Flask框架整个流程源码解读

    def wsgi_app(self, environ, start_response):
        #1.ctx是ResquestContext的对象，里面request
        ctx = self.request_context(environ)
        error = None
        try:
            try:
                 #2.就是ctx放到了Local对象
                ctx.push()
                #3.所有请求的执行函数的，包括请求扩展，真正的视图函数
                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
             #3. 请求之后的函数
            return response(environ, start_response)
        finally:
            if self.should_ignore_error(error):
                error = None
            #4.最后把对应的request在request的队列中删除
            ctx.auto_pop(error)

 1.1RequestContext(self, environ) self ,是app对象 environ,请求相关的
        1.2 RequestContext在实例化的时候的源码：
        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
            self._implicit_app_ctx_stack = []
            self.preserved = False
            self._after_request_functions = []
#这个RequestContext对象封装了,request 和seesoin

 def push(self):
        #_request_ctx_stack是localStack的对象
        #self是ctx,把self也就ctx放入到local对象里面
        top = _request_ctx_stack.top
        if top is not None and top.preserved:
            top.pop(top._preserved_exc)
        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)  #这个里面的push源码如下
        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()

     #obj是ctx
    def push(self, obj):
        #obj是ctx,requestContext的对象
        rv = getattr(self._local, "stack", None)
        if rv is None:
            self._local.stack = rv = []
        rv.append(obj)
        return rv
'''
        2.1.1 _request_ctx_stack.push(self)现在的self是ctx
        2.1.2 _request_ctx_stack是LocalStack()的对象
        2.1.3 LocalStack()的push把ctx传过来
        2.1.4 LocalStack()的push方法
        最终也就是ctx.push()他的最终目的：把当前的ctx放入到Local()里面     
'''    

     #这是服务器第一次请求时候执行的函数
            self.try_trigger_before_first_request_functions()
            try:
                request_started.send(self)
                #执行请求之前所有的函数，并且拿到请求之前的返回值
                rv = self.preprocess_request()
                if rv is None:
                    #这个是真正视图函数，如果我的请求之前函数没有返回值才会执行
                    rv = self.dispatch_request()
            except Exception as e:
                rv = self.handle_user_exception(e)
            return self.finalize_request(rv)
    3.1 return self.finalize_request(rv)的源码：
        def finalize_request(self, rv, from_error_handler=False):
            response = self.make_response(rv)
            try:
                #请求之后的函数，after_request
                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

  4.1 我们在flask导入request,这个request是一个全局的变量，我们怎么通过request区分我当前的request对象(environ)
     我们发现request是LocalProxy的对象
    4.2 当我们用全局的request.属性的时候，就会去找LocalProxy的对象，但是我们发现里面根本就没有
        那他一定执行LocalProxy对象的__getattr__方法
    4.3 我们现在来看LocalProxy对象的__getattr__方法的源码：
        #name我们要获取属性名
        def __getattr__(self, name):
            if name == "__members__":
                return dir(self._get_current_object())
            #form
            #self._get_current_object()就是ctx里面的request，
            return getattr(self._get_current_object(), name)
        4.3.1 通过反射self._get_current_object()对象，来找我们属性，也就是name
           self._get_current_object()的源码：
                def _get_current_object(self):
                    if not hasattr(self.__local, "__release_local__"):
                        return self.__local()
                    try:
                        #self.__local就实例化传过来的偏函数,
                        return getattr(self.__local, self.__name__)
                    except AttributeError:
                        raise RuntimeError("no object bound to %s" % self.__name__)

           4.3.1.1 return getattr(self.__local, self.__name__)那这里self.__local是谁？
                    def __init__(self, local, name=None):
                          object.__setattr__(self, "_LocalProxy__local", local)
                    self.___local为local
                    这个local为实例化的时候传的
                4.3.1.1.1 这个实例化的时候的操作
                   request = LocalProxy(partial(_lookup_req_object, "request"))
                   4.3.1.1的local就是 partial(_lookup_req_object, "request")的地址
                4.3.1.1.2 _lookup_req_object的源码：
                    #调用的时候 partial(_lookup_req_object, "request")
                    #现在的name就是"request"
                    def _lookup_req_object(name):
                        # top是当前线程的ctx
                        top = _request_ctx_stack.top
                        if top is None:
                            raise RuntimeError(_request_ctx_err_msg)
                        #找top里面的request
                        # ctx找request
                        return getattr(top, name)
                4.3.1.1.2 我们来看这个_request_ctx_stack.top的top方法
                        def top(self):
                            try:
                                return self._local.stack[-1]
                            except (AttributeError, IndexError):
                                return None
                        我们发现这个self._local是Local()对象,这样就把ctx拿到了