一：几种序列化方式与rest_framework视图的初级使用

1、json模块: 不支持序列化queryset和object对象

from django.shortcuts import render, HttpResponse
from app01 import models
from django import views
import json
class BookView(views.View):
    # json 不支持序列化queryset和object对象
    def get(self, request):
        book_list = models.Book.objects.all().values('pk', 'title', 'price')
        book_list_json = json.dumps(list(book_list))
        return HttpResponse(book_list_json)

        # from django.forms.models import model_to_dict
        # import json
        # data=[]
        # for obj in book_list:
        #     data.append(model_to_dict(obj))
        # print(data)
        # return HttpResponse(json.dumps(data))

2、django内置serializers：支持将queryset对象转换成json格式

from django.shortcuts import render, HttpResponse
from django.core import serializers
from app01 import models
from django import views

class BookView(views.View):
        # django自带的序列化组件serializers
        def get(self, request):
            book_list = models.Book.objects.all()
            book_list_json = serializers.serialize('json', book_list)  # ('格式', queryset)
            return HttpResponse(book_list_json)

3、rest_framework的serializers：支持将queryset对象转换成json格式，且支持object对象。更方便的更新数据库

from django.shortcuts import render, HttpResponse
from rest_framework import serializers
from app01 import models
from django import views

class BookSerializers(serializers.ModelSerializer):
    # authors = AuthorsSerializers(many=True)
　　
    class Meta:
        model = models.Book
        # fields = ["title", "price", "publish_id", "pub_date", "authors"]
        fields = "__all__"
        extra_kwargs = {
            'title': {"error_messages": {"required": "书名内容不能为空"}},
            'publish': {"error_messages": {"required": '出版社不能为空'}},
            'price': {"error_messages": {"required": '价格不能为空'}}
        }
        depth = 1  # 获取表中的多对多字段深度

class BookView(APIView):
    def get(self, request):
        Book_list = models.Book.objects.all()
        ser = BookSerializers(Book_list, many=True)  # queryset对象many=True，object对象默认为False
        ser = ser.data  # data取出序列化后的数据
        # print(ser, type(ser))
        # return Response(ser)  # 继承REST framework下的APIview才能使用，响应器自动处理OrderedDict

        return HttpResponse(ser)  #OrderedDict

　　　　提交post请求：将post数据交给序列化类，判断后save即可（django原生View下的post只能取form-data数据，rest_framework的APIView下，用request.data取post数据，且能取到其它原生格式，json等）。如果序列化类设置depth深度后，post请求时，数据容易更新失败。

def post(self, request):
    ser = BookSerializers(data=request.data)
    if ser.is_valid():
        ser.save()
        return HttpResponse(json.dumps(ser.data))
     else:
        print(ser.errors)
        return HttpResponse(json.dumps(ser.errors))

　　　　重写save中的create和update方法：save方法实际是判断数据是否已经存在后，默认调用ModelSerializer类下的create或者update方法，我们可以在自己的序列化类中覆盖它们

class BookSerializers(serializers.ModelSerializer):

      class Meta:
          model=Book
          fields="__all__"
          # exclude = ['authors',]
          # depth=1

      def create(self, validated_data):
        
          authors = validated_data.pop('authors')
          obj = Book.objects.create(**validated_data)
          obj.authors.add(*authors)
          return obj

　　　　单条数据的get、put和delete请求：

class BookDetailView(APIView):
    def get(self, request, id):
        book_obj = models.Book.objects.filter(pk=id).first()
        ser = BookSerializers(book_obj)
        data = ser.data
        return Response(data)

    def put(self, request, id):
        book_obj = models.Book.objects.filter(pk=id).first()
        ser = BookSerializers(book_obj, data=request.data)
        if ser.is_valid():
            ser.save()
            return Response(ser.data)
        else:
            return Response(ser.errors)

    def delete(self, request, id):
        models.Book.objects.filter(pk=id).delete()
        return Response('删除成功')