Django的DRF序列化方法

安装rest_framework
 -- pip install djangorestframework
 -- 注册rest_framework
序列化
 -- Python--json
 -- 第一版 用values以及JsonResponse实现序列化
 -- 第二版 用Django的serialize实现的序列化
  -- 缺点  不能序列化外键关系
 -- 第三版用DRF实现序列化
  -- 第一步声明序列化器
  -- 第二步 使用我们的序列化器序列化queryset
   -- 把模型对象放入序列化器进行字段匹配
    匹配上的字段进行序列化 匹配不上丢弃
  -- 序列化好的数据在ser_obj.data中
 
 -- 外键关系的序列化是嵌套的序列化器对象
  注意many=True

2中序列化方法:

　　

from django.shortcuts import renderfrom django.http import HttpResponse,JsonResponsefrom django.views import Viewfrom djangoDome.models import Book,Publisher,Authorfrom django.core import serializers #django序列化

# 用values  方法获取class BookView(View):    def get(self,request):        book_obj=Book.objects.values("id", "title","pub_time", "publisher")        book_list=list(book_obj) [{}]        ret=[]        for book in book_list:            book["publisher"]={                "id": book["publisher"],                "title": Publisher.objects.filter(id=book["publisher"]).first().title,            }            ret.append(book)        return JsonResponse(ret,safe=False,json_dumps_params={"ensure_ascii": False})

# django的序列化class BookView(View):    def get(self,request):        book_obj=Book.objects.all()        data=serializers.serialize('json',book_obj,ensure_ascii=False)        return HttpResponse(data)

用第三种:

#声明序列化器from rest_framework import serializers

class PublisherSerializer(serializers.Serializer):    id = serializers.IntegerField()    title = serializers.CharField(max_length=32)

class AuthorSerializer(serializers.Serializer):    id = serializers.IntegerField()    name = serializers.CharField(max_length=32)

class BookSerializer(serializers.Serializer):    id = serializers.IntegerField()    title = serializers.CharField(max_length=32)    pub_time = serializers.DateField()    category=serializers.CharField(source='get_category_display') #此处为多选时用

    publisher=PublisherSerializer() #多对一    authors=AuthorSerializer(many=True) #多对多用 many=True------------------------

from rest_framework.views import APIView #视图from djangoDome.models import Bookfrom rest_framework.response import Response #相等于django的render等from SerDemo.serializers import BookSerializer

class BookView(APIView):    def get(self,request):        book_obj=Book.objects.all()#获取所有数据

        # 用序列化器进行序列化        ser_obj= BookSerializer(book_obj,many=True)        return  Response(ser_obj.data)

序列化组件  -- 序列化  -- 反序列化 post请求   -- 确定新增的数据结构   -- 序列化器    -- 正序和反序列化字段不统一l    -- required=False 只序列化不走校验    -- read_only=True  只序列化用    -- write_only=True  只反序列化用    -- 重写create方法   -- 验证通过返回ser_obj.validated_data   -- 验证不通过返回ser_obj.errors     -- 反序列化 put/patch 请求   -- 重写update方法   -- ser_obj = BookSerializer(instance=obj, data=request.data, partial=True)   -- 验证通过返回ser_obj.validated_data   -- 验证不通过返回ser_obj.errors       -- 验证   -- 单个字段的验证  权重 222    def validate_字段名称（self, value）:     不通过 raise serializers.ValidationError("错误信息")     通过 return value   -- 多个字段的验证  权重 333    def validate(self, attrs):     attrs 是所有字段组成的字典     不通过 raise serializers.ValidationError("错误信息")     通过 return attrs   -- 自定义的验证  权重 111    def my_validate(value):     不通过 raise serializers.ValidationError("错误信息")     通过 return value    配置     -- 给字段加validators=[my_validate]  -- ModelSerializer   -- class Meta:     model = 表名     fields = "__all__"     # exclude = [xxxx]     depth = 1     # depth 会让所有的外键关系字段变成read_only=True         -- SerializerMethodField()  方法字段    def get_字段名称（self, obj）:     obj  每次序列化的模型对象     return 自定义的数据

Serializers 序列化组件

 

为什么要用序列化组件

当我们做前后端分离的项目~~我们前后端交互一般都选择JSON数据格式，JSON是一个轻量级的数据交互格式。

那么我们给前端数据的时候都要转成json格式，那就需要对我们从数据库拿到的数据进行序列化。

接下来我们看下django序列化和rest_framework序列化的对比~~

Django的序列化方法

class BooksView(View):
    def get(self, request):
        book_list = Book.objects.values("id", "title", "chapter", "pub_time", "publisher")
        book_list = list(book_list)
        # 如果我们需要取外键关联的字段信息 需要循环获取外键 再去数据库查然后拼接成我们想要的
        ret = []
        for book in book_list:
            pub_dict = {}
            pub_obj = Publish.objects.filter(pk=book["publisher"]).first()
            pub_dict["id"] = pub_obj.pk
            pub_dict["title"] = pub_obj.title
            book["publisher"] = pub_dict
            ret.append(book)
        ret = json.dumps(book_list, ensure_ascii=False, cls=MyJson)
        return HttpResponse(ret)

# json.JSONEncoder.default()
# 解决json不能序列化时间字段的问题
class MyJson(json.JSONEncoder):
    def default(self, field):
        if isinstance(field, datetime.datetime):
            return field.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(field, datetime.date):
            return field.strftime('%Y-%m-%d')
        else:
            return json.JSONEncoder.default(self, field)

.values 序列化结果

from django.core import serializers

# 能够得到我们要的效果 结构有点复杂
class BooksView(View):
    def get(self, request):
        book_list = Book.objects.all()
        ret = serializers.serialize("json", book_list)
        return HttpResponse(ret)

django serializers

DRF序列化的方法

首先，我们要用DRF的序列化，就要遵循人家框架的一些标准，

　　-- Django我们CBV继承类是View，现在DRF我们要用APIView

　　-- Django中返回的时候我们用HTTPResponse，JsonResponse，render ，DRF我们用Response

为什么这么用~我们之后会详细讲~~我们继续来看序列化~~

序列化

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField()
    title = serializers.CharField(max_length=32)
    CHOICES = ((1, "Linux"), (2, "Django"), (3, "Python"))
    chapter = serializers.ChoiceField(choices=CHOICES, source="get_chapter_display")
    pub_time = serializers.DateField()

第一步 声明序列化类

from rest_framework.views import APIView
from rest_framework.response import Response

class BookView(APIView):
    def get(self, request):
        book_list = Book.objects.all()
        ret = BookSerializer(book_list, many=True)
        return Response(ret.data)

第二步 序列化对象

外键关系的序列化

# by gaoxin
from rest_framework import serializers
from .models import Book

class PublisherSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)

class UserSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    name = serializers.CharField(max_length=32)
    age = serializers.IntegerField()

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)
    CHOICES = ((1, "Linux"), (2, "Django"), (3, "Python"))
    chapter = serializers.ChoiceField(choices=CHOICES, source="get_chapter_display", read_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    user = UserSerializer(many=True, read_only=True)

外键关系的序列化

反序列化

当前端给我们发post的请求的时候~前端给我们传过来的数据~我们要进行一些校验然后保存到数据库~

这些校验以及保存工作，DRF的Serializer也给我们提供了一些方法了~~

首先~我们要写反序列化用的一些字段~有些字段要跟序列化区分开~~

Serializer提供了.is_valid()  和.save()方法~~

# serializers.py 文件
class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)
    CHOICES = ((1, "Linux"), (2, "Django"), (3, "Python"))
    chapter = serializers.ChoiceField(choices=CHOICES, source="get_chapter_display", read_only=True)
    w_chapter = serializers.IntegerField(write_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    user = UserSerializer(many=True, read_only=True)

    users = serializers.ListField(write_only=True)
    publisher_id = serializers.IntegerField(write_only=True)

    def create(self, validated_data):
        book = Book.objects.create(title=validated_data["title"], chapter=validated_data["w_chapter"], pub_time=validated_data["pub_time"],                                  publisher_id=validated_data["publisher_id"])
        book.user.add(*validated_data["users"])
        return book

反序列化serializer.py

class BookView(APIView):
    def get(self, request):
        book_list = Book.objects.all()
        ret = BookSerializer(book_list, many=True)
        return Response(ret.data)

    def post(self, request):
        # book_obj = request.data
        print(request.data)
        serializer = BookSerializer(data=request.data)
        if serializer.is_valid():
            print(12341253)
            serializer.save()
            return Response(serializer.validated_data)
        else:
            return Response(serializer.errors)

反序列化views.py

当前端给我们发送patch请求的时候，前端传给我们用户要更新的数据，我们要对数据进行部分验证~~

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)
    CHOICES = ((1, "Linux"), (2, "Django"), (3, "Python"))
    chapter = serializers.ChoiceField(choices=CHOICES, source="get_chapter_display", read_only=True)
    w_chapter = serializers.IntegerField(write_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    user = UserSerializer(many=True, read_only=True)

    users = serializers.ListField(write_only=True)
    publisher_id = serializers.IntegerField(write_only=True)

    def create(self, validated_data):
        book = Book.objects.create(title=validated_data["title"], chapter=validated_data["w_chapter"], pub_time=validated_data["pub_time"],
                                   publisher_id=validated_data["publisher_id"])
        book.user.add(*validated_data["users"])
        return book

    def update(self, instance, validated_data):
        instance.title = validated_data.get("title", instance.title)
        instance.chapter = validated_data.get("w_chapter", instance.chapter)
        instance.pub_time = validated_data.get("pub_time", instance.pub_time)
        instance.publisher_id = validated_data.get("publisher_id", instance.publisher_id)
        if validated_data.get("users"):
            instance.user.set(validated_data.get("users"))
        instance.save()
        return instance

PATCH请求serializers.py

class BookView(APIView):
     def patch(self, request):
        print(request.data)
        book_id = request.data["id"]
        book_info = request.data["book_info"]
        book_obj = Book.objects.filter(pk=book_id).first()
        serializer = BookSerializer(book_obj, data=book_info, partial=True)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.validated_data)
        else:
            return Response(serializer.errors)

PATCH请求views.py

验证

如果我们需要对一些字段进行自定义的验证~DRF也给我们提供了钩子方法~~

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)
    # 省略了一些字段 跟上面代码里一样的
    # 。。。。。
     def validate_title(self, value):
        if "python" not in value.lower():
            raise serializers.ValidationError("标题必须含有Python")
        return value

单个字段的验证

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)
    CHOICES = ((1, "Linux"), (2, "Django"), (3, "Python"))
    chapter = serializers.ChoiceField(choices=CHOICES, source="get_chapter_display", read_only=True)
    w_chapter = serializers.IntegerField(write_only=True)
    pub_time = serializers.DateField()
    date_added = serializers.DateField(write_only=True)
    # 新增了一个上架时间字段
    # 省略一些字段。。都是在原基础代码上增加的
    # 。。。。。。

    # 对多个字段进行验证 要求上架日期不能早于出版日期 上架日期要大
    def validate(self, attrs):
        if attrs["pub_time"] > attrs["date_added"]:
            raise serializers.ValidationError("上架日期不能早于出版日期")
        return attrs

多个字段的验证

def my_validate(value):
    if "敏感词汇" in value.lower:
        raise serializers.ValidationError("包含敏感词汇，请重新提交")
    return value

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32, validators=[my_validate])
    # 。。。。。。
    

验证器 validators

ModelSerializer

现在我们已经清楚了Serializer的用法，会发现我们所有的序列化跟我们的模型都紧密相关~

那么，DRF也给我们提供了跟模型紧密相关的序列化器~~ModelSerializer~~

　　-- 它会根据模型自动生成一组字段

　　-- 它简单的默认实现了.update()以及.create()方法

定义一个ModelSerializer序列化器

class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段

定义ModelSerializer

外键关系的序列化

注意：当序列化类MATE中定义了depth时，这个序列化类中引用字段（外键）则自动变为只读

class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        depth = 1
# depth 代表找嵌套关系的第几层

外键关系序列化

自定义字段

我们可以声明一些字段来覆盖默认字段，来进行自定制~

比如我们的选择字段，默认显示的是选择的key，我们要给用户展示的是value。

class BookSerializer(serializers.ModelSerializer):
    chapter = serializers.CharField(source="get_chapter_display", read_only=True)

    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        depth = 1

自定义字段

Meta中其它关键字参数

class BookSerializer(serializers.ModelSerializer):
    chapter = serializers.CharField(source="get_chapter_display", read_only=True)

    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        depth = 1
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}

Meta中参数

post以及patch请求

由于depth会让我们外键变成只读，所以我们再定义一个序列化的类，其实只要去掉depth就可以了~~

class BookSerializer(serializers.ModelSerializer):
    chapter = serializers.CharField(source="get_chapter_display", read_only=True)

    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}

post/patch请求序列化类

SerializerMethodField

外键关联的对象有很多字段我们是用不到的~都传给前端会有数据冗余~就需要我们自己去定制序列化外键对象的哪些字段~~

class BookSerializer(serializers.ModelSerializer):
    chapter = serializers.CharField(source="get_chapter_display", read_only=True)
    user = serializers.SerializerMethodField()
    publisher = serializers.SerializerMethodField()

    def get_user(self, obj):
        # obj是当前序列化的book对象
        users_query_set = obj.user.all()
        return [{"id": user_obj.pk, "name": user_obj.name} for user_obj in users_query_set]

    def get_publisher(self, obj):
        publisher_obj = obj.publisher
        return {"id": publisher_obj.pk, "title": publisher_obj.title}

    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}

SerializerMethodField

用ModelSerializer改进上面Serializer的完整版

class BookSerializer(serializers.ModelSerializer):
    dis_chapter = serializers.SerializerMethodField(read_only=True)
    users = serializers.SerializerMethodField(read_only=True)
    publishers = serializers.SerializerMethodField(read_only=True)

    def get_users(self, obj):
        # obj是当前序列化的book对象
        users_query_set = obj.user.all()
        return [{"id": user_obj.pk, "name": user_obj.name} for user_obj in users_query_set]

    def get_publishers(self, obj):
        publisher_obj = obj.publisher
        return {"id": publisher_obj.pk, "title": publisher_obj.title}

    def get_dis_chapter(self, obj):
        return obj.get_chapter_display()

    class Meta:
        model = Book
        # fields = "__all__"
        # 字段是有序的
        fields = ["id", "title","dis_chapter", "pub_time", "publishers", "users","chapter", "user", "publisher"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        read_only_fields = ["id", "dis_chapter", "users", "publishers"]
        extra_kwargs = {"title": {"validators": [my_validate,]}, "user": {"write_only": True}, "publisher": {"write_only": True},
                        "chapter": {"write_only": True}}