Django Rest Framework -Serializers 序列化组件

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

# 第二版 django的序列化
class BookView(View):
    def get(self, request):
        book_queryset = Book.objects.all()
        data = serializers.serialize("json", book_queryset, ensure_ascii=False)
        return HttpResponse(data)

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

　　
　　-- 安装  rest_framework      pip install djangorestframework
　　-- 注册  rest_framework

序列化

from rest_framework import serializers


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


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


class BookSerializers(serializers.Serializer):
    id = serializers.IntegerField()
    title = serializers.CharField(max_length=32)
    pub_time = serializers.DateField()
    category = serializers.CharField(source='get_category_display')  # source叫资源,后面接的都是ORM操作
    publisher = PublisherSerializers()
    author = AuthorSerializers(many=True)  # 多对多

from django.shortcuts import render
from app01 import models
from rest_framework.views import APIView
from .serializers import BookSerializers
from rest_framework.response import Response


class BookView(APIView):
    def get(self, request):
        book_queryset = models.Book.objects.all()
        # 用序列化器进行序列化
        ser_obj = BookSerializers(book_queryset, many=True)  # many=True可以放多个
        return Response(ser_obj.data)

外键关系的序列化

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~~

class BookSerializers(serializers.Serializer):
    id = serializers.IntegerField(required=False)  # required=False反序时候不进行校验
    title = serializers.CharField(max_length=32)
    pub_time = serializers.DateField()
    category = serializers.CharField(source='get_category_display', read_only=True)  # source叫资源,后面接的都是ORM操作
    post_category = serializers.IntegerField(write_only=True)  # write_only=True 只反序时候用
    publisher = PublisherSerializers(read_only=True)  # read_only=True 这个加上只正序的时候用,反序时候不用
    publisher_id = serializers.IntegerField(write_only=True)
    author = AuthorSerializers(many=True, read_only=True)  # 多对多
    author_list = serializers.ListField(write_only=True)

    def create(self, validated_data):
        print(validated_data)
        book_obj = models.Book.objects.create(title=validated_data['title'], pub_time=validated_data['pub_time'],
                                              category=validated_data['post_category'],
                                              publisher_id=validated_data['publisher_id'])
        book_obj.author.add(*validated_data['author_list'])
        return book_obj

from django.shortcuts import render
from app01 import models
from rest_framework.views import APIView
from .serializers import BookSerializers
from rest_framework.response import Response


class BookView(APIView):
    def get(self, request):
        book_queryset = models.Book.objects.all()
        # 用序列化器进行序列化
        ser_obj = BookSerializers(book_queryset, many=True)  # many=True可以放多个
        return Response(ser_obj.data)

    def post(self, request):
        book_obj = request.data
        ser_obj = BookSerializers(data=book_obj)
        if ser_obj.is_valid():
            ser_obj.save()
            return Response(ser_obj.validated_data)
        return Response(ser_obj.errors)


class BookEditView(APIView):
    def get(self, request, id):
        book_obj = models.Book.objects.filter(id=id)
        ser_obj = BookSerializers(book_obj)
        return Response(ser_obj.data)

        -- 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
                -- 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

当前端给我们发送put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 BookSerializers(serializers.Serializer):
    id = serializers.IntegerField(required=False)  # required=False反序时候不进行校验
    title = serializers.CharField(max_length=32)
    pub_time = serializers.DateField()
    category = serializers.CharField(source='get_category_display', read_only=True)  # source叫资源,后面接的都是ORM操作
    post_category = serializers.IntegerField(write_only=True)  # write_only=True 只反序时候用
    publisher = PublisherSerializers(read_only=True)  # read_only=True 这个加上只正序的时候用,反序时候不用
    publisher_id = serializers.IntegerField(write_only=True)
    author = AuthorSerializers(many=True, read_only=True)  # 多对多
    author_list = serializers.ListField(write_only=True)

    def create(self, validated_data):
  
        book_obj = models.Book.objects.create(title=validated_data['title'], pub_time=validated_data['pub_time'],
                                              category=validated_data['post_category'],
                                              publisher_id=validated_data['publisher_id'])
        book_obj.author.add(*validated_data['author_list'])
        return book_obj

    def update(self, instance, validated_data):
        # instance 更新的book_obj 对象
        #         # validated_data 校验通过的数据
        #         # ORM做更新操作
        instance.title = validated_data.get('title', instance.title)
        instance.pub_time = validated_data.get('pub_time', instance.pub_time)
        instance.category = validated_data.get('post_category', instance.category)
        instance.publisher_id = validated_data.get('publisher_id', instance.publisher_id)
        if validated_data.get('author_list'):
            instance.author.set(validated_data['author_list'])
        instance.save()
        return instance

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

    def put(self, request, id):
        book_obj = models.Book.objects.filter(id=id).first()
        ser_obj = BookSerializers(instance=book_obj, data=request.data, partial=True)  # partial=True部分校验
        if ser_obj.is_valid():
            ser_obj.save()
            return Response(ser_obj.validated_data)
        return Response(ser_obj.errors)

 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)

     def validate_title(self, value):
        if "python" not in value.lower():
            raise serializers.ValidationError("标题必须含有Python")
        return value

   def validate(self, attrs):
#         print(33333)
#         # attrs 字典有你传过来的所有的字段
#         print(attrs)
#         if "python" in attrs["title"].lower() or attrs["post_category"] == 1:
#             return attrs
#         else:
#             raise serializers.ValidationError("分类或标题不合符要求")

def my_validate(value):
    if "敏感" 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]) # validators=[my_validate]自定义校验

 

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

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 #depth基本不用,外键关系向下找1层,会让你这些所有的外键关系变成read_only = True
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}

Meta中参数

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

ModelSerializer完整版

class BookSerializers(serializers.ModelSerializer):
    # 重写正序字段
    publisher_info = serializers.SerializerMethodField()  # 方法字段
    author_info = serializers.SerializerMethodField()
    category_info = serializers.SerializerMethodField()

    def get_publisher_info(self, obj):  # get+字段名就是一个钩子函数
        # obj 就是视图传过来的 序列化的每个Book对象
        publisher_obj = obj.publisher
        return {"id": publisher_obj.id, 'title': publisher_obj.title}

    def get_author_info(self, obj):
        author_obj = obj.author.all()  # 多对多
        return [{"id": author.id, "name": author.name} for author in author_obj]

    def get_category_info(self, obj):
        return obj.get_category_display()  # 多选字段调用display()方法进行返回

    class Meta:
        # 反序用默认的
        model = models.Book
        fields = "__all__"
        # depth = 1  # depth 基本不用,外键关系向下找1层,会让你这些所有的外键关系变成read_only = True
        extra_kwargs = {"publisher": {"write_only": True}, "author": {"write_only": True},"category":{"write_only": True}}