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  • django rest_framework 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
    复制代码
    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.data)
            else:
                return Response(serializer.errors)
    复制代码

     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~~

    复制代码
    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,]}}
    复制代码

    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}}
    ModelSerializer
     
     
     
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  • 原文地址:https://www.cnblogs.com/niuli1987/p/10257580.html
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