詳解Django中間件的5種自定義方法

更新時間：2018年07月26日 09:21:19 作者：不_一

這篇文章主要介紹了詳解Django中間件的5種自定義方法,小編覺得挺不錯的，現(xiàn)在分享給大家，也給大家做個參考。一起跟隨小編過來看看吧

Django中間件

在http請求到達視圖函數(shù)之前和視圖函數(shù)return之后，django會根據(jù)自己的規(guī)則在合適的時機執(zhí)行中間件中相應(yīng)的方法。

中間件的執(zhí)行流程

1、執(zhí)行完所有的request方法到達視圖函數(shù)。

2、執(zhí)行中間件的其他方法

3、經(jīng)過所有response方法返回客戶端。

注意：如果在其中1個中間件里 request方法里 return了值，就會執(zhí)行當(dāng)前中間件的response方法，返回給用戶然后報錯。。不會再執(zhí)行下一個中間件。

自定義中間件

1.在project下隨便創(chuàng)建一個py文件

from django.utils.deprecation import MiddlewareMixin
class Middle1(MiddlewareMixin):
 def process_request(self,request):
  print("來了")
 def process_response(self, request,response):
  print('走了')

2、在setings文件中注冊這個 py文件

django項目的settings模塊中，有一個 MIDDLEWARE_CLASSES變量，其中每一個元素就是一個中間件

MIDDLEWARE = [
 'django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'M1.Middle1',
]

執(zhí)行結(jié)果

為啥報錯了呢?

因為自定義的中間件response方法沒有return，交給下一個中間件，導(dǎo)致http請求中斷了?。?！

注意自定義的中間件request 方法不要return 因為返回值中間件不再往下執(zhí)行，導(dǎo)致 http請求到達不了視圖層，因為request在視圖之前執(zhí)行！

from django.utils.deprecation import MiddlewareMixin
class Middle1(MiddlewareMixin):
 def process_request(self,request):
  print("來了") #不用return Django內(nèi)部自動幫我們傳遞
 def process_response(self, request,response):
  print('走了')
  return response #執(zhí)行完了這個中間件一定要 傳遞給下一個中間件

中間件（類）中5種方法

中間件中可以定義5個方法，分別是：

process_request(self,request)
process_view(self, request, callback, callback_args, callback_kwargs)
process_template_response(self,request,response)
process_exception(self, request, exception)
process_response(self, request, response

1、 process_view（self, request, callback, callback_args, callback_kwargs）方法介紹

(1)執(zhí)行完所有中間件的request方法‘

(2)url匹配成功

(3)拿到視圖函數(shù)的名稱、參數(shù)，（注意不執(zhí)行）再執(zhí)行process_view()方法

(4)最后去執(zhí)行視圖函數(shù)

玩法1（常規(guī)）

from django.utils.deprecation import MiddlewareMixin


class M1(MiddlewareMixin):
 def process_request(self, request):
  print('M1.request') 

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M1.process_view")
  
 def process_response(self, request, response):
  print('M1.response')
  return response 



class M2(MiddlewareMixin):
 def process_request(self, request):
  print('M2.request') 

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M2.process_view")
 
 def process_response(self, request, response):
  print('M2.response')
  return response

執(zhí)行結(jié)果

玩法2

既然 process_view 拿到視圖函數(shù)的名稱、參數(shù)，（不執(zhí)行）再執(zhí)行process_view()方法，最后才去執(zhí)行視圖函數(shù)！

那可以在執(zhí)行process_view環(huán)節(jié)直接把函數(shù)執(zhí)行返回嗎？

from django.utils.deprecation import MiddlewareMixin
class M1(MiddlewareMixin):
 def process_request(self, request):
  print('M1.request')
     # callback視圖函數(shù)名稱 callback_args,callback_kwargs 視圖函數(shù)執(zhí)行所需的參數(shù)
 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M1.process_view")
  response=callback(request,*callback_args,**callback_kwargs)
  return response
 def process_response(self, request, response):
  print('M1.response')
  return response

class M2(MiddlewareMixin):
 def process_request(self, request):
  print('M2.request') 

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M2.process_view")
 def process_response(self, request, response):
  print('M2.response')
  return response

執(zhí)行結(jié)果

結(jié)論：

如果process_view函數(shù)有返回值，跳轉(zhuǎn)到最后一個中間件，執(zhí)行最后一個中間件的response方法，逐步返回。

和 process_request方法不一樣哦！ request方法在當(dāng)前中間件的response方法返回。

2、process_exception(self, request, exception)方法

from django.utils.deprecation import MiddlewareMixin


class M1(MiddlewareMixin):
 def process_request(self, request):
  print('M1.request')
  
 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M1.process_view")

 def process_response(self, request, response):
  print('M1.response')
  return response

 def process_exception(self, request,exception):
  print('M1的process_exception')


class M2(MiddlewareMixin):
 def process_request(self, request):
  print('M2.request') 

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M2.process_view")

 def process_response(self, request, response):
  print('M2.response')
  return response

 def process_exception(self, request, exception):
  print('M2的process_exception')

我去加了process_exception方法咋啥也沒執(zhí)行呢？?。≡瓉硎莗rocess_exception默認不執(zhí)行?。?！

大爺?shù)?原來process_exception方法在視圖函數(shù)執(zhí)行出錯的時候才會執(zhí)行

M1.request
M2.request
M1.process_view
M2.process_view
執(zhí)行index
M2的process_exception
M1的process_exception
Internal Server Error: /index/
Traceback (most recent call last):
 File "C:\Users\Administrator\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\handlers\exception.py", line 41, in inner
 response = get_response(request)
 File "C:\Users\Administrator\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\handlers\base.py", line 187, in _get_response
 response = self.process_exception_by_middleware(e, request)
 File "C:\Users\Administrator\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\handlers\base.py", line 185, in _get_response
 response = wrapped_callback(request, *callback_args, **callback_kwargs)
 File "F:\untitled1\app01\views.py", line 7, in index
 int("ok")
ValueError: invalid literal for int() with base 10: 'ok'
M2.response
M1.response
[03/Jul/2017 16:43:59] "GET /index/ HTTP/1.1" 500 62663

1、執(zhí)行完所有 request 方法

2、執(zhí)行所有 process_view方法

3、如果視圖函數(shù)出錯，執(zhí)行process_exception（最終response，process_exception的return值）

如果process_exception 方法有了返回值就不再執(zhí)行其他中間件的 process_exception，直接執(zhí)行response方法響應(yīng)

4.執(zhí)行所有response方法

5.最后返回process_exception的返回值

M1.request
M2.request
M1.process_view
M2.process_view
執(zhí)行index
M2的process_exception （有了return值，直接執(zhí)行response）
M2.response
M1.response

process_exception的應(yīng)用

在視圖函數(shù)執(zhí)行出錯時，返回錯誤信息。這樣頁面就不會報錯了！

class M1(MiddlewareMixin):
 def process_request(self, request):
  print('M1.request')

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M1.process_view")

 def process_response(self, request, response):
  print('M1.response')
  return response

 def process_exception(self, request,exception):
  print('M1的process_exception')


class M2(MiddlewareMixin):
 def process_request(self, request):
  print('M2.request')

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M2.process_view")

 def process_response(self, request, response):
  print('M2.response')
  return response

 def process_exception(self, request, exception):
  print('M2的process_exception')
  return HttpResponse('出錯了兄弟?。?！')

3、process_template_response()

from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse

class M1(MiddlewareMixin):
 def process_request(self, request):
  print('M1.request')

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M1.process_view")

 def process_response(self, request, response):
  print('M1.response')
  return response


 def process_exception(self, request,exception):
  print('M1的process_exception')


class M2(MiddlewareMixin):
 def process_request(self, request):
  print('M2.request')

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M2.process_view")

 def process_response(self, request, response):
  print('M2.response')
  return response

 def process_exception(self, request, exception):
  print('M2的process_exception')

 def process_template_response(self,request,response):
  print('M2process_template_response')
  return response

process_template_response()默認不執(zhí)行

rocess_template_response()特性

只有在視圖函數(shù)的返回對象中有render方法才會執(zhí)行！

并把對象的render方法的返回值返回給用戶（注意不返回視圖函數(shù)的return的結(jié)果了，而是返回視圖函數(shù) return值（對象）的render方法）

from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse


class M1(MiddlewareMixin):
 def process_request(self, request):
  print('M1.request')

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M1.process_view")

 def process_response(self, request, response):
  print('M1.response')
  return response


 def process_exception(self, request,exception):
  print('M1的process_exception')


class M2(MiddlewareMixin):
 def process_request(self, request):
  print('M2.request')

 def process_view(self, request,callback,callback_args,callback_kwargs ):
  print("M2.process_view")

 def process_response(self, request, response):
  print('M2.response')
  return response

 def process_exception(self, request, exception):
  print('M2的process_exception')

 def process_template_response(self,request,response): #如果視圖函數(shù)中的返回值 中有render方法，才會執(zhí)行 process_template_response
  print('M2process_template_response')
  return response

視圖函數(shù)

from django.shortcuts import render,HttpResponse

# Create your views here.
class Foo():
 def __init__(self,requ):
  self.req=requ
 def render(self):
  return HttpResponse('OKKKK')

def index(request):
 print("執(zhí)行index")
 obj=Foo(request)
 return obj

執(zhí)行結(jié)果

應(yīng)用：

既然process_template_respnse,不返回視圖函數(shù)的return的結(jié)果，而是返回視圖函數(shù) return值（對象）的render方法;(多加了一個環(huán)節(jié))

就可以在這個視圖函數(shù)返回對象的 render方法里，做返回值的二次加工了！多加工幾個，視圖函數(shù)就可以隨便使用了！

（好比噴霧器有了多個噴頭，換不同的噴頭噴出不同水，返回值就可以也組件化了）

from django.shortcuts import render,HttpResponse

# Create your views here.
class Dict(): #對視圖函數(shù)返回值做二次封裝 ??！
 def __init__(self,requ,msg):
  self.req=requ 
  self.msg=msg
 def render(self):
  a=self.msg #在render方法里面 把視圖函數(shù)的 返回值 制作成字典 、列表等。。。 
     # 如果新增了其他 一個視圖函數(shù)直接，return對象 即可！不用每個視圖函數(shù)都寫 制作字典 列表 拼接的邏輯了
  return HttpResponse(a) #

def index(request):
 print("執(zhí)行index")
 obj=Dict(request,"vv")
 return obj