Rest_Framework由淺入深：從CBV到ModelViewSet源碼一步步解析

1、Django Rest_Framework介紹

Django REST framework是一個建立在Django基礎(chǔ)之上的Web應(yīng)用開發(fā)框架，可以快速的開發(fā)REST API接口應(yīng)用。在REST framework中，提供了序列化器Serialzier的定義，可以幫助我們簡化序列化與反序列化的過程，不僅如此，還提供豐富的類視圖、擴展類、視圖集來簡化視圖的編寫工作。REST framework還提供了認證、權(quán)限、限流、過濾、分頁、接口文檔等功能支持。REST framework提供了一個API 的Web可視化界面來方便查看測試接口。

2、特點

a、提供了定義序列化器Serializer的方法，可以快速根據(jù) Django ORM或者其它庫自動序列化、反序列化；
b、提供了豐富的類視圖、Mixin擴展類，簡化視圖的編寫，豐富的定制層級：函數(shù)視圖、類視圖、視圖集合到自動生成 API；
c、滿足各種需要多種身份認證和權(quán)限認證方式的支持內(nèi)置了限流系統(tǒng)直觀的 API web 界面，可以方便我們調(diào)試開發(fā)api接口，可擴展性強，插件豐富。

一、Django的CBV

1、執(zhí)行順序：

先從路由的as_view() 開始，
執(zhí)行BookView類繼承的View類里的as_view() 里的view(),
view() 的返回值是View類的dispatch()，
dispatch() 進行分發(fā)執(zhí)行get、post、put等方法。

views.py

# author xsy

from django.views import View

class BookView(View):

    def get(self,request):
        return HttpResponse('get')
    def post(self,request):
        return HttpResponse('post')

urls.py

# author xsy

from django.urls import path
from .views import *
urlpatterns = [
    path('book/', BookView.as_view()),
]

View類的大概邏輯

# author xsy

class View():

    def as_view(cls, **initkwargs):
        def view(self):
            return self.dispatch()
        return view
    
    def dispatch(self, request, *args, **kwargs):
        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
        return handler(request, *args, **kwargs)

二、DRF的APIView

1、相比原生django的優(yōu)勢：

a、django原生的request.POST存在只會解析uriencoded 不會解析json的問題；
b、APIView類的dispatch方法解決該問題，而且還會對請求的客戶端進行身份認證、權(quán)限檢查、流量控制。

2、執(zhí)行順序：

先從路由的as_view() 開始，
執(zhí)行BookView類繼承的APIView類里的as_view()，
而該as_view() 在內(nèi)部重寫了APIView類的父類View的as_view() 方法，
所以執(zhí)行的是父類View的as_view()，
而View的as_view()方法在內(nèi)部的返回值是dispatch()
該dispatch()是先從APIView類里查找，
因為APIView類有dispatch()，
所以最終執(zhí)行的是APIView類的dispatch() 進行分發(fā)。

views.py

# author xsy

from rest_framework.views import APIView

class BookView(APIView):

    def get(self,request):
        return HttpResponse('get')
    def post(self,request):
        return HttpResponse('post')

APIView類的大概邏輯

# author xsy

# APIView的父類View的邏輯
class View():

    def as_view(cls, **initkwargs):
        def view(self):
            return self.dispatch()
        return view
    
    def dispatch(self, request, *args, **kwargs):
        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
        return handler(request, *args, **kwargs)
        
class APIView(View):
    def as_view(cls, **initkwargs):
        view = super().as_view(**initkwargs)
        return csrf_exempt(view)

    def dispatch(self, request, *args, **kwargs):
        # 構(gòu)建新的request對象
        request = self.initialize_request(request, *args, **kwargs)
        self.request = request
        # 初始化：認證、權(quán)限、限流組件三件套

        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
        return handler(request, *args, **kwargs)

三、序列化器

1、使用Serializer和APIView

Serializer進行序列化和反序列化
數(shù)據(jù)庫的數(shù)據(jù)到前端進行序列化
前端的數(shù)據(jù)上傳到數(shù)據(jù)庫進行反序列化

a、**serializer.save()**的邏輯:

如果self.instance is not None執(zhí)行update()
否則執(zhí)行create() 分別對應(yīng)put()和post()
但BaseSerializer類里的create()和update()必須重寫
所以Bookserializers類里有這兩個方法

b、serializer.data

BookView類get()返回的serializer.data，是Serializer類data()
該方法重寫了Serializer類的父類BaseSerializer類的data()方法
model.py

# author xsy

from django.db import models

# Create your models here.

class Books(models.Model):
    title = models.CharField(max_length=32,verbose_name="書籍名稱")
    price = models.IntegerField(verbose_name="價格")

serializers.py

# author xsy

from rest_framework import serializers
from .models import *
class Bookserializers(serializers.Serializer):
    title = serializers.CharField(max_length=16)
    price = serializers.IntegerField()
    # 使用下面這種可以修改名稱
    # jiaqian = serializers.IntegerField(source='price')

    def create(self, validated_data):
        newbook = Books.objects.create(**self.validated_data)
        return newbook
    def update(self, instance, validated_data):
        Books.objects.filter(pk=instance.pk).update(**self.validated_data)
        update_book = Books.objects.get(pk=instance.pk)
        return update_book

views.py

# author xsy

from rest_framework.views import APIView
# 不使用djangO自帶的HttpResponse  而是用rest_framework的Response可以將返回值變成json
from rest_framework.response import Response
from .models import *
from .serializers import *

class BookView(APIView):
    def get(self,request):
        books = Books.objects.all()
        serializer = Bookserializers(instance=books,many=True)
        return Response(serializer.data)
    def post(self,request):
        serializer = Bookserializers(data=request.data)
        if serializer.is_valid():
            # Books.objects.create(**serializer.validated_data)
            serializer.save()
            return Response(serializer.data)
        else:
            return Response(serializer.errors)

class BookDetailView(APIView):
    def get(self,request,id):
        book = Books.objects.get(pk=id)
        serializer = Bookserializers(instance=book,many=False)
        return Response(serializer.data)
    def put(self,request,id):
        serializer = Bookserializers(instance=Books.objects.get(pk=id),data=request.data)
        if serializer.is_valid():
            # Books.objects.filter(pk=id).update(**serializer.validated_data)
            # serializer.instance = Books.objects.get(pk=id)
            serializer.save()
            return Response(serializer.data)
        else:
            return Response(serializer.errors)
    def delete(self,request,id):
        Books.objects.get(pk=id).delete()
        return Response()

urls.py

# author xsy

from django.urls import path,re_path
from .views import *
urlpatterns = [
    path('books/', BookView.as_view()),
    re_path('book/(\d+)', BookDetailView.as_view()),
]

2、ModelSerializer和GenericAPIView

a、ModelSerializer相比Serializer

已經(jīng)將模型的字段在內(nèi)部進行封裝；
在內(nèi)部已經(jīng)重寫create()和update()；

b、GenericAPIView相當于進一步封裝APIView

1、GenericAPIView繼承APIView類，self.get_serializer_class()等于Bookserializers
2、而self.get_serializer等于self.get_serializer_class()
3、self.get_queryset() 等于取出多條數(shù)據(jù)
4、self.get_object() 等于取出一條數(shù)據(jù)
model.py

# author xsy

from django.db import models

# Create your models here.

class Books(models.Model):
    title = models.CharField(max_length=32,verbose_name="書籍名稱")
    price = models.IntegerField(verbose_name="價格")

serializers.py

# author xsy

class Bookserializers(serializers.ModelSerializer):

    class Meta:
        model = Books
        # fields = '__all__'
        fields = ['title','price']

views.py

# author xsy

from rest_framework.generics import GenericAPIView
from rest_framework.response import Response

class BookView(GenericAPIView):
    queryset = Books.objects.all()
    serializer_class = Bookserializers
    def get(self, request):
        books = Books.objects.all()
        # serializer = Bookserializers(instance=self.get_queryset(),many=True)
        # self.get_serializer_class()等于Bookserializers
        # self.get_serializer_class()(instance=self.get_queryset(),many=True)
        serializer = self.get_serializer(instance=self.get_queryset(),many=True)
        return Response(serializer.data)
    def post(self,request):
        # serializer = Bookserializers(data=request.data)
        # serializer = self.get_serializer_class()(data=request.data)
        # 三行作用相同
        serializer = self.get_serializer(data=request.data)
        if serializer.is_valid():
            # Books.objects.create(**serializer.validated_data)
            serializer.save()
            return Response(serializer.data)
        else:
            return Response(serializer.errors)

class BookDetailView(GenericAPIView):
    queryset = Books.objects.all()
    serializer_class = Bookserializers
    def get(self,request,pk):
        # book = Books.objects.get(pk=id)
        # serializer = Bookserializers(instance=book,many=False)
        serializer = self.get_serializer(instance=self.get_object(),many=False)
        return Response(serializer.data)
    def put(self,request,pk):
        # serializer = Bookserializers(instance=Books.objects.get(pk=id),data=request.data)
        serializer = self.get_serializer(instance=self.get_object(),data=request.data)
        if serializer.is_valid():
            # Books.objects.filter(pk=id).update(**serializer.validated_data)
            # serializer.instance = Books.objects.get(pk=id)
            serializer.save()
            return Response(serializer.data)
        else:
            return Response(serializer.errors)
    def delete(self,request,pk):
        # Books.objects.get(pk=id).delete()
        self.get_object().delete()
        return Response()

四、視圖

1、mixins

ListModelMixin的list方法對應(yīng)BookView的get方法
CreateModelMixin的create方法對應(yīng)BookView的post方法
RetrieveModelMixin的retrieve方法對應(yīng)BookDetailView的get方法
UpdateModelMixin的update方法對應(yīng)BookDetailView的put方法
DestroyModelMixin的destroy方法對應(yīng)BookDetailView的delete方法
views.py

# author xsy

# #  #################### mixins  ################################

from rest_framework.mixins import ListModelMixin,CreateModelMixin,UpdateModelMixin,RetrieveModelMixin,DestroyModelMixin

class BookView(ListModelMixin,CreateModelMixin,GenericAPIView):
    queryset = Books.objects.all()
    serializer_class = Bookserializers

    def get(self,request):
        return self.list(request)
    def post(self,request):
        return self.create(request)

class BookDetailView(RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin,GenericAPIView):
    queryset = Books.objects.all()
    serializer_class = Bookserializers

    def get(self,request,pk):
        return self.retrieve(request,pk)
    def put(self,request,pk):
        return self.update(request,pk)
    def delete(self,request,pk):
        return self.destroy(request,pk)

2、mixins再封裝版

ListCreateAPIView類將list方法封裝到get方法里，將create方法封裝到post方法里
RetrieveUpdateDestroyAPIView類將retrieve封裝到get方法里，將update方法封裝到put方法里，將destroy方法封裝到delete方法里
views.py

# author xsy

# #  #################### mixins再封裝  #########################################

from rest_framework.generics import ListCreateAPIView,RetrieveUpdateDestroyAPIView
class BookView(ListCreateAPIView):
    queryset = Books.objects.all()
    serializer_class = Bookserializers

class BookDetailView(RetrieveUpdateDestroyAPIView):
    queryset = Books.objects.all()
    serializer_class = Bookserializers

五、視圖的再次精簡化：GenericViewSet和ModelViewSet

1、GenericViewSet

BookView類繼承六個類，其中GenericViewSet類繼承的ViewSetMixin類實現(xiàn)了將路由傳的字典映射到對應(yīng)的方法，這樣才可以將BookView和BookDetailView和成一個類，而繼承的其他五個類對應(yīng)了增刪改查方法
views.py

# author xsy

#  #################### 四、GenericViewSet  #########################################

from rest_framework.viewsets import GenericViewSet
from rest_framework.mixins import ListModelMixin,CreateModelMixin,UpdateModelMixin,RetrieveModelMixin,DestroyModelMixin

class BookView(GenericViewSet,ListModelMixin,CreateModelMixin,UpdateModelMixin,RetrieveModelMixin,DestroyModelMixin):
    queryset = Books.objects.all()
    serializer_class = Bookserializers

urls.py

# author xsy

urlpatterns = [
    # GenericViewSet
    path('books/', BookView.as_view({'get':'list','post':'create'})),
    re_path('book/(?P<pk>\d+)', BookView.as_view({'get':'retrieve','delete':'destroy','put':'update'})),
    ]

2、ModelViewSet

ModelViewSet類繼承了CreateModelMixin, RetrieveModelMixin, UpdateModelMixin, DestroyModelMixin,ListModelMixin,
GenericViewSet這六個類
views.py

# author xsy

from rest_framework.viewsets import ModelViewSet

class BookView(ModelViewSet):
    queryset = Books.objects.all()
    serializer_class = Bookserializers

urls.py文章來源地址http://www.zghlxwxcb.cn/news/detail-464343.html

# author xsy

from rest_framework import routers

router = routers.DefaultRouter()
router.register('book',BookView)
urlpatterns = [

]
urlpatterns += router.urls

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