Flask之请求钩子的实现

请求钩子

通过装饰器为一个模块添加请求钩子, 对当前模块的请求进行额外的处理. 比如权限验证.

说白了，就是在执行视图函数前后你可以进行一些处理，Flask使用装饰器为我们提供了注册通用函数的功能。

1、before_first_request:在处理第一个请求前执行

before_first_request

在对应用程序实例的第一个请求之前注册要运行的函数, 只会执行一次

  #: A lists of functions that should be called at the beginning of the  #: first request to this instance. To register a function here, use  #: the :meth:`before_first_request` decorator.  #:  #: .. versionadded:: 0.8  self.before_first_request_funcs = []  @setupmethod  def before_first_request(self, f):    """Registers a function to be run before the first request to this    instance of the application.    .. versionadded:: 0.8    """    self.before_first_request_funcs.append(f) 

将要运行的函数存放到before_first_request_funcs 属性中进行保存

2、before_request:在每次请求前执行

在每个请求之前注册一个要运行的函数, 每一次请求都会执行

  #: A dictionary with lists of functions that should be called at the  #: beginning of the 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 open database connections or  #: getting hold of the currently logged in user. To register a  #: function here, use the :meth:`before_request` decorator.  self.before_request_funcs = {}   @setupmethod  def before_request(self, f):    """Registers a function to run before each request."""    self.before_request_funcs.setdefault(None, []).append(f)    return f

将要运行的函数存放在字典中, None 为键的列表中存放的是整个应用的所有请求都要运行的函数.

3、after_request:每次请求之后调用，前提是没有未处理的异常抛出

在每个请求之后注册一个要运行的函数, 每次请求都会执行. 需要接收一个 Response 类的对象作为参数 并返回一个新的Response 对象 或者 直接返回接受到的Response 对象

  #: 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 open database connections or getting hold of the  #: currently logged in user. To register a function here, use the  #: :meth:`after_request` decorator.  self.after_request_funcs = {}  @setupmethod  def after_request(self, f):    """Register a function to be run after each request. Your function    must take one parameter, a :attr:`response_class` object and return    a new response object or the same (see :meth:`process_response`).    As of Flask 0.7 this function might not be executed at the end of the    request in case an unhandled exception occurred.    """    self.after_request_funcs.setdefault(None, []).append(f)    return f