: #: In Flask 0.9 this property was called `request_globals_class` but it #: was changed in 0.10 to :attr:`app_ctx_globals_class` because the #: flask.g object is now application context scoped. #: #: .. versionadded:: 0.10 app_ctx_globals_class = _AppCtxGlobals #: The class that is used for the ``config`` attribute of this app. #: Defaults to :class:`~flask.Config`. #: #: Example use cases for a custom class: #: #: 1. Default values for certain config options. #: 2. Access to config values through attributes in addition to keys. #: #: .. versionadded:: 0.11 config_class = Config #: The testing flag. Set this to ``True`` to enable the test mode of #: Flask extensions (and in the future probably also Flask itself). #: For example this might activate test helpers that have an #: additional runtime cost which should not be enabled by default. #: #: If this is enabled and PROPAGATE_EXCEPTIONS is not changed from the #: default it's implicitly enabled. #: #: This attribute can also be configured from the config with the #: ``TESTING`` configuration key. Defaults to ``False``. testing = ConfigAttribute("TESTING") #: If a secret key is set, cryptographic components can use this to #: sign cookies and other things. Set this to a complex random value #: when you want to use the secure cookie for instance. #: #: This attribute can also be configured from the config with the #: :data:`SECRET_KEY` configuration key. Defaults to ``None``. secret_key = ConfigAttribute("SECRET_KEY") #: The secure cookie uses this for the name of the session cookie. #: #: This attribute can also be configured from the config with the #: ``SESSION_COOKIE_NAME`` configuration key. Defaults to ``'session'`` session_cookie_name = ConfigAttribute("SESSION_COOKIE_NAME") #: A :class:`~datetime.timedelta` which is used to set the expiration #: date of a permanent session. The default is 31 days which makes a #: permanent session survive for roughly one month. #: #: This attribute can also be configured from the config with the #: ``PERMANENT_SESSION_LIFETIME`` configuration key. Defaults to #: ``timedelta(days=31)`` permanent_session_lifetime = ConfigAttribute( "PERMANENT_SESSION_LIFETIME", get_converter=_make_timedelta ) #: A :class:`~datetime.timedelta` which is used as default cache_timeout #: for the :func:`send_file` functions. The default is 12 hours. #: #: This attribute can also be configured from the config with the #: ``SEND_FILE_MAX_AGE_DEFAULT`` configuration key. This configuration #: variable can also be set with an integer value used as seconds. #: Defaults to ``timedelta(hours=12)`` send_file_max_age_default = ConfigAttribute( "SEND_FILE_MAX_AGE_DEFAULT", get_converter=_make_timedelta ) #: Enable this if you want to use the X-Sendfile feature. Keep in #: mind that the server has to support this. This only affects files #: sent with the :func:`send_file` method. #: #: .. versionadded:: 0.2 #: #: This attribute can also be configured from the config with the #: ``USE_X_SENDFILE`` configuration key. Defaults to ``False``. use_x_sendfile = ConfigAttribute("USE_X_SENDFILE") #: The JSON encoder class to use. Defaults to :class:`~flask.json.JSONEncoder`. #: #: .. versionadded:: 0.10 json_encoder = json.JSONEncoder #: The JSON decoder class to use. Defaults to :class:`~flask.json.JSONDecoder`. #: #: .. versionadded:: 0.10 json_decoder = json.JSONDecoder #: Options that are passed to the Jinja environment in #: :meth:`create_jinja_environment`. Changing these options after #: the environment is created (accessing :attr:`jinja_env`) will #: have no effect. #: #: .. versionchanged:: 1.1.0 #: This is a ``dict`` instead of an ``ImmutableDict`` to allow #: easier configuration. #: jinja_options = {"extensions": ["jinja2.ext.autoescape", "jinja2.ext.with_"]} #: Default configuration parameters. default_config = ImmutableDict( { "ENV": None, "DEBUG": None, "TESTING": False, "PROPAGATE_EXCEPTIONS": None, "PRESERVE_CONTEXT_ON_EXCEPTION": None, "SECRET_KEY": None, "PERMANENT_SESSION_LIFETIME": timedelta(days=31), "USE_X_SENDFILE": False, "SERVER_NAME": None, "APPLICATION_ROOT": "/", "SESSION_COOKIE_NAME": "session", "SESSION_COOKIE_DOMAIN": None, "SESSION_COOKIE_PATH": None, "SESSION_COOKIE_HTTPONLY": True, "SESSION_COOKIE_SECURE": False, "SESSION_COOKIE_SAMESITE": None, "SESSION_REFRESH_EACH_REQUEST": True, "MAX_CONTENT_LENGTH": None, "SEND_FILE_MAX_AGE_DEFAULT": timedelta(hours=12), "TRAP_BAD_REQUEST_ERRORS": None, "TRAP_HTTP_EXCEPTIONS": False, "EXPLAIN_TEMPLATE_LOADING": False, "PREFERRED_URL_SCHEME": "http", "JSON_AS_ASCII": True, "JSON_SORT_KEYS": True, "JSONIFY_PRETTYPRINT_REGULAR": False, "JSONIFY_MIMETYPE": "application/json", "TEMPLATES_AUTO_RELOAD": None, "MAX_COOKIE_SIZE": 4093, } ) #: The rule object to use for URL rules created. This is used by #: :meth:`add_url_rule`. Defaults to :class:`werkzeug.routing.Rule`. #: #: .. versionadded:: 0.7 url_rule_class = Rule #: The map object to use for storing the URL rules and routing #: configuration parameters. Defaults to :class:`werkzeug.routing.Map`. #: #: .. versionadded:: 1.1.0 url_map_class = Map #: the test client that is used with when `test_client` is used. #: #: .. versionadded:: 0.7 test_client_class = None #: The :class:`~click.testing.CliRunner` subclass, by default #: :class:`~flask.testing.FlaskCliRunner` that is used by #: :meth:`test_cli_runner`. Its ``__init__`` method should take a #: Flask app object as the first argument. #: #: .. versionadded:: 1.0 test_cli_runner_class = None #: the session interface to use. By default an instance of #: :class:`~flask.sessions.SecureCookieSessionInterface` is used here. #: #: .. versionadded:: 0.8 session_interface = SecureCookieSessionInterface() # TODO remove the next three attrs when Sphinx :inherited-members: works # https://github.com/sphinx-doc/sphinx/issues/741 #: The name of the package or module that this app belongs to. Do not #: change this once it is set by the constructor. import_name = None #: Location of the template files to be added to the template lookup. #: ``None`` if templates should not be added. template_folder = None #: Absolute path to the package on the filesystem. Used to look up #: resources contained in the package. root_path = None def __init__( self, import_name, static_url_path=None, static_folder="static", static_host=None, host_matching=False, subdomain_matching=False, template_folder="templates", instance_path=None, instance_relative_config=False, root_path=None, ): _PackageBoundObject.__init__( self, import_name, template_folder=template_folder, root_path=root_path ) self.static_url_path = static_url_path self.static_folder = static_folder if instance_path is None: instance_path = self.auto_find_instance_path() elif not os.path.isabs(instance_path): raise ValueError( "If an instance path is provided it must be absolute." " A relative path was given instead." ) #: Holds the path to the instance folder. #: #: .. versionadded:: 0.8 self.instance_path = instance_path #: The configuration dictionary as :class:`Config`. This behaves #: exactly like a regular dictionary but supports additional methods #: to load a config from files. self.config = self.make_config(instance_relative_config) #: A dictionary of all view functions registered. The keys will #: be function names which are also used to generate URLs and #: the values are the function objects themselves. #: To register a view function, use the :meth:`route` decorator. self.view_functions = {} #: A dictionary of all registered error handlers. The key is ``None`` #: for error handlers active on the application, otherwise the key is #: the name of the blueprint. Each key points to another dictionary #: where the key is the status code of the http exception. The #: special key ``None`` points to a list of tuples where the first item #: is the class for the instance check and the second the error handler #: function. #: #: To register an error handler, use the :meth:`errorhandler` #: decorator. self.error_handler_spec = {} #: A list of functions that are called when :meth:`url_for` raises a #: :exc:`~werkzeug.routing.BuildError`. Each function registered here #: is called with `error`, `endpoint` and `values`. If a function #: returns ``None`` or raises a :exc:`BuildError` the next function is #: tried. #: #: .. versionadded:: 0.9 self.url_build_error_handlers = [] #: A dictionary with lists of functions that will be called at the #: beginning of each request. The key of the dictionary is the name of #: the blueprint this function is active for, or ``None`` for all #: requests. To register a function, use the :meth:`before_request` #: decorator. self.before_request_funcs = {} #: A list of functions that will be called at the beginning of the #: first request to this instance. To register a function, use the #: :meth:`before_first_request` decorator. #: #: .. versionadded:: 0.8 self.before_first_request_funcs = [] #: A dictionary with lists of functions that should be called after #: each request. The key of the dictionary is the name of the blueprint #: this function is active for, ``None`` for all requests. This can for #: example be used to close database connections. To register a function #: here, use the :meth:`after_request` decorator. self.after_request_funcs = {} #: A dictionary with lists of functions that are called after #: each request, even if an exception has occurred. The key of the #: dictionary is the name of the blueprint this function is active for, #: ``None`` for all requests. These functions are not allowed to modify #: the request, and their return values are ignored. If an exception #: occurred while processing the request, it gets passed to each #: teardown_request function. To register a function here, use the #: :meth:`teardown_request` decorator. #: #: .. versionadded:: 0.7 self.teardown_request_funcs = {} #: A list of functions that are called when the application context #: is destroyed. Since the application context is also torn down #: if the request ends this is the place to store code that disconnects #: from databases. #: #: .. versionadded:: 0.9 self.teardown_appcontext_funcs = [] #: A dictionary with lists of functions that are called before the #: :attr:`before_request_funcs` functions. The key of the dictionary is #: the name of the blueprint this function is active for, or ``None`` #: for all requests. To register a function, use #: :meth:`url_value_preprocessor`. #: #: .. versionadded:: 0.7 self.url_value_preprocessors = {} #: A dictionary with lists of functions that can be used as URL value #: preprocessors. The key ``None`` here is used for application wide #: callbacks, otherwise the key is the name of the blueprint. #: Each of these functions has the chance to modify the dictionary #: of URL values before they are used as the keyword arguments of the #: view function. For each function registered this one should also #: provide a :meth:`url_defaults` function that adds the parameters #: automatically again that were removed that way. #: #: .. versionadded:: 0.7 self.url_default_functions = {} #: A dictionary with list of functions that are called without argument #: to populate the template context. The key of the dictionary is the #: name of the blueprint this function is active for, ``None`` for all #: requests. Each returns a dictionary that the template context is #: updated with. To register a function here, use the #: :meth:`context_processor` decorator. self.template_context_processors = {None: [_default_template_ctx_processor]} #: A list of shell context processor functions that should be run #: when a shell context is created. #: #: .. versionadded:: 0.11 self.shell_context_processors = [] #: all the attached blueprints in a dictionary by name. Blueprints #: can be attached multiple times so this dictionary does not tell #: you how often they got attached. #: #: .. versionadded:: 0.7 self.blueprints = {} self._blueprint_order = [] #: a place where extensions can store application specific state. For #: example this is where an extension could store database engines and #: similar things. For backwards compatibility extensions should register #: themselves like this:: #: #: if not hasattr(app, 'extensions'): #: app.extensions = {} #: app.extensions['extensionname'] = SomeObject() #: #: The key must match the name of the extension module. For example in #: case of a "Flask-Foo" extension in `flask_foo`, the key would be #: ``'foo'``. #: #: .. versionadded:: 0.7 self.extensions = {} #: The :class:`~werkzeug.routing.Map` for this instance. You can use #: this to change the routing converters after the class was created #: but before any routes are connected. Example:: #: #: from werkzeug.routing import BaseConverter #: #: class ListConverter(BaseConverter): #: def to_python(self, value): #: return value.split(',') #: def to_url(self, values): #: return ','.join(super(ListConverter, self).to_url(value) #: for value in values) #: #: app = Flask(__name__) #: app.url_map.converters['list'] = ListConverter self.url_map = self.url_map_class() self.url_map.host_matching = host_matching self.subdomain_matching = subdomain_matching # tracks internally if the application already handled at least one # request. self._got_first_request = False self._before_request_lock = Lock() # Add a static route using the provided static_url_path, static_host, # and static_folder if there is a configured static_folder. # Note we do this without checking if static_folder exists. # For one, it might be created while the server is running (e.g. during # development). Also, Google App Engine stores static files somewhere if self.has_static_folder: assert ( bool(static_host) == host_matching ), "Invalid static_host/host_matching combination" self.add_url_rule( self.static_url_path + "/<path:filename>", endpoint="static", host=static_host, view_func=self.send_static_file, ) # Set the name of the Click group in case someone wants to add # the app's commands to another CLI tool. self.cli.name = self.name @locked_cached_property def name(self): """The name of the application. This is usually the import name with the difference that it's guessed from the run file if the import name is main. This name is used as a display name when Flask needs the name of the application. It can be set and overridden to change the value. .. versionadded:: 0.8 """ if self.import_name == "__main__": fn = getattr(sys.modules["__main__"], "__file__", None) if fn is None: return "__main__" return os.path.splitext(os.path.basename(fn))[0] return self.import_name @property def propagate_exceptions(self): """Returns the value of the ``PROPAGATE_EXCEPTIONS`` configuration value in case it's set, otherwise a sensible default is returned. .. versionadded:: 0.7 """ rv = self.config["PROPAGATE_EXCEPTIONS"] if rv is not None: return rv return self.testing or self.debug @property def preserve_context_on_exception(self): """Returns the value of the ``PRESERVE_CONTEXT_ON_EXCEPTION`` configuration value in case it's set, otherwise a sensible default is returned. .. versionadded:: 0.7 """ rv = self.config["PRESERVE_CONTEXT_ON_EXCEPTION"] if rv is not None: return rv return self.debug @locked_cached_property def logger(self): """A standard Python :class:`~logging.Logger` for the app, with the same name as :attr:`name`. In debug mode, the logger's :attr:`~logging.Logger.level` will be set to :data:`~logging.DEBUG`. If there are no handlers configured, a default handler will be added. See :doc:`/logging` for more information. .. versionchanged:: 1.1.0 The logger takes the same name as :attr:`name` rather than hard-coding ``"flask.app"``. .. versionchanged:: 1.0.0 Behavior was simplified. The logger is always named ``"flask.app"``. The level is only set during configuration, it doesn't check ``app.debug`` each time. Only one format is used, not different ones depending on ``app.debug``. No handlers are removed, and a handler is only added if no handlers are already configured. .. versionadded:: 0.3 """ return create_logger(self) @locked_cached_property def jinja_env(self): """The Jinja environment used to load templates. The environment is created the first time this property is accessed. Changing :attr:`jinja_options` after that will have no effect. """ return self.create_jinja_environment() @property def got_first_request(self): """This attribute is set to ``True`` if the application started handling the first request. .. versionadded:: 0.8 """ return self._got_first_request def make_config(self, instance_relative=False): """Used to create the config attribute by the Flask constructor. The `instance_relative` parameter is passed in from the constructor of Flask (there named `instance_relative_config`) and indicates if the config should be relative to the instance path or the root path of the application. .. versionadded:: 0.8 """ root_path = self.root_path if instance_relative: root_path = self.instance_path defaults = dict(self.default_config) defaults["ENV"] = get_env() defaults["DEBUG"] = get_debug_flag() return self.config_class(root_path, defaults) def auto_find_instance_path(self): """Tries to locate the instance path if it was not provided to the constructor of the application class. It will basically calculate the path to a folder named ``instance`` next to your main file or the package. .. versionadded:: 0.8 """ prefix, package_path = find_package(self.import_name) if prefix is None: return os.path.join(package_path, "instance") return os.path.join(prefix, "var", self.name + "-instance") def open_instance_resource(self, resource, mode="rb"): """Opens a resource from the application's instance folder (:attr:`instance_path`). Otherwise works like :meth:`open_resource`. Instance resources can also be opened for writing. :param resource: the name of the resource. To access resources within subfolders use forward slashes as separator. :param mode: resource file opening mode, default is 'rb'. """ return open(os.path.join(self.instance_path, resource), mode) @property def templates_auto_reload(self): """Reload templates when they are changed. Used by :meth:`create_jinja_environment`. This attribute can be configured with :data:`TEMPLATES_AUTO_RELOAD`. If not set, it will be enabled in debug mode. .. versionadded:: 1.0 This property was added but the underlying config and behavior already existed. """ rv = self.config["TEMPLATES_AUTO_RELOAD"] return rv if rv is not None else self.debug @templates_auto_reload.setter def templates_auto_reload(self, value): self.config["TEMPLATES_AUTO_RELOAD"] = value def create_jinja_environment(self): """Create the Jinja environment based on :attr:`jinja_options` and the various Jinja-related methods of the app. Changing :attr:`jinja_options` after this will have no effect. Also adds Flask-related globals and filters to the environment. .. versionchanged:: 0.11 ``Environment.auto_reload`` set in accordance with ``TEMPLATES_AUTO_RELOAD`` configuration option. .. versionadded:: 0.5 """ options = dict(self.jinja_options) if "autoescape" not in options: options["autoescape"] = self.select_jinja_autoescape if "auto_reload" not in options: options["auto_reload"] = self.templates_auto_reload rv = self.jinja_environment(self, **options) rv.globals.update( url_for=url_for, get_flashed_messages=get_flashed_messages, config=self.config, # request, session and g are normally added with the # context processor for efficiency reasons but for imported # templates we also want the proxies in there. request=request, session=session, g=g, ) rv.filters["tojson"] = json.tojson_filter return rv def create_global_jinja_loader(self): """Creates the loader for the Jinja2 environment. Can be used to override just the loader and keeping the rest unchanged. It's discouraged to override this function. Instead one should override the :meth:`jinja_loader` function instead. The global loader dispatches between the loaders of the application and the individual blueprints. .. versionadded:: 0.7 """ return DispatchingJinjaLoader(self) def select_jinja_autoescape(self, filename): """Returns ``True`` if autoescaping should be active for the given template name. If no template name is given, returns `True`. .. versionadded:: 0.5 """ if filename is None: return True return filename.endswith((".html", ".htm", ".xml", ".xhtml")) def update_template_context(self, context): """Update the template context with some commonly used variables. This injects request, session, config and g into the template context as well as everything template context processors want to inject. Note that the as of Flask 0.6, the original values in the context will not be overridden if a context processor decides to return a value with the same key. :param context: the context as a dictionary that is updated in place to add extra variables. """ funcs = self.template_context_processors[None] reqctx = _request_ctx_stack.top if reqctx is not None: bp = reqctx.request.blueprint if bp is not None and bp in self.template_context_processors: funcs = chain(funcs, self.template_context_processors[bp]) orig_ctx = context.copy() for func in funcs: context.update(func()) # make sure the original values win. This makes it possible to # easier add new variables in context processors without breaking # existing views. context.update(orig_ctx) def make_shell_context(self): """Returns the shell context for an interactive shell for this application. This runs all the registered shell context processors. .. versionadded:: 0.11 """ rv = {"app": self, "g": g} for processor in self.shell_context_processors: rv.update(processor()) return rv #: What environment the app is running in. Flask and extensions may #: enable behaviors based on the environment, such as enabling debug #: mode. This maps to the :data:`ENV` config key. This is set by the #: :envvar:`FLASK_ENV` environment variable and may not behave as #: expected if set in code. #: #: **Do not enable development when deploying in production.** #: #: Default: ``'production'`` env = ConfigAttribute("ENV") @property def debug(self): """Whether debug mode is enabled. When using ``flask run`` to start the development server, an interactive debugger will be shown for unhandled exceptions, and the server will be reloaded when code changes. This maps to the :data:`DEBUG` config key. This is enabled when :attr:`env` is ``'development'`` and is overridden by the ``FLASK_DEBUG`` environment variable. It may not behave as expected if set in code. **Do not enable debug mode when deploying in production.** Default: ``True`` if :attr:`env` is ``'development'``, or ``False`` otherwise. """ return self.config["DEBUG"] @debug.setter def debug(self, value): self.config["DEBUG"] = value self.jinja_env.auto_reload = self.templates_auto_reload def run(self, host=None, port=None, debug=None, load_dotenv=True, **options): """Runs the application on a local development server. Do not use ``run()`` in a production setting. It is not intended to meet security and performance requirements for a production server. Instead, see :ref:`deployment` for WSGI server recommendations. If the :attr:`debug` flag is set the server will automatically reload for code changes and show a debugger in case an exception happened. If you want to run the application in debug mode, but disable the code execution on the interactive debugger, you can pass ``use_evalex=False`` as parameter. This will keep the debugger's traceback screen active, but disable code execution. It is not recommended to use this function for development with automatic reloading as this is badly supported. Instead you should be using the :command:`flask` command line script's ``run`` support. .. admonition:: Keep in Mind Flask will suppress any server error with a generic error page unless it is in debug mode. As such to enable just the interactive debugger without the code reloading, you have to invoke :meth:`run` with ``debug=True`` and ``use_reloader=False``. Setting ``use_debugger`` to ``True`` without being in debug mode won't catch any exceptions because there won't be any to catch. :param host: the hostname to listen on. Set this to ``'0.0.0.0'`` to have the server available externally as well. Defaults to ``'127.0.0.1'`` or the host in the ``SERVER_NAME`` config variable if present. :param port: the port of the webserver. Defaults to ``5000`` or the port defined in the ``SERVER_NAME`` config variable if present. :param debug: if given, enable or disable debug mode. See :attr:`debug`. :param load_dotenv: Load the nearest :file:`.env` and :file:`.flaskenv` files to set environment variables. Will also change the working directory to the directory containing the first file found. :param options: the options to be forwarded to the underlying Werkzeug server. See :func:`werkzeug.serving.run_simple` for more information. .. versionchanged:: 1.0 If installed, python-dotenv will be used to load environment variables from :file:`.env` and :file:`.flaskenv` files. If set, the :envvar:`FLASK_ENV` and :envvar:`FLASK_DEBUG` environment variables will override :attr:`env` and :attr:`debug`. Threaded mode is enabled by default. .. versionchanged:: 0.10 The default port is now picked from the ``SERVER_NAME`` variable. """ # Change this into a no-op if the server is invoked from the # command line. Have a look at cli.py for more information. if os.environ.get("FLASK_RUN_FROM_CLI") == "true": from .debughelpers import explain_ignored_app_run explain_ignored_app_run() return if get_load_dotenv(load_dotenv): cli.load_dotenv() # if set, let env vars override previous values if "FLASK_ENV" in os.environ: self.env = get_env() self.debug = get_debug_flag() elif "FLASK_DEBUG" in os.environ: self.debug = get_debug_flag() # debug passed to method overrides all other sources if debug is not None: self.debug = bool(debug) _host = "127.0.0.1" _port = 5000 server_name = self.config.get("SERVER_NAME") sn_host, sn_port = None, None if server_name: sn_host, _, sn_port = server_name.partition(":") host = host or sn_host or _host # pick the first value that's not None (0 is allowed) port = int(next((p for p in (port, sn_port) if p is not None), _port)) options.setdefault("use_reloader", self.debug) options.setdefault("use_debugger", self.debug) options.setdefault("threaded", True) cli.show_server_banner(self.env, self.debug, self.name, False) from werkzeug.serving import run_simple try: run_simple(host, port, self, **options) finally: # reset the first request information if the development server # reset normally. This makes it possible to restart the server # without reloader and that stuff from an interactive shell. self._got_first_request = False def test_client(self, use_cookies=True, **kwargs): """Creates a test client for this application. For information about unit testing head over to :ref:`testing`. Note that if you are testing for assertions or exceptions in your application code, you must set ``app.testing = True`` in order for the exceptions to propagate to the test client. Otherwise, the exception will be handled by the application (not visible to the test client) and the only indication of an AssertionError or other exception will be a 500 status code response to the test client. See the :attr:`testing` attribute. For example:: app.testing = True client = app.test_client() The test client can be used in a ``with`` block to defer the closing down of the context until the end of the ``with`` block. This is useful if you want to access the context locals for testing:: with app.test_client() as c: rv = c.get('/?vodka=42') assert request.args['vodka'] == '42' Additionally, you may pass optional keyword arguments that will then be passed to the application's :attr:`test_client_class` constructor. For example:: from flask.testing import FlaskClient class CustomClient(FlaskClient): def __init__(self, *args, **kwargs): self._authentication = kwargs.pop("authentication") super(CustomClient,self).__init__( *args, **kwargs) app.test_client_class = CustomClient client = app.test_client(authentication='Basic ....') See :class:`~flask.testing.FlaskClient` for more information. .. versionchanged:: 0.4 added support for ``with`` block usage for the client. .. versionadded:: 0.7 The `use_cookies` parameter was added as well as the ability to override the client to be used by setting the :attr:`test_client_class` attribute. .. versionchanged:: 0.11 Added `**kwargs` to support passing additional keyword arguments to the constructor of :attr:`test_client_class`. """ cls = self.test_client_class if cls is None: from .testing import FlaskClient as cls return cls(self, self.response_class, use_cookies=use_cookies, **kwargs) def test_cli_runner(self, **kwargs): """Create a CLI runner for testing CLI commands. See :ref:`testing-cli`. Returns an instance of :attr:`test_cli_runner_class`, by default :class:`~flask.testing.FlaskCliRunner`. The Flask app object is passed as the first argument. .. versionadded:: 1.0 """ cls = self.test_cli_runner_class if cls is None: from .testing import FlaskCliRunner as cls return cls(self, **kwargs) def open_session(self, request): """Creates or opens a new session. Default implementation stores all session data in a signed cookie. This requires that the :attr:`secret_key` is set. Instead of overriding this method we recommend replacing the :class:`session_interface`. .. deprecated: 1.0 Will be removed in 2.0. Use ``session_interface.open_session`` instead. :param request: an instance of :attr:`request_class`. """ warnings.warn( DeprecationWarning( '"open_session" is deprecated and will be removed in' ' 2.0. Use "session_interface.open_session" instead.' ) ) return self.session_interface.open_session(self, request) def save_session(self, session, response): """Saves the session if it needs updates. For the default implementation, check :meth:`open_session`. Instead of overriding this method we recommend replacing the :class:`session_interface`. .. deprecated: 1.0 Will be removed in 2.0. Use ``session_interface.save_session`` instead. :param session: the session to be saved (a :class:`~werkzeug.contrib.securecookie.SecureCookie` object) :param response: an instance of :attr:`response_class` """ warnings.warn( DeprecationWarning( '"save_session" is deprecated and will be removed in' ' 2.0. Use "session_interface.save_session" instead.' ) ) return self.session_interface.save_session(self, session, response) def make_null_session(self): """Creates a new instance of a missing session. Instead of overriding this method we recommend replacing the :class:`session_interface`. .. deprecated: 1.0 Will be removed in 2.0. Use ``session_interface.make_null_session`` instead. .. versionadded:: 0.7 """ warnings.warn( DeprecationWarning( '"make_null_session" is deprecated and will be removed' ' in 2.0. Use "session_interface.make_null_session"' " instead." ) ) return self.session_interface.make_null_session(self) @setupmethod def register_blueprint(self, blueprint, **options): """Register a :class:`~flask.Blueprint` on the application. Keyword arguments passed to this method will override the defaults set on the blueprint. Calls the blueprint's :meth:`~flask.Blueprint.register` method after recording the blueprint in the application's :attr:`blueprints`. :param blueprint: The blueprint to register. :param url_prefix: Blueprint routes will be prefixed with this. :param subdomain: Blueprint routes will match on this subdomain. :param url_defaults: Blueprint routes will use these default values for view arguments. :param options: Additional keyword arguments are passed to :class:`~flask.blueprints.BlueprintSetupState`. They can be accessed in :meth:`~flask.Blueprint.record` callbacks. .. versionadded:: 0.7 """ first_registration = False if blueprint.name in self.blueprints: assert self.blueprints[blueprint.name] is blueprint, ( "A name collision occurred between blueprints %r and %r. Both" ' share the same name "%s". Blueprints that are created on the' " fly need unique names." % (blueprint, self.blueprints[blueprint.name], blueprint.name) ) else: self.blueprints[blueprint.name] = blueprint self._blueprint_order.append(blueprint) first_registration = True blueprint.register(self, options, first_registration) def iter_blueprints(self): """Iterates over all blueprints by the order they were registered. .. versionadded:: 0.11 """ return iter(self._blueprint_order) @setupmethod def add_url_rule( self, rule, endpoint=None, view_func=None, provide_automatic_options=None, **options ): """Connects a URL rule. Works exactly like the :meth:`route` decorator. If a view_func is provided it will be registered with the endpoint. Basically this example:: @app.route('/') def index(): pass Is equivalent to the following:: def index(): pass app.add_url_rule('/', 'index', index) If the view_func is not provided you will need to connect the endpoint to a view function like so:: app.view_functions['index'] = index Internally :meth:`route` invokes :meth:`add_url_rule` so if you want to customize the behavior via subclassing you only need to change this method. For more information refer to :ref:`url-route-registrations`. .. versionchanged:: 0.2 `view_func` parameter added. .. versionchanged:: 0.6 ``OPTIONS`` is added automatically as method. :param rule: the URL rule as string :param endpoint: the endpoint for the registered URL rule. Flask itself assumes the name of the view function as endpoint :param view_func: the function to call when serving a request to the provided endpoint :param provide_automatic_options: controls whether the ``OPTIONS`` method should be added automatically. This can also be controlled by setting the ``view_func.provide_automatic_options = False`` before adding the rule. :param options: the options to be forwarded to the underlying :class:`~werkzeug.routing.Rule` object. A change to Werkzeug is handling of method options. methods is a list of methods this rule should be limited to (``GET``, ``POST`` etc.). By default a rule just listens for ``GET`` (and implicitly ``HEAD``). Starting with Flask 0.6, ``OPTIONS`` is implicitly added and handled by the standard request handling. """ if endpoint is None: endpoint = _endpoint_from_view_func(view_func) options["endpoint"] = endpoint methods = options.pop("methods", None) # if the methods are not given and the view_func object knows its # methods we can use that instead. If neither exists, we go with # a tuple of only ``GET`` as default. if methods is None: methods = getattr(view_func, "methods", None) or ("GET",) if isinstance(methods, string_types): raise TypeError( "Allowed methods have to be iterables of strings, " 'for example: @app.route(..., methods=["POST"])' ) methods = set(item.upper() for item in methods) # Methods that should always be added required_methods = set(getattr(view_func, "required_methods", ())) # starting with Flask 0.8 the view_func object can disable and # force-enable the automatic options handling. if provide_automatic_options is None: provide_automatic_options = getattr( view_func, "provide_automatic_options", None ) if provide_automatic_options is None: if "OPTIONS" not in methods: provide_automatic_options = True required_methods.add("OPTIONS") else: provide_automatic_options = False # Add the required methods now. methods |= required_methods rule = self.url_rule_class(rule, methods=methods, **options) rule.provide_automatic_options = provide_automatic_options self.url_map.add(rule) if view_func is not None: old_func = self.view_functions.get(endpoint) if old_func is not None and old_func != view_func: raise AssertionError( "View function mapping is overwriting an " "existing endpoint function: %s" % endpoint ) self.view_functions[endpoint] = view_func def route(self, rule, **options): """A decorator that is used to register a view function for a given URL rule. This does the same thing as :meth:`add_url_rule` but is intended for decorator usage:: @app.route('/') def index(): return 'Hello World' For more information refer to :ref:`url-route-registrations`. :param rule: the URL rule as string :param endpoint: the endpoint for the registered URL rule. Flask itself assumes the name of the view function as endpoint :param options: the options to be forwarded to the underlying :class:`~werkzeug.routing.Rule` object. A change to Werkzeug is handling of method options. methods is a list of methods this rule should be limited to (``GET``, ``POST`` etc.). By default a rule just listens for ``GET`` (and implicitly ``HEAD``). Starting with Flask 0.6, ``OPTIONS`` is implicitly added and handled by the standard request handling. """ def decorator(f): endpoint = options.pop("endpoint", None) self.add_url_rule(rule, endpoint, f, **options) return f return decorator @setupmethod def endpoint(self, endpoint): """A decorator to register a function as an endpoint. Example:: @app.endpoint('example.endpoint') def example(): return "example" :param endpoint: the name of the endpoint """ def decorator(f): self.view_functions[endpoint] = f return f return decorator @staticmethod def _get_exc_class_and_code(exc_class_or_code): """Get the exception class being handled. For HTTP status codes or ``HTTPException`` subclasses, return both the exception and status code. :param exc_class_or_code: Any exception class, or an HTTP status code as an integer. """ if isinstance(exc_class_or_code, integer_types): exc_class = default_exceptions[exc_class_or_code] else: exc_class = exc_class_or_code assert issubclass(exc_class, Exception) if issubclass(exc_class, HTTPException): return exc_class, exc_class.code else: return exc_class, None @setupmethod def errorhandler(self, code_or_exception): """Register a function to handle errors by code or exception class. A decorator that is used to register a function given an error code. Example:: @app.errorhandler(404) def page_not_found(error): return 'This page does not exist', 404 You can also register handlers for arbitrary exceptions:: @app.errorhandler(DatabaseError) def special_exception_handler(error): return 'Database connection failed', 500 .. versionadded:: 0.7 Use :meth:`register_error_handler` instead of modifying :attr:`error_handler_spec` directly, for application wide error handlers. .. versionadded:: 0.7 One can now additionally also register custom exception types that do not necessarily have to be a subclass of the :class:`~werkzeug.exceptions.HTTPException` class. :param code_or_exception: the code as integer for the handler, or an arbitrary exception """ def decorator(f): self._register_error_handler(None, code_or_exception, f) return f return decorator @setupmethod def register_error_handler(self, code_or_exception, f): """Alternative error attach function to the :meth:`errorhandler` decorator that is more straightforward to use for non decorator usage. .. versionadded:: 0.7 """ self._register_error_handler(None, code_or_exception, f) @setupmethod def _register_error_handler(self, key, code_or_exception, f): """ :type key: None|str :type code_or_exception: int|T<=Exception :type f: callable """ if isinstance(code_or_exception, HTTPException): # old broken behavior raise ValueError( "Tried to register a handler for an exception instance {0!r}." " Handlers can only be registered for exception classes or" " HTTP error codes.".format(code_or_exception) ) try: exc_class, code = self._get_exc_class_and_code(code_or_exception) except KeyError: raise KeyError( "'{0}' is not a recognized HTTP error code. Use a subclass of" " HTTPException with that code instead.".format(code_or_exception) ) handlers = self.error_handler_spec.setdefault(key, {}).setdefault(code, {}) handlers[exc_class] = f @setupmethod def template_filter(self, name=None): """A decorator that is used to register custom template filter. You can specify a name for the filter, otherwise the function name will be used. Example:: @app.template_filter() def reverse(s): return s[::-1] :param name: the optional name of the filter, otherwise the function name will be used. """ def decorator(f): self.add_template_filter(f, name=name) return f return decorator @setupmethod def add_template_filter(self, f, name=None): """Register a custom template filter. Works exactly like the :meth:`template_filter` decorator. :param name: the optional name of the filter, otherwise the function name will be used. """ self.jinja_env.filters[name or f.__name__] = f @setupmethod def template_test(self, name=None): """A decorator that is used to register custom template test. You can specify a name for the test, otherwise the function name will be used. Example:: @app.template_test() def is_prime(n): if n == 2: return True for i in range(2, int(math.ceil(math.sqrt(n))) + 1): if n % i == 0: return False return True .. versionadded:: 0.10 :param name: the optional name of the test, otherwise the function name will be used. """ def decorator(f): self.add_template_test(f, name=name) return f return decorator @setupmethod def add_template_test(self, f, name=None): """Register a custom template test. Works exactly like the :meth:`template_test` decorator. .. versionadded:: 0.10 :param name: the optional name of the test, otherwise the function name will be used. """ self.jinja_env.tests[name or f.__name__] = f @setupmethod def template_global(self, name=None): """A decorator that is used to register a custom template global function. You can specify a name for the global function, otherwise the function name will be used. Example:: @app.template_global() def double(n): return 2 * n .. versionadded:: 0.10 :param name: the optional name of the global function, otherwise the function name will be used. """ def decorator(f): self.add_template_global(f, name=name) return f return decorator @setupmethod def add_template_global(self, f, name=None): """Register a custom template global function. Works exactly like the :meth:`template_global` decorator. .. versionadded:: 0.10 :param name: the optional name of the global function, otherwise the function name will be used. """ self.jinja_env.globals[name or f.__name__] = f @setupmethod def before_request(self, f): """Registers a function to run before each request. For example, this can be used to open a database connection, or to load the logged in user from the session. The function will be called without any arguments. If it returns a non-None value, the value is handled as if it was the return value from the view, and further request handling is stopped. """ self.before_request_funcs.setdefault(None, []).append(f) return f @setupmethod def before_first_request(self, f): """Registers a function to be run before the first request to this instance of the application. The function will be called without any arguments and its return value is ignored. .. versionadded:: 0.8 """ self.before_first_request_funcs.append(f) return f @setupmethod def after_request(self, f): """Register a function to be run after each request. Your function must take one parameter, an instance of :attr:`response_class` 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 @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 an exception it will be passed an error object. The return values of teardown functions are ignored. .. admonition:: Debug Note In debug mode Flask will not tear down a request on an exception immediately. Instead it 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 @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 unhandled exception it will be passed an error object. If an :meth:`errorhandler` is registered, it will handle the exception and the teardown will not receive it. The return values of teardown functions are ignored. .. versionadded:: 0.9 """ self.teardown_appcontext_funcs.append(f) return f @setupmethod def context_processor(self, f): """Registers a template context processor function.""" self.template_context_processors[None].append(f) return f @setupmethod def shell_context_processor(self, f): """Registers a shell context processor function. .. versionadded:: 0.11 """ self.shell_context_processors.append(f) return f @setupmethod def url_value_preprocessor(self, f): """Register a URL value preprocessor function for all view functions in the application. These functions will be called before the :meth:`before_request` functions. The function can modify the values captured from the matched url before they are passed to the view. For example, this can be used to pop a common language code value and place it in ``g`` rather than pass it to every view. The function is passed the endpoint name and values dict. The return value is ignored. """ self.url_value_preprocessors.setdefault(None, []).append(f) return f @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 def _find_error_handler(self, e): """Return a registered error handler for an exception in this order: blueprint handler for a specific code, app handler for a specific code, blueprint handler for an exception class, app handler for an exception class, or ``None`` if a suitable handler is not found. """ exc_class, code = self._get_exc_class_and_code(type(e)) for name, c in ( (request.blueprint, code), (None, code), (request.blueprint, None), (None, None), ): handler_map = self.error_handler_spec.setdefault(name, {}).get(c) if not handler_map: continue for cls in exc_class.__mro__: handler = handler_map.get(cls) if handler is not None: return handler 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. .. versionchanged:: 1.0.3 ``RoutingException``, used internally for actions such as slash redirects during routing, is not passed to error handlers. .. versionchanged:: 1.0 Exceptions are looked up by code *and* by MRO, so ``HTTPExcpetion`` subclasses can be handled with a catch-all handler for the base ``HTTPException``. .. versionadded:: 0.3 """ # Proxy exceptions don't have error codes. We want to always return # those unchanged as errors if e.code is None: return e # RoutingExceptions are used internally to trigger routing # actions, such as slash redirects raising RequestRedirect. They # are not raised or handled in user code. if isinstance(e, RoutingException): return e handler = self._find_error_handler(e) if handler is None: return e return handler(e) 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. .. versionchanged:: 1.0 Bad request errors are not trapped by default in debug mode. .. versionadded:: 0.8 """ if self.config["TRAP_HTTP_EXCEPTIONS"]: return True trap_bad_request = self.config["TRAP_BAD_REQUEST_ERRORS"] # if unset, trap key errors in debug mode if ( trap_bad_request is None and self.debug and isinstance(e, BadRequestKeyError) ): return True if trap_bad_request: return isinstance(e, BadRequest) return False def handle_user_exception(self, e): """This method is called whenever an exception occurs that should be handled. A special case is :class:`~werkzeug .exceptions.HTTPException` which is forwarded to the :meth:`handle_http_exception` method. This function will either return a response value or reraise the exception with the same traceback. .. versionchanged:: 1.0 Key errors raised from request data like ``form`` show the bad key in debug mode rather than a generic bad request message. .. 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, BadRequestKeyError): if self.debug or self.config["TRAP_BAD_REQUEST_ERRORS"]: e.show_exception = True # Werkzeug < 0.15 doesn't add the KeyError to the 400 # message, add it in manually. # TODO: clean up once Werkzeug >= 0.15.5 is required if e.args[0] not in e.get_description(): e.description = "KeyError: '{}'".format(*e.args) elif not hasattr(BadRequestKeyError, "show_exception"): e.args = () if isinstance(e, HTTPException) and not self.trap_http_exception(e): return self.handle_http_exception(e) handler = self._find_error_handler(e) if handler is None: reraise(exc_type, exc_value, tb) return handler(e) def handle_exception(self, e): """Handle an exception that did not have an error handler associated with it, or that was raised from an error handler. This always causes a 500 ``InternalServerError``. Always sends the :data:`got_request_exception` signal. If :attr:`propagate_exceptions` is ``True``, such as in debug mode, the error will be re-raised so that the debugger can display it. Otherwise, the original exception is logged, and an :exc:`~werkzeug.exceptions.InternalServerError` is returned. If an error handler is registered for ``InternalServerError`` or ``500``, it will be used. For consistency, the handler will always receive the ``InternalServerError``. The original unhandled exception is available as ``e.original_exception``. .. note:: Prior to Werkzeug 1.0.0, ``InternalServerError`` will not always have an ``original_exception`` attribute. Use ``getattr(e, "original_exception", None)`` to simulate the behavior for compatibility. .. versionchanged:: 1.1.0 Always passes the ``InternalServerError`` instance to the handler, setting ``original_exception`` to the unhandled error. .. versionchanged:: 1.1.0 ``after_request`` functions and other finalization is done even for the default 500 response when there is no handler. .. versionadded:: 0.3 """ exc_type, exc_value, tb = sys.exc_info() got_request_exception.send(self, exception=e) 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)) server_error = InternalServerError() # TODO: pass as param when Werkzeug>=1.0.0 is required # TODO: also remove note about this from docstring and docs server_error.original_exception = e handler = self._find_error_handler(server_error) if handler is not None: server_error = handler(server_error) return self.finalize_request(server_error, from_error_handler=True) 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 ) 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) 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) 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) return self.finalize_request(rv) def finalize_request(self, rv, from_error_handler=False): """Given the return value from a view function this finalizes the request by converting it into a response and invoking the postprocessing functions. This is invoked for both normal request dispatching as well as error handlers. Because this means that it might be called as a result of a failure a special safe mode is available which can be enabled with the `from_error_handler` flag. If enabled, failures in response processing will be logged and otherwise ignored. :internal: """ response = self.make_response(rv) try: response = self.process_response(response) request_finished.send(self, response=response) except Exception: if not from_error_handler: raise self.logger.exception( "Request finalizing failed with an error while handling an error" ) return response 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 for func in self.before_first_request_funcs: func() self._got_first_request = True 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: pass rv = self.response_class() rv.allow.update(methods) return rv 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 def make_response(self, rv): """Convert the return value from a view function to an instance of :attr:`response_class`. :param rv: the return value from the view function. The view function must return a response. Returning ``None``, or the view ending without returning, is not allowed. The following types are allowed for ``view_rv``: ``str`` (``unicode`` in Python 2) A response object is created with the string encoded to UTF-8 as the body. ``bytes`` (``str`` in Python 2) A response object is created with the bytes as the body. ``dict`` A dictionary that will be jsonify'd before being returned. ``tuple`` Either ``(body, status, headers)``, ``(body, status)``, or ``(body, headers)``, where ``body`` is any of the other types allowed here, ``status`` is a string or an integer, and ``headers`` is a dictionary or a list of ``(key, value)`` tuples. If ``body`` is a :attr:`response_class` instance, ``status`` overwrites the exiting value and ``headers`` are extended. :attr:`response_class` The object is returned unchanged. other :class:`~werkzeug.wrappers.Response` class The object is coerced to :attr:`response_class`. :func:`callable` The function is called as a WSGI application. The result is used to create a response object. .. versionchanged:: 0.9 Previously a tuple was interpreted as the arguments for the response object. """ status = headers = None # unpack tuple returns if isinstance(rv, tuple): len_rv = len(rv) # a 3-tuple is unpacked directly if len_rv == 3: rv, status, headers = rv # decide if a 2-tuple has status or headers elif len_rv == 2: if isinstance(rv[1], (Headers, dict, tuple, list)): rv, headers = rv else: rv, status = rv # other sized tuples are not allowed else: raise TypeError( "The view function did not return a valid response tuple." " The tuple must have the form (body, status, headers)," " (body, status), or (body, headers)." ) # the body must not be None if rv is None: raise TypeError( "The view function did not return a valid response. The" " function either returned None or ended without a return" " statement." ) # make sure the body is an instance of the response class if not isinstance(rv, self.response_class): if isinstance(rv, (text_type, bytes, bytearray)): # let the response class set the status and headers instead of # waiting to do it manually, so that the class can handle any # special logic rv = self.response_class(rv, status=status, headers=headers) status = headers = None elif isinstance(rv, dict): rv = jsonify(rv) elif isinstance(rv, BaseResponse) or callable(rv): # evaluate a WSGI callable, or coerce a different response # class to the correct type try: rv = self.response_class.force_type(rv, request.environ) except TypeError as e: new_error = TypeError( "{e}\nThe view function did not return a valid" " response. The return type must be a string, dict, tuple," " Response instance, or WSGI callable, but it was a" " {rv.__class__.__name__}.".format(e=e, rv=rv) ) reraise(TypeError, new_error, sys.exc_info()[2]) else: raise TypeError( "The view function did not return a valid" " response. The return type must be a string, dict, tuple," " Response instance, or WSGI callable, but it was a" " {rv.__class__.__name__}.".format(rv=rv) ) # prefer the status if it was provided if status is not None: if isinstance(status, (text_type, bytes, bytearray)): rv.status = status else: rv.status_code = status # extend existing headers with provided headers if headers: rv.headers.extend(headers) return rv 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. .. versionchanged:: 1.0 :data:`SERVER_NAME` no longer implicitly enables subdomain matching. Use :attr:`subdomain_matching` instead. """ if request is not None: # If subdomain matching is disabled (the default), use the # default subdomain in all cases. This should be the default # in Werkzeug but it currently does not have that feature. subdomain = ( (self.url_map.default_subdomain or None) if not self.subdomain_matching else None ) return self.url_map.bind_to_environ( request.environ, server_name=self.config["SERVER_NAME"], subdomain=subdomain, ) # 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"], url_scheme=self.config["PREFERRED_URL_SCHEME"], ) 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) 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 e: # make error available outside except block (py3) error = e # 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 def preprocess_request(self): """Called before the request is dispatched. Calls :attr:`url_value_preprocessors` registered with the app and the current blueprint (if any). Then calls :attr:`before_request_funcs` registered with the app and the blueprint. If any :meth:`before_request` handler returns a non-None value, the value is handled as if it was the return value from the view, and further request handling is stopped. """ 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 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.session_interface.save_session(self, ctx.session, response) return response def do_teardown_request(self, exc=_sentinel): """Called after the request is dispatched and the response is returned, right before the request context is popped. This calls all functions decorated with :meth:`teardown_request`, and :meth:`Blueprint.teardown_request` if a blueprint handled the request. Finally, the :data:`request_tearing_down` signal is sent. This is called by :meth:`RequestContext.pop() <flask.ctx.RequestContext.pop>`, which may be delayed during testing to maintain access to resources. :param exc: An unhandled exception raised while dispatching the request. Detected from the current exception information if not passed. Passed to each teardown function. .. versionchanged:: 0.9 Added the ``exc`` argument. """ if exc is _sentinel: 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: func(exc) request_tearing_down.send(self, exc=exc) def do_teardown_appcontext(self, exc=_sentinel): """Called right before the application context is popped. When handling a request, the application context is popped after the request context. See :meth:`do_teardown_request`. This calls all functions decorated with :meth:`teardown_appcontext`. Then the :data:`appcontext_tearing_down` signal is sent. This is called by :meth:`AppContext.pop() <flask.ctx.AppContext.pop>`. .. versionadded:: 0.9 """ if exc is _sentinel: exc = sys.exc_info()[1] for func in reversed(self.teardown_appcontext_funcs): func(exc) appcontext_tearing_down.send(self, exc=exc) def app_context(self): """Create an :class:`~flask.ctx.AppContext`. Use as a ``with`` block to push the context, which will make :data:`current_app` point at this application. An application context is automatically pushed by :meth:`RequestContext.push() <flask.ctx.RequestContext.push>` when handling a request, and when running a CLI command. Use this to manually create a context outside of these situations. :: with app.app_context(): init_db() See :doc:`/appcontext`. .. versionadded:: 0.9 """ return AppContext(self) def request_context(self, environ): """Create a :class:`~flask.ctx.RequestContext` representing a WSGI environment. Use a ``with`` block to push the context, which will make :data:`request` point at this request. See :doc:`/reqcontext`. Typically you should not call this from your own code. A request context is automatically pushed by the :meth:`wsgi_app` when handling a request. Use :meth:`test_request_context` to create an environment and context instead of this method. :param environ: a WSGI environment """ return RequestContext(self, environ) def test_request_context(self, *args, **kwargs): """Create a :class:`~flask.ctx.RequestContext` for a WSGI environment created from the given values. This is mostly useful during testing, where you may want to run a function that uses request data without dispatching a full request. See :doc:`/reqcontext`. Use a ``with`` block to push the context, which will make :data:`request` point at the request for the created environment. :: with test_request_context(...): generate_report() When using the shell, it may be easier to push and pop the context manually to avoid indentation. :: ctx = app.test_request_context(...) ctx.push() ... ctx.pop() Takes the same arguments as Werkzeug's :class:`~werkzeug.test.EnvironBuilder`, with some defaults from the application. See the linked Werkzeug docs for most of the available arguments. Flask-specific behavior is listed here. :param path: URL path being requested. :param base_url: Base URL where the app is being served, which ``path`` is relative to. If not given, built from :data:`PREFERRED_URL_SCHEME`, ``subdomain``, :data:`SERVER_NAME`, and :data:`APPLICATION_ROOT`. :param subdomain: Subdomain name to append to :data:`SERVER_NAME`. :param url_scheme: Scheme to use instead of :data:`PREFERRED_URL_SCHEME`. :param data: The request body, either as a string or a dict of form keys and values. :param json: If given, this is serialized as JSON and passed as ``data``. Also defaults ``content_type`` to ``application/json``. :param args: other positional arguments passed to :class:`~werkzeug.test.EnvironBuilder`. :param kwargs: other keyword arguments passed to :class:`~werkzeug.test.EnvironBuilder`. """ from .testing import EnvironBuilder builder = EnvironBuilder(self, *args, **kwargs) try: return self.request_context(builder.get_environ()) finally: builder.close() def wsgi_app(self, environ, start_response): """The actual WSGI application. This is not implemented in :meth:`__call__` so that middlewares can be applied without losing a reference to the app object. 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 Teardown events for the request and app contexts are called even if an unhandled error occurs. Other events may not be called depending on when an error occurs during dispatch. 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) error = None try: try: ctx.push() response = self.full_dispatch_request() except Exception as e: error = e response = self.handle_exception(e) except: # noqa: B001 error = sys.exc_info()[1] raise return response(environ, start_response) finally: if self.should_ignore_error(error): error = None ctx.auto_pop(error) def __call__(self, environ, start_response): """The WSGI server calls the Flask application object as the WSGI application. This calls :meth:`wsgi_app` which can be wrapped to applying middleware.""" return self.wsgi_app(environ, start_response) def __repr__(self): return "<%s %r>" % (self.__class__.__name__, self.name)
def wsgi_app(self, environ, start_response): """The actual WSGI application. This is not implemented in :meth:`__call__` so that middlewares can be applied without losing a reference to the app object. 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 Teardown events for the request and app contexts are called even if an unhandled error occurs. Other events may not be called depending on when an error occurs during dispatch. 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) error = None try: try: ctx.push() response = self.full_dispatch_request() except Exception as e: error = e response = self.handle_exception(e) except: # noqa: B001 error = sys.exc_info()[1] raise return response(environ, start_response) finally: if self.should_ignore_error(error): error = None ctx.auto_pop(error)
（三）RequestContext类
class RequestContext(object): """The request context contains all request relevant information. It is created at the beginning of the request and pushed to the `_request_ctx_stack` and removed at the end of it. It will create the URL adapter and request object for the WSGI environment provided. Do not attempt to use this class directly, instead use :meth:`~flask.Flask.test_request_context` and :meth:`~flask.Flask.request_context` to create this object. When the request context is popped, it will evaluate all the functions registered on the application for teardown execution (:meth:`~flask.Flask.teardown_request`). The request context is automatically popped at the end of the request for you. In debug mode the request context is kept around if exceptions happen so that interactive debuggers have a chance to introspect the data. With 0.4 this can also be forced for requests that did not fail and outside of ``DEBUG`` mode. By setting ``'flask._preserve_context'`` to ``True`` on the WSGI environment the context will not pop itself at the end of the request. This is used by the :meth:`~flask.Flask.test_client` for example to implement the deferred cleanup functionality. You might find this helpful for unittests where you need the information from the context local around for a little longer. Make sure to properly :meth:`~werkzeug.LocalStack.pop` the stack yourself in that situation, otherwise your unittests will leak memory. """ def __init__(self, app, environ, request=None, session=None): self.app = app if request is None: request = app.request_class(environ) self.request = request self.url_adapter = None try: self.url_adapter = app.create_url_adapter(self.request) except HTTPException as e: self.request.routing_exception = e self.flashes = None self.session = session # Request contexts can be pushed multiple times and interleaved with # other request contexts. Now only if the last level is popped we # get rid of them. Additionally if an application context is missing # one is created implicitly so for each level we add this information self._implicit_app_ctx_stack = [] # indicator if the context was preserved. Next time another context # is pushed the preserved context is popped. self.preserved = False # remembers the exception for pop if there is one in case the context # preservation kicks in. self._preserved_exc = None # Functions that should be executed after the request on the response # object. These will be called before the regular "after_request" # functions. self._after_request_functions = [] @property def g(self): return _app_ctx_stack.top.g @g.setter def g(self, value): _app_ctx_stack.top.g = value def copy(self): """Creates a copy of this request context with the same request object. This can be used to move a request context to a different greenlet. Because the actual request object is the same this cannot be used to move a request context to a different thread unless access to the request object is locked. .. versionadded:: 0.10 .. versionchanged:: 1.1 The current session object is used instead of reloading the original data. This prevents `flask.session` pointing to an out-of-date object. """ return self.__class__( self.app, environ=self.request.environ, request=self.request, session=self.session, ) def match_request(self): """Can be overridden by a subclass to hook into the matching of the request. """ try: result = self.url_adapter.match(return_rule=True) self.request.url_rule, self.request.view_args = result except HTTPException as e: self.request.routing_exception = e def push(self): """Binds the request context to the current context.""" # If an exception occurs in debug mode or if context preservation is # activated under exception situations exactly one context stays # on the stack. The rationale is that you want to access that # information under debug situations. However if someone forgets to # pop that context again we want to make sure that on the next push # it's invalidated, otherwise we run at risk that something leaks # memory. This is usually only a problem in test suite since this # functionality is not active in production environments. top = _request_ctx_stack.top if top is not None and top.preserved: top.pop(top._preserved_exc) # Before we push the request context we have to ensure that there # is an application context. app_ctx = _app_ctx_stack.top if app_ctx is None or app_ctx.app != self.app: app_ctx = self.app.app_context() app_ctx.push() self._implicit_app_ctx_stack.append(app_ctx) else: self._implicit_app_ctx_stack.append(None) if hasattr(sys, "exc_clear"): sys.exc_clear() _request_ctx_stack.push(self) # Open the session at the moment that the request context is available. # This allows a custom open_session method to use the request context. # Only open a new session if this is the first time the request was # pushed, otherwise stream_with_context loses the session. if self.session is None: session_interface = self.app.session_interface self.session = session_interface.open_session(self.app, self.request) if self.session is None: self.session = session_interface.make_null_session(self.app) if self.url_adapter is not None: self.match_request() def pop(self, exc=_sentinel): """Pops the request context and unbinds it by doing that. This will also trigger the execution of functions registered by the :meth:`~flask.Flask.teardown_request` decorator. .. versionchanged:: 0.9 Added the `exc` argument. """ app_ctx = self._implicit_app_ctx_stack.pop() try: clear_request = False if not self._implicit_app_ctx_stack: self.preserved = False self._preserved_exc = None if exc is _sentinel: exc = sys.exc_info()[1] self.app.do_teardown_request(exc) # If this interpreter supports clearing the exception information # we do that now. This will only go into effect on Python 2.x, # on 3.x it disappears automatically at the end of the exception # stack. if hasattr(sys, "exc_clear"): sys.exc_clear() request_close = getattr(self.request, "close", None) if request_close is not None: request_close() clear_request = True finally: rv = _request_ctx_stack.pop() # get rid of circular dependencies at the end of the request # so that we don't require the GC to be active. if clear_request: rv.request.environ["werkzeug.request"] = None # Get rid of the app as well if necessary. if app_ctx is not None: app_ctx.pop(exc) assert rv is self, "Popped wrong request context. (%r instead of %r)" % ( rv, self, ) def auto_pop(self, exc): if self.request.environ.get("flask._preserve_context") or ( exc is not None and self.app.preserve_context_on_exception ): self.preserved = True self._preserved_exc = exc else: self.pop(exc) def __enter__(self): self.push() return self def __exit__(self, exc_type, exc_value, tb): # do not pop the request stack if we are in debug mode and an # exception happened. This will allow the debugger to still # access the request object in the interactive shell. Furthermore # the context can be force kept alive for the test client. # See flask.testing for how this works. self.auto_pop(exc_value) if BROKEN_PYPY_CTXMGR_EXIT and exc_type is not None: reraise(exc_type, exc_value, tb) def __repr__(self): return "<%s '%s' [%s] of %s>" % ( self.__class__.__name__, self.request.url, self.request.method, self.app.name, )
这个接收的参数其中有app对象（Flask类）、environ（请求相关信息）等。
def __init__(self, app, environ, request=None, session=None): self.app = app if request is None: #刚开始request是None request = app.request_class(environ) self.request = request self.url_adapter = None try: self.url_adapter = app.create_url_adapter(self.request) except HTTPException as e: self.request.routing_exception = e self.flashes = None self.session = session
请求刚进来，request参数是None，所以执行app.request_class：
class Flask(_PackageBoundObject): #: The class that is used for request objects. See :class:`~flask.Request` #: for more information. request_class = Request #from .wrappers import Request
对请求的字符串信息进行处理，返回Request对象，并且将Request对象封装到RequestContext类中。
（四）Request类
class Request(RequestBase, JSONMixin): """The request object used by default in Flask. Remembers the matched endpoint and view arguments. It is what ends up as :class:`~flask.request`. If you want to replace the request object used you can subclass this and set :attr:`~flask.Flask.request_class` to your subclass. The request object is a :class:`~werkzeug.wrappers.Request` subclass and provides all of the attributes Werkzeug defines plus a few Flask specific ones. """ #: The internal URL rule that matched the request. This can be #: useful to inspect which methods are allowed for the URL from #: a before/after handler (``request.url_rule.methods``) etc. #: Though if the request's method was invalid for the URL rule, #: the valid list is available in ``routing_exception.valid_methods`` #: instead (an attribute of the Werkzeug exception #: :exc:`~werkzeug.exceptions.MethodNotAllowed`) #: because the request was never internally bound. #: #: .. versionadded:: 0.6 url_rule = None #: A dict of view arguments that matched the request. If an exception #: happened when matching, this will be ``None``. view_args = None #: If matching the URL failed, this is the exception that will be #: raised / was raised as part of the request handling. This is #: usually a :exc:`~werkzeug.exceptions.NotFound` exception or #: something similar. routing_exception = None @property def max_content_length(self): """Read-only view of the ``MAX_CONTENT_LENGTH`` config key.""" if current_app: return current_app.config["MAX_CONTENT_LENGTH"] @property def endpoint(self): """The endpoint that matched the request. This in combination with :attr:`view_args` can be used to reconstruct the same or a modified URL. If an exception happened when matching, this will be ``None``. """ if self.url_rule is not None: return self.url_rule.endpoint @property def blueprint(self): """The name of the current blueprint""" if self.url_rule and "." in self.url_rule.endpoint: return self.url_rule.endpoint.rsplit(".", 1)[0] def _load_form_data(self): RequestBase._load_form_data(self) # In debug mode we're replacing the files multidict with an ad-hoc # subclass that raises a different error for key errors. if ( current_app and current_app.debug and self.mimetype != "multipart/form-data" and not self.files ): from .debughelpers import attach_enctype_error_multidict attach_enctype_error_multidict(self)
RequestContext封装就是这个类的对象，这个类的基类BaseRequest初始化时接收了environ，并且对请求字符串进行处理。
class BaseRequest(object): """Very basic request object. This does not implement advanced stuff like entity tag parsing or cache controls. The request object is created with the WSGI environment as first argument and will add itself to the WSGI environment as ``'werkzeug.request'`` unless it's created with `populate_request` set to False. There are a couple of mixins available that add additional functionality to the request object, there is also a class called `Request` which subclasses `BaseRequest` and all the important mixins. It's a good idea to create a custom subclass of the :class:`BaseRequest` and add missing functionality either via mixins or direct implementation. Here an example for such subclasses:: from werkzeug.wrappers import BaseRequest, ETagRequestMixin class Request(BaseRequest, ETagRequestMixin): pass Request objects are **read only**. As of 0.5 modifications are not allowed in any place. Unlike the lower level parsing functions the request object will use immutable objects everywhere possible. Per default the request object will assume all the text data is `utf-8` encoded. Please refer to :doc:`the unicode chapter </unicode>` for more details about customizing the behavior. Per default the request object will be added to the WSGI environment as `werkzeug.request` to support the debugging system. If you don't want that, set `populate_request` to `False`. If `shallow` is `True` the environment is initialized as shallow object around the environ. Every operation that would modify the environ in any way (such as consuming form data) raises an exception unless the `shallow` attribute is explicitly set to `False`. This is useful for middlewares where you don't want to consume the form data by accident. A shallow request is not populated to the WSGI environment. .. versionchanged:: 0.5 read-only mode was enforced by using immutables classes for all data. """ #: the charset for the request, defaults to utf-8 charset = "utf-8" #: the error handling procedure for errors, defaults to 'replace' encoding_errors = "replace" #: the maximum content length. This is forwarded to the form data #: parsing function (:func:`parse_form_data`). When set and the #: :attr:`form` or :attr:`files` attribute is accessed and the #: parsing fails because more than the specified value is transmitted #: a :exc:`~werkzeug.exceptions.RequestEntityTooLarge` exception is raised. #: #: Have a look at :ref:`dealing-with-request-data` for more details. #: #: .. versionadded:: 0.5 max_content_length = None #: the maximum form field size. This is forwarded to the form data #: parsing function (:func:`parse_form_data`). When set and the #: :attr:`form` or :attr:`files` attribute is accessed and the #: data in memory for post data is longer than the specified value a #: :exc:`~werkzeug.exceptions.RequestEntityTooLarge` exception is raised. #: #: Have a look at :ref:`dealing-with-request-data` for more details. #: #: .. versionadded:: 0.5 max_form_memory_size = None #: the class to use for `args` and `form`. The default is an #: :class:`~werkzeug.datastructures.ImmutableMultiDict` which supports #: multiple values per key. alternatively it makes sense to use an #: :class:`~werkzeug.datastructures.ImmutableOrderedMultiDict` which #: preserves order or a :class:`~werkzeug.datastructures.ImmutableDict` #: which is the fastest but only remembers the last key. It is also #: possible to use mutable structures, but this is not recommended. #: #: .. versionadded:: 0.6 parameter_storage_class = ImmutableMultiDict #: the type to be used for list values from the incoming WSGI environment. #: By default an :class:`~werkzeug.datastructures.ImmutableList` is used #: (for example for :attr:`access_list`). #: #: .. versionadded:: 0.6 list_storage_class = ImmutableList #: The type to be used for dict values from the incoming WSGI #: environment. (For example for :attr:`cookies`.) By default an #: :class:`~werkzeug.datastructures.ImmutableMultiDict` is used. #: #: .. versionchanged:: 1.0.0 #: Changed to ``ImmutableMultiDict`` to support multiple values. #: #: .. versionadded:: 0.6 dict_storage_class = ImmutableMultiDict #: The form data parser that shoud be used. Can be replaced to customize #: the form date parsing. form_data_parser_class = FormDataParser #: Optionally a list of hosts that is trusted by this request. By default #: all hosts are trusted which means that whatever the client sends the #: host is will be accepted. #: #: Because `Host` and `X-Forwarded-Host` headers can be set to any value by #: a malicious client, it is recommended to either set this property or #: implement similar validation in the proxy (if application is being run #: behind one). #: #: .. versionadded:: 0.9 trusted_hosts = None #: Indicates whether the data descriptor should be allowed to read and #: buffer up the input stream. By default it's enabled. #: #: .. versionadded:: 0.9 disable_data_descriptor = False def __init__(self, environ, populate_request=True, shallow=False): self.environ = environ if populate_request and not shallow: self.environ["werkzeug.request"] = self self.shallow = shallow def __repr__(self): # make sure the __repr__ even works if the request was created # from an invalid WSGI environment. If we display the request # in a debug session we don't want the repr to blow up. args = [] try: args.append("'%s'" % to_native(self.url, self.url_charset)) args.append("[%s]" % self.method) except Exception: args.append("(invalid WSGI environ)") return "<%s %s>" % (self.__class__.__name__, " ".join(args)) @property def url_charset(self): """The charset that is assumed for URLs. Defaults to the value of :attr:`charset`. .. versionadded:: 0.6 """ return self.charset @classmethod def from_values(cls, *args, **kwargs): """Create a new request object based on the values provided. If environ is given missing values are filled from there. This method is useful for small scripts when you need to simulate a request from an URL. Do not use this method for unittesting, there is a full featured client object (:class:`Client`) that allows to create multipart requests, support for cookies etc. This accepts the same options as the :class:`~werkzeug.test.EnvironBuilder`. .. versionchanged:: 0.5 This method now accepts the same arguments as :class:`~werkzeug.test.EnvironBuilder`. Because of this the `environ` parameter is now called `environ_overrides`. :return: request object """ from ..test import EnvironBuilder charset = kwargs.pop("charset", cls.charset) kwargs["charset"] = charset builder = EnvironBuilder(*args, **kwargs) try: return builder.get_request(cls) finally: builder.close() @classmethod def application(cls, f): """Decorate a function as responder that accepts the request as the last argument. This works like the :func:`responder` decorator but the function is passed the request object as the last argument and the request object will be closed automatically:: @Request.application def my_wsgi_app(request): return Response('Hello World!') As of Werkzeug 0.14 HTTP exceptions are automatically caught and converted to responses instead of failing. :param f: the WSGI callable to decorate :return: a new WSGI callable """ #: return a callable that wraps the -2nd argument with the request #: and calls the function with all the arguments up to that one and #: the request. The return value is then called with the latest #: two arguments. This makes it possible to use this decorator for #: both standalone WSGI functions as well as bound methods and #: partially applied functions. from ..exceptions import HTTPException def application(*args): request = cls(args[-2]) with request: try: resp = f(*args[:-2] + (request,)) except HTTPException as e: resp = e.get_response(args[-2]) return resp(*args[-2:]) return update_wrapper(application, f) def _get_file_stream( self, total_content_length, content_type, filename=None, content_length=None ): """Called to get a stream for the file upload. This must provide a file-like class with `read()`, `readline()` and `seek()` methods that is both writeable and readable. The default implementation returns a temporary file if the total content length is higher than 500KB. Because many browsers do not provide a content length for the files only the total content length matters. :param total_content_length: the total content length of all the data in the request combined. This value is guaranteed to be there. :param content_type: the mimetype of the uploaded file. :param filename: the filename of the uploaded file. May be `None`. :param content_length: the length of this file. This value is usually not provided because webbrowsers do not provide this value. """ return default_stream_factory( total_content_length=total_content_length, filename=filename, content_type=content_type, content_length=content_length, ) @property def want_form_data_parsed(self): """Returns True if the request method carries content. As of Werkzeug 0.9 this will be the case if a content type is transmitted. .. versionadded:: 0.8 """ return bool(self.environ.get("CONTENT_TYPE")) def make_form_data_parser(self): """Creates the form data parser. Instantiates the :attr:`form_data_parser_class` with some parameters. .. versionadded:: 0.8 """ return self.form_data_parser_class( self._get_file_stream, self.charset, self.encoding_errors, self.max_form_memory_size, self.max_content_length, self.parameter_storage_class, ) def _load_form_data(self): """Method used internally to retrieve submitted data. After calling this sets `form` and `files` on the request object to multi dicts filled with the incoming form data. As a matter of fact the input stream will be empty afterwards. You can also call this method to force the parsing of the form data. .. versionadded:: 0.8 """ # abort early if we have already consumed the stream if "form" in self.__dict__: return _assert_not_shallow(self) if self.want_form_data_parsed: content_type = self.environ.get("CONTENT_TYPE", "") content_length = get_content_length(self.environ) mimetype, options = parse_options_header(content_type) parser = self.make_form_data_parser() data = parser.parse( self._get_stream_for_parsing(), mimetype, content_length, options ) else: data = ( self.stream, self.parameter_storage_class(), self.parameter_storage_class(), ) # inject the values into the instance dict so that we bypass # our cached_property non-data descriptor. d = self.__dict__ d["stream"], d["form"], d["files"] = data def _get_stream_for_parsing(self): """This is the same as accessing :attr:`stream` with the difference that if it finds cached data from calling :meth:`get_data` first it will create a new stream out of the cached data. .. versionadded:: 0.9.3 """ cached_data = getattr(self, "_cached_data", None) if cached_data is not None: return BytesIO(cached_data) return self.stream def close(self): """Closes associated resources of this request object. This closes all file handles explicitly. You can also use the request object in a with statement which will automatically close it. .. versionadded:: 0.9 """ files = self.__dict__.get("files") for _key, value in iter_multi_items(files or ()): value.close() def __enter__(self): return self def __exit__(self, exc_type, exc_value, tb): self.close() @cached_property def stream(self): """ If the incoming form data was not encoded with a known mimetype the data is stored unmodified in this stream for consumption. Most of the time it is a better idea to use :attr:`data` which will give you that data as a string. The stream only returns the data once. Unlike :attr:`input_stream` this stream is properly guarded that you can't accidentally read past the length of the input. Werkzeug will internally always refer to this stream to read data which makes it possible to wrap this object with a stream that does filtering. .. versionchanged:: 0.9 This stream is now always available but might be consumed by the form parser later on. Previously the stream was only set if no parsing happened. """ _assert_not_shallow(self) return get_input_stream(self.environ) input_stream = environ_property( "wsgi.input", """The WSGI input stream. In general it's a bad idea to use this one because you can easily read past the boundary. Use the :attr:`stream` instead.""", ) @cached_property def args(self): """The parsed URL parameters (the part in the URL after the question mark). By default an :class:`~werkzeug.datastructures.ImmutableMultiDict` is returned from this function. This can be changed by setting :attr:`parameter_storage_class` to a different type. This might be necessary if the order of the form data is important. """ return url_decode( wsgi_get_bytes(self.environ.get("QUERY_STRING", "")), self.url_charset, errors=self.encoding_errors, cls=self.parameter_storage_class, ) @cached_property def data(self): """ Contains the incoming request data as string in case it came with a mimetype Werkzeug does not handle. """ if self.disable_data_descriptor: raise AttributeError("data descriptor is disabled") # XXX: this should eventually be deprecated. # We trigger form data parsing first which means that the descriptor # will not cache the data that would otherwise be .form or .files # data. This restores the behavior that was there in Werkzeug # before 0.9. New code should use :meth:`get_data` explicitly as # this will make behavior explicit. return self.get_data(parse_form_data=True) def get_data(self, cache=True, as_text=False, parse_form_data=False): """This reads the buffered incoming data from the client into one bytestring. By default this is cached but that behavior can be changed by setting `cache` to `False`. Usually it's a bad idea to call this method without checking the content length first as a client could send dozens of megabytes or more to cause memory problems on the server. Note that if the form data was already parsed this method will not return anything as form data parsing does not cache the data like this method does. To implicitly invoke form data parsing function set `parse_form_data` to `True`. When this is done the return value of this method will be an empty string if the form parser handles the data. This generally is not necessary as if the whole data is cached (which is the default) the form parser will used the cached data to parse the form data. Please be generally aware of checking the content length first in any case before calling this method to avoid exhausting server memory. If `as_text` is set to `True` the return value will be a decoded unicode string. .. versionadded:: 0.9 """ rv = getattr(self, "_cached_data", None) if rv is None: if parse_form_data: self._load_form_data() rv = self.stream.read() if cache: self._cached_data = rv if as_text: rv = rv.decode(self.charset, self.encoding_errors) return rv @cached_property def form(self): """The form parameters. By default an :class:`~werkzeug.datastructures.ImmutableMultiDict` is returned from this function. This can be changed by setting :attr:`parameter_storage_class` to a different type. This might be necessary if the order of the form data is important. Please keep in mind that file uploads will not end up here, but instead in the :attr:`files` attribute. .. versionchanged:: 0.9 Previous to Werkzeug 0.9 this would only contain form data for POST and PUT requests. """ self._load_form_data() return self.form @cached_property def values(self): """A :class:`werkzeug.datastructures.CombinedMultiDict` that combines :attr:`args` and :attr:`form`.""" args = [] for d in self.args, self.form: if not isinstance(d, MultiDict): d = MultiDict(d) args.append(d) return CombinedMultiDict(args) @cached_property def files(self): """:class:`~werkzeug.datastructures.MultiDict` object containing all uploaded files. Each key in :attr:`files` is the name from the ``<input type="file" name="">``. Each value in :attr:`files` is a Werkzeug :class:`~werkzeug.datastructures.FileStorage` object. It basically behaves like a standard file object you know from Python, with the difference that it also has a :meth:`~werkzeug.datastructures.FileStorage.save` function that can store the file on the filesystem. Note that :attr:`files` will only contain data if the request method was POST, PUT or PATCH and the ``<form>`` that posted to the request had ``enctype="multipart/form-data"``. It will be empty otherwise. See the :class:`~werkzeug.datastructures.MultiDict` / :class:`~werkzeug.datastructures.FileStorage` documentation for more details about the used data structure. """ self._load_form_data() return self.files @cached_property def cookies(self): """A :class:`dict` with the contents of all cookies transmitted with the request.""" return parse_cookie( self.environ, self.charset, self.encoding_errors, cls=self.dict_storage_class, ) @cached_property def headers(self): """The headers from the WSGI environ as immutable :class:`~werkzeug.datastructures.EnvironHeaders`. """ return EnvironHeaders(self.environ) @cached_property def path(self): """Requested path as unicode. This works a bit like the regular path info in the WSGI environment but will always include a leading slash, even if the URL root is accessed. """ raw_path = wsgi_decoding_dance( self.environ.get("PATH_INFO") or "", self.charset, self.encoding_errors ) return "/" + raw_path.lstrip("/") @cached_property def full_path(self): """Requested path as unicode, including the query string.""" return self.path + u"?" + to_unicode(self.query_string, self.url_charset) @cached_property def script_root(self): """The root path of the script without the trailing slash.""" raw_path = wsgi_decoding_dance( self.environ.get("SCRIPT_NAME") or "", self.charset, self.encoding_errors ) return raw_path.rstrip("/") @cached_property def url(self): """The reconstructed current URL as IRI. See also: :attr:`trusted_hosts`. """ return get_current_url(self.environ, trusted_hosts=self.trusted_hosts) @cached_property def base_url(self): """Like :attr:`url` but without the querystring See also: :attr:`trusted_hosts`. """ return get_current_url( self.environ, strip_querystring=True, trusted_hosts=self.trusted_hosts ) @cached_property def url_root(self): """The full URL root (with hostname), this is the application root as IRI. See also: :attr:`trusted_hosts`. """ return get_current_url(self.environ, True, trusted_hosts=self.trusted_hosts) @cached_property def host_url(self): """Just the host with scheme as IRI. See also: :attr:`trusted_hosts`. """ return get_current_url( self.environ, host_only=True, trusted_hosts=self.trusted_hosts ) @cached_property def host(self): """Just the host including the port if available. See also: :attr:`trusted_hosts`. """ return get_host(self.environ, trusted_hosts=self.trusted_hosts) query_string = environ_property( "QUERY_STRING", "", read_only=True, load_func=wsgi_get_bytes, doc="The URL parameters as raw bytestring.", ) method = environ_property( "REQUEST_METHOD", "GET", read_only=True, load_func=lambda x: x.upper(), doc="The request method. (For example ``'GET'`` or ``'POST'``).", ) @cached_property def access_route(self): """If a forwarded header exists this is a list of all ip addresses from the client ip to the last proxy server. """ if "HTTP_X_FORWARDED_FOR" in self.environ: return self.list_storage_class( parse_list_header(self.environ["HTTP_X_FORWARDED_FOR"]) ) elif "REMOTE_ADDR" in self.environ: return self.list_storage_class([self.environ["REMOTE_ADDR"]]) return self.list_storage_class() @property def remote_addr(self): """The remote address of the client.""" return self.environ.get("REMOTE_ADDR") remote_user = environ_property( "REMOTE_USER", doc="""If the server supports user authentication, and the script is protected, this attribute contains the username the user has authenticated as.""", ) scheme = environ_property( "wsgi.url_scheme", doc=""" URL scheme (http or https). .. versionadded:: 0.7""", ) is_secure = property( lambda self: self.environ["wsgi.url_scheme"] == "https", doc="`True` if the request is secure.", ) is_multithread = environ_property( "wsgi.multithread", doc="""boolean that is `True` if the application is served by a multithreaded WSGI server.""", ) is_multiprocess = environ_property( "wsgi.multiprocess", doc="""boolean that is `True` if the application is served by a WSGI server that spawns multiple processes.""", ) is_run_once = environ_property( "wsgi.run_once", doc="""boolean that is `True` if the application will be executed only once in a process lifetime. This is the case for CGI for example, but it's not guaranteed that the execution only happens one time.""", )
（五）LocalStack类
这个类是做什么的呢？上面已经将封装请求RequestContext对象得到，这个类就是将请求保存在Local对象中。
class LocalStack(object): """This class works similar to a :class:`Local` but keeps a stack of objects instead. This is best explained with an example:: >>> ls = LocalStack() >>> ls.push(42) >>> ls.top 42 >>> ls.push(23) >>> ls.top 23 >>> ls.pop() 23 >>> ls.top 42 They can be force released by using a :class:`LocalManager` or with the :func:`release_local` function but the correct way is to pop the item from the stack after using. When the stack is empty it will no longer be bound to the current context (and as such released). By calling the stack without arguments it returns a proxy that resolves to the topmost item on the stack. .. versionadded:: 0.6.1 """ def __init__(self): self._local = Local() def __release_local__(self): self._local.__release_local__() @property def __ident_func__(self): return self._local.__ident_func__ @__ident_func__.setter def __ident_func__(self, value): object.__setattr__(self._local, "__ident_func__", value) def __call__(self): def _lookup(): rv = self.top if rv is None: raise RuntimeError("object unbound") return rv return LocalProxy(_lookup) def push(self, obj): """Pushes a new item to the stack""" rv = getattr(self._local, "stack", None) if rv is None: self._local.stack = rv = [] rv.append(obj) return rv def pop(self): """Removes the topmost item from the stack, will return the old value or `None` if the stack was already empty. """ stack = getattr(self._local, "stack", None) if stack is None: return None elif len(stack) == 1: release_local(self._local) return stack[-1] else: return stack.pop() @property def top(self): """The topmost item on the stack. If the stack is empty, `None` is returned. """ try: return self._local.stack[-1] except (AttributeError, IndexError): return None
class LocalStack(object): def push(self, obj): """Pushes a new item to the stack""" rv = getattr(self._local, "stack", None) if rv is None: self._local.stack = rv = [] rv.append(obj) return rv
其中obj就是RequestContext，self._local 就是Local对象。最后Local对象得到的就是类似这样的东西：
”“” { 2651:{'stack':[obj]} ... } “”“
最后移除这个对象通过这个类中pop来实现。
（六）LocalProxy类
@implements_bool class LocalProxy(object): """Acts as a proxy for a werkzeug local. Forwards all operations to a proxied object. The only operations not supported for forwarding are right handed operands and any kind of assignment. Example usage:: from werkzeug.local import Local l = Local() # these are proxies request = l('request') user = l('user') from werkzeug.local import LocalStack _response_local = LocalStack() # this is a proxy response = _response_local() Whenever something is bound to l.user / l.request the proxy objects will forward all operations. If no object is bound a :exc:`RuntimeError` will be raised. To create proxies to :class:`Local` or :class:`LocalStack` objects, call the object as shown above. If you want to have a proxy to an object looked up by a function, you can (as of Werkzeug 0.6.1) pass a function to the :class:`LocalProxy` constructor:: session = LocalProxy(lambda: get_current_request().session) .. versionchanged:: 0.6.1 The class can be instantiated with a callable as well now. """ __slots__ = ("__local", "__dict__", "__name__", "__wrapped__") def __init__(self, local, name=None): object.__setattr__(self, "_LocalProxy__local", local) object.__setattr__(self, "__name__", name) if callable(local) and not hasattr(local, "__release_local__"): # "local" is a callable that is not an instance of Local or # LocalManager: mark it as a wrapped function. object.__setattr__(self, "__wrapped__", local) def _get_current_object(self): """Return the current object. This is useful if you want the real object behind the proxy at a time for performance reasons or because you want to pass the object into a different context. """ if not hasattr(self.__local, "__release_local__"): return self.__local() try: return getattr(self.__local, self.__name__) except AttributeError: raise RuntimeError("no object bound to %s" % self.__name__) @property def __dict__(self): try: return self._get_current_object().__dict__ except RuntimeError: raise AttributeError("__dict__") def __repr__(self): try: obj = self._get_current_object() except RuntimeError: return "<%s unbound>" % self.__class__.__name__ return repr(obj) def __bool__(self): try: return bool(self._get_current_object()) except RuntimeError: return False def __unicode__(self): try: return unicode(self._get_current_object()) # noqa except RuntimeError: return repr(self) def __dir__(self): try: return dir(self._get_current_object()) except RuntimeError: return [] def __getattr__(self, name): if name == "__members__": return dir(self._get_current_object()) return getattr(self._get_current_object(), name) def __setitem__(self, key, value): self._get_current_object()[key] = value def __delitem__(self, key): del self._get_current_object()[key] if PY2: __getslice__ = lambda x, i, j: x._get_current_object()[i:j] def __setslice__(self, i, j, seq): self._get_current_object()[i:j] = seq def __delslice__(self, i, j): del self._get_current_object()[i:j] __setattr__ = lambda x, n, v: setattr(x._get_current_object(), n, v) __delattr__ = lambda x, n: delattr(x._get_current_object(), n) __str__ = lambda x: str(x._get_current_object()) __lt__ = lambda x, o: x._get_current_object() < o __le__ = lambda x, o: x._get_current_object() <= o __eq__ = lambda x, o: x._get_current_object() == o __ne__ = lambda x, o: x._get_current_object() != o __gt__ = lambda x, o: x._get_current_object() > o __ge__ = lambda x, o: x._get_current_object() >= o __cmp__ = lambda x, o: cmp(x._get_current_object(), o) # noqa __hash__ = lambda x: hash(x._get_current_object()) __call__ = lambda x, *a, **kw: x._get_current_object()(*a, **kw) __len__ = lambda x: len(x._get_current_object()) __getitem__ = lambda x, i: x._get_current_object()[i] __iter__ = lambda x: iter(x._get_current_object()) __contains__ = lambda x, i: i in x._get_current_object() __add__ = lambda x, o: x._get_current_object() + o __sub__ = lambda x, o: x._get_current_object() - o __mul__ = lambda x, o: x._get_current_object() * o __floordiv__ = lambda x, o: x._get_current_object() // o __mod__ = lambda x, o: x._get_current_object() % o __divmod__ = lambda x, o: x._get_current_object().__divmod__(o) __pow__ = lambda x, o: x._get_current_object() ** o __lshift__ = lambda x, o: x._get_current_object() << o __rshift__ = lambda x, o: x._get_current_object() >> o __and__ = lambda x, o: x._get_current_object() & o __xor__ = lambda x, o: x._get_current_object() ^ o __or__ = lambda x, o: x._get_current_object() | o __div__ = lambda x, o: x._get_current_object().__div__(o) __truediv__ = lambda x, o: x._get_current_object().__truediv__(o) __neg__ = lambda x: -(x._get_current_object()) __pos__ = lambda x: +(x._get_current_object()) __abs__ = lambda x: abs(x._get_current_object()) __invert__ = lambda x: ~(x._get_current_object()) __complex__ = lambda x: complex(x._get_current_object()) __int__ = lambda x: int(x._get_current_object()) __long__ = lambda x: long(x._get_current_object()) # noqa __float__ = lambda x: float(x._get_current_object()) __oct__ = lambda x: oct(x._get_current_object()) __hex__ = lambda x: hex(x._get_current_object()) __index__ = lambda x: x._get_current_object().__index__() __coerce__ = lambda x, o: x._get_current_object().__coerce__(x, o) __enter__ = lambda x: x._get_current_object().__enter__() __exit__ = lambda x, *a, **kw: x._get_current_object().__exit__(*a, **kw) __radd__ = lambda x, o: o + x._get_current_object() __rsub__ = lambda x, o: o - x._get_current_object() __rmul__ = lambda x, o: o * x._get_current_object() __rdiv__ = lambda x, o: o / x._get_current_object() if PY2: __rtruediv__ = lambda x, o: x._get_current_object().__rtruediv__(o) else: __rtruediv__ = __rdiv__ __rfloordiv__ = lambda x, o: o // x._get_current_object() __rmod__ = lambda x, o: o % x._get_current_object() __rdivmod__ = lambda x, o: x._get_current_object().__rdivmod__(o) __copy__ = lambda x: copy.copy(x._get_current_object()) __deepcopy__ = lambda x, memo: copy.deepcopy(x._get_current_object(), memo)
我们在flask中导入request对象，实际上就是LocalProxy类的对象：
request = LocalProxy(partial(_lookup_req_object, "request"))
显request操作方面就是和这个类有关，比如：在视图函数中进行request.method获取当前请求的方法，那么就会调用LocalProxy这个类中的__getattr__方法：
def __getattr__(self, name): if name == "__members__": return dir(self._get_current_object()) return getattr(self._get_current_object(), name)
返回的是getattr(self._get_current_object(), name) ，那么_get_current_object()和name分别是是什么呢？
def _get_current_object(self): """Return the current object. This is useful if you want the real object behind the proxy at a time for performance reasons or because you want to pass the object into a different context. """ if not hasattr(self.__local, "__release_local__"): return self.__local() try: return getattr(self.__local, self.__name__) except AttributeError: raise RuntimeError("no object bound to %s" % self.__name__)
在进行这个之前，先执行传入LocalProxy的偏函数：
def _lookup_req_object(name): top = _request_ctx_stack.top #获取Local对象中添加的RequestContext对象 if top is None: raise RuntimeError(_request_ctx_err_msg) return getattr(top, name)
所以getattr(self.__local, self.__name__)中self.__local是RequestContext对象，__name__就是‘request'字符串。这样就获取到了Request对象。从而得到request.method的值。
三、类之间的关系
那么这六个类之间又是如何进行关联呢？
可以通过一个简单的图将之间的关系表示出来。
作者：iveBoy
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须在文章页面给出原文连接，否则保留追究法律责任的权利。
