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Flask之請求鉤子的實(shí)現(xiàn)

更新時(shí)間：2018年12月23日 10:21:31 作者：二十一

這篇文章主要介紹了Flask之請求鉤子的實(shí)現(xiàn)，文中通過示例代碼介紹的非常詳細(xì)，對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來一起學(xué)習(xí)學(xué)習(xí)吧

請求鉤子

通過裝飾器為一個(gè)模塊添加請求鉤子, 對當(dāng)前模塊的請求進(jìn)行額外的處理. 比如權(quán)限驗(yàn)證.

說白了，就是在執(zhí)行視圖函數(shù)前后你可以進(jìn)行一些處理，F(xiàn)lask使用裝飾器為我們提供了注冊通用函數(shù)的功能。

1、before_first_request:在處理第一個(gè)請求前執(zhí)行

before_first_request

在對應(yīng)用程序?qū)嵗牡谝粋€(gè)請求之前注冊要運(yùn)行的函數(shù), 只會執(zhí)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)

將要運(yùn)行的函數(shù)存放到before_first_request_funcs 屬性中進(jìn)行保存

2、before_request:在每次請求前執(zhí)行

在每個(gè)請求之前注冊一個(gè)要運(yùn)行的函數(shù), 每一次請求都會執(zhí)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

將要運(yùn)行的函數(shù)存放在字典中, None 為鍵的列表中存放的是整個(gè)應(yīng)用的所有請求都要運(yùn)行的函數(shù).

3、after_request:每次請求之后調(diào)用，前提是沒有未處理的異常拋出

在每個(gè)請求之后注冊一個(gè)要運(yùn)行的函數(shù), 每次請求都會執(zhí)行. 需要接收一個(gè) Response 類的對象作為參數(shù) 并返回一個(gè)新的Response 對象或者直接返回接受到的Response 對象

  #: 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

4、teardown_request:每次請求之后調(diào)用，即使有未處理的異常拋出

注冊一個(gè)函數(shù)在每個(gè)請求的末尾運(yùn)行，不管是否有異常, 每次請求的最后都會執(zhí)行.

  #: 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 = {}

  @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.
    """
    self.teardown_request_funcs.setdefault(None, []).append(f)
    return f

將要運(yùn)行的函數(shù)存放在字典中, None 為鍵的列表中存放的是整個(gè)應(yīng)用的所有請求都要運(yùn)行的函數(shù).

from flask import Flask
app = Flask(__name__)

@app.before_first_request
def before_first_request():
  print('before_first_request')


@app.before_request
def before_request():
  print('before_request')


@app.after_request
def after_request(resp):
  print('after_request')
  return resp


@app.teardown_request
def teardown_request(e):
  print('teardown_request')


@app.route("/")
def view_fn():
  return "view_fn"
  
if __name__ == "__main__":
  app.run()

第一次請求：