Django元件的中介軟體
一.中介軟體
1.中介軟體的概念
中介軟體顧名思義,是介於request與response處理之間的一道處理過程,相對比較輕量級,並且在全域性上改變django的輸入與輸出。因為改變的是全域性,所以需要謹慎實用,用不好會影響到效能。
Django預設的Middleware:
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', ]
二.自定義中介軟體
中介軟體中一共有四個方法:
process_request process_view process_exception process_response
1.process_request,process_response
當用戶發起請求的時候會依次經過所有的的中介軟體,這個時候的請求時process_request,最後到達views的函式中,views函式處理後,在依次穿過中介軟體,這個時候是process_response,最後返回給請求者。
上述截圖中的中介軟體都是django中的,我們也可以自己定義一箇中間件,我們可以自己寫一個類,但是必須繼承MiddlewareMixin
需要匯入
1 |
from django.utils.deprecation
import
MiddlewareMixin
|
in views:
def index(request): print("view函式...") return HttpResponse("OK")
in Mymiddlewares.py:
from django.utils.deprecation import MiddlewareMixin from django.shortcuts import HttpResponse class Md1(MiddlewareMixin): def process_request(self,request): print("Md1請求") def process_response(self,request,response): print("Md1返回") return response class Md2(MiddlewareMixin): def process_request(self,request): print("Md2請求")
#return HttpResponse("Md2中斷") def process_response(self,request,response): print("Md2返回") return response
結果:
Md1請求 Md2請求 view函式... Md2返回 Md1返回
注意:如果當請求到達請求2的時候直接不符合條件返回,即return HttpResponse("Md2中斷"),程式將把請求直接發給中介軟體2返回,然後依次返回到請求者,結果如下:
返回Md2中斷的頁面,後臺列印如下:
Md1請求 Md2請求 Md2返回 Md1返回
流程圖如下:
2.process_view
1 |
process_view(
self
, request, callback, callback_args, callback_kwargs)
|
Mymiddlewares.py修改如
from django.utils.deprecation import MiddlewareMixin from django.shortcuts import HttpResponse class Md1(MiddlewareMixin): def process_request(self,request): print("Md1請求") #return HttpResponse("Md1中斷") def process_response(self,request,response): print("Md1返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): print("Md1view") class Md2(MiddlewareMixin): def process_request(self,request): print("Md2請求") return HttpResponse("Md2中斷") def process_response(self,request,response): print("Md2返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): print("Md2view")
結果如下:
Md1請求 Md2請求 Md1view Md2view view函式... Md2返回 Md1返回
下圖進行分析上面的過程:
當最後一箇中間的process_request到達路由關係對映之後,返回到中介軟體1的process_view,然後依次往下,到達views函式,最後通過process_response依次返回到達使用者。
process_view可以用來呼叫檢視函式:
class Md1(MiddlewareMixin): def process_request(self,request): print("Md1請求") #return HttpResponse("Md1中斷") def process_response(self,request,response): print("Md1返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): # return HttpResponse("hello") response=callback(request,*callback_args,**callback_kwargs) return response
結果如下:
Md1請求 Md2請求 view函式... Md2返回 Md1返回
注意:process_view如果有返回值,會越過其他的process_view以及檢視函式,但是所有的process_response都還會執行。
3.process_exception
1 |
process_exception(
self
, request, exception)
|
示例修改如下:
class Md1(MiddlewareMixin): def process_request(self,request): print("Md1請求") #return HttpResponse("Md1中斷") def process_response(self,request,response): print("Md1返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): # return HttpResponse("hello") # response=callback(request,*callback_args,**callback_kwargs) # return response print("md1 process_view...") def process_exception(self): print("md1 process_exception...") class Md2(MiddlewareMixin): def process_request(self,request): print("Md2請求") # return HttpResponse("Md2中斷") def process_response(self,request,response): print("Md2返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): print("md2 process_view...") def process_exception(self): print("md1 process_exception...")
結果如下:
Md1請求 Md2請求 md1 process_view... md2 process_view... view函式... Md2返回 Md1返回
流程圖如下:
當views出現錯誤時:
將md2的process_exception修改如下:
def process_exception(self,request,exception): print("md2 process_exception...") return HttpResponse("error")
結果如下:
Md1請求 Md2請求 md1 process_view... md2 process_view... view函式... md2 process_exception... Md2返回 Md1返回