django---APIView源碼分析

django---APIView源碼分析

前言:APIView基於View 看這部份內容必定要懂django—CBV裏的內容

在django—CBV源碼分析中，咱們是分析的from django.views import View下的執行流程
這篇博客咱們就來了解下APIView是如何執行的，跟django.views模塊下的view有何關聯？
咱們依然從urls.py配置入手分析

from django.conf.urls import url
from django.contrib import admin
from app01 import views

urlpatterns = [
    url(r'^publishes/', views.PublishView.as_view()),
]

views.py

from rest_framework.views import  APIView

class PublishView(APIView):

    def get(self,request):
        publish_list=Publish.objects.all()
        ret=serialize("json",publish_list)

        return HttpResponse(ret)

    def post(self,request):
        pass

一、首先咱們仍是來確認urls.py中as_view是誰執行的?
首先咱們去views.PublishView中找,發現找不到,因此咱們接着再去PublishView的父類APIView中去找,找到了因此執行調用APIView.as_view(),內容以下:

class APIView(View):

    # 多餘的代碼暫且刪掉了
    @classmethod
    def as_view(cls, **initkwargs):
        if isinstance(getattr(cls, 'queryset', None), models.query.QuerySet):
            def force_evaluation():
                raise RuntimeError(
                    'Do not evaluate the `.queryset` attribute directly, '
                    'as the result will be cached and reused between requests. '
                    'Use `.all()` or call `.get_queryset()` instead.'
                )
            cls.queryset._fetch_all = force_evaluation
        
        # 1. super調用父類的as_view的執行結果賦值給view這個變量
        view = super(APIView, cls).as_view(**initkwargs)
        view.cls = cls
        view.initkwargs = initkwargs

        # Note: session based authentication is explicitly CSRF validated,
        # all other authentication is CSRF exempt.
        
        # csrf_exempt 不在執行調用csrf_token那個中間件
        # 中間件是針對全局的 
        # 2. 這裏返回的view就是父類View.view
        return csrf_exempt(view)

二、你們是否是覺得這樣就結束了?NO!NO!NO!
若是是as_view是View的as_view,dispatch是View的dispatch,那rest-framework不就成廢鈔了麼?
as_view的執行結果是dispatch的執行結果,那麼dispatch仍是View的dispatch麼?

1. 咱們先看下views.PublishView裏邊有沒有dispatch,發現沒有
2. 咱們在views.PublishView的父類APIView,發現有
3. 因此dispatch是APIView.dispatch非View.dispatch
4. APIView.dispatch 裏邊有一堆組件,這裏不說

中間的這點代碼跟以前的View.dispatch同樣:
仍是作請求分發,在請求以外又作了一堆事情

if request.method.lower() in self.http_method_names:
        handler = getattr(self, request.method.lower(),
                          self.http_method_not_allowed)
    else:
        handler = self.http_method_not_allowed

    response = handler(request, *args, **kwargs)

總結:

url 轉變過程

1. url(r'^publishes/', views.PublishView.as_view()),
2. url(r'^publishes/', APIView.as_view()),
3. url(r'^publishes/', View.as_view()),

View.as_view()咱們在django—CBV講解過了
因此最後調用仍是,只是APIView.as_view在裏邊加了一些他本身定義的一些東西,只是咱們沒用到而已

APIView.as_view()---> View.as_view()---> APIView.dispatch()--->response--->handler()--> 本身定義請求方法函數的返回結果,不然就拋錯405