drf3 Serializers 序列化组件

为什么要用序列化组件

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。
给前端数据的时候都要转成json格式，那就需要对从数据库拿到的数据进行序列化。
django序列化和rest_framework序列化的对比
将后端数据库中的信息用json的格式传给前端

数据准备

DRFDemo/urls.py

from django.contrib import admin
from django.urls import path, include


urlpatterns = [
    path('admin/', admin.site.urls),
    path('books/', include("SerDemo.urls")),

]





SerDemo/urls.py

urlpatterns = [
    path('list', BookView.as_view()),
    path('retrieve/<int:id>', BookEditView.as_view()),

]

from django.db import models

# Create your models here.

__all__ = ["Book", "Publisher", "Author"]


class Book(models.Model):
    title = models.CharField(max_length=32, verbose_name="图书名称")
    CHOICES = ((1, "Python"), (2, "Go"), (3, "Linux"))
    category = models.IntegerField(choices=CHOICES, verbose_name="图书的类别")
    pub_time = models.DateField(verbose_name="图书的出版日期")

    publisher = models.ForeignKey(to="Publisher", on_delete=None)
    author = models.ManyToManyField(to="Author")

    def __str__(self):
        return self.title

    class Meta:
        verbose_name_plural = "01-图书表"
        db_table = verbose_name_plural


class Publisher(models.Model):
    title = models.CharField(max_length=32, verbose_name="出版社的名称")

    def __str__(self):
        return self.title

    class Meta:
        verbose_name_plural = "02-出版社表"
        db_table = verbose_name_plural


class Author(models.Model):
    name = models.CharField(max_length=32, verbose_name="作者的姓名")

    def __str__(self):
        return self.name

    class Meta:
        verbose_name_plural = "03-作者表"
        db_table = verbose_name_plural

for table in models.__all__:
    admin.site.register(getattr(models, table))

需要自己手动，对取出来的数据进行序列化后返回

class BookView(View):

        # 第一版 用.values JsonResponse实现序列化
        def get(self, request):
            book_list = Book.objects.values("id", "title", "category", "pub_time", "publisher")
            book_list = list(book_list)
            ret = []
            for book in book_list:
                # print(book)
                publisher_id = book["publisher"]
                publisher_obj = Publisher.objects.filter(id=publisher_id).first()

                book["publisher"] = {      # 将 publisher 对应的出版社，序列化
                    "id": publisher_id,
                    "title": publisher_obj.title
                }
                ret.append(book)
            # ret = json.dumps(book_list, ensure_ascii=False)  # json.dumps 不能处理日期格式数据
            # return HttpResponse(ret)

            # 使用JsonResponse 能帮我们处理
            return JsonResponse(ret, safe=False, json_dumps_params={"ensure_ascii": False})

 

class BookView(View):
      
    # 第二版 用django serializers实现序列化
    def get(self, request):
        book_list = Book.objects.all()
        ret = serializers.serialize("json", book_list, ensure_ascii=False)
        return HttpResponse(ret)

 序列化仍旧处于表层，第二级以下的数据显示为数字

DRF序列化

用DRF的序列化，要遵循框架的一些标准，

　　-- 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 pip install djangorestframework

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'SerDemo',
    'rest_framework',
]

序列化

from rest_framework import serializers

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

from rest_framework.views import APIView

from rest_framework.response import Response
from .serializers import BookSerializer  # 导入序列化类
class BookView(APIView):

    def get(self, request):
        book_obj = Book.objects.first()
        ret = BookSerializer(book_obj)
        # book_list = Book.objects.all()  # 拿到所有的对象
        # ret = BookSerializer(book_list, many=True)
        return Response(ret.data)

  ret = BookSerializer(book_list, many=True)  序列化多个对象时，需要设置many=True

含外键数据的序列化

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)
    CHOICES = ((1, "Python"), (2, "Go"), (3, "Linux"))
    category = serializers.ChoiceField(choices=CHOICES, source="get_category_display")
    pub_time = serializers.DateField()

    publisher = PublisherSerializer()
    author = AuthorSerializer(many=True)

DRF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
将前端传过来的数据进行反序列化，然后保存到数据库

read_only=True #序列化
write_only=True #反序列化数据

前端传过来的数据样式

{
    "title": "Alex的使用教程",
    "w_category": 1,
    "pub_time": "2018-10-09",
    "publisher_id": 1,
    "author_list": [1, 2]
}

接受Post前端传过来的数据，必须在serialise类定义create方法

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(required=False)  #不需要校验
    title = serializers.CharField(max_length=32, validators=[my_validate])
    CHOICES = ((1, "Python"), (2, "Go"), (3, "Linux"))
    category = serializers.ChoiceField(choices=CHOICES, source="get_category_display", read_only=True)
    w_category = serializers.ChoiceField(choices=CHOICES, write_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    publisher_id = serializers.IntegerField(write_only=True)
    author = AuthorSerializer(many=True, read_only=True)
    author_list = serializers.ListField(write_only=True) #反序列化字段

    def create(self, validated_data): # 创建数据，接受post 数据
        book = Book.objects.create(title=validated_data["title"], category=validated_data["w_category"],
                                pub_time=validated_data["pub_time"], publisher_id=validated_data["publisher_id"])  # 取数据的时候应该为前端传过来的字段数据
        book.author.add(*validated_data["author_list"]) #多对多
        return book

定义 post 方法接受前端传过来的数据

class BookView(APIView):

    def get(self, request):
        # book_obj = Book.objects.first()
        # ret = BookSerializer(book_obj)
        book_list = Book.objects.all()
        ret = BookSerializer(book_list, many=True)
        return Response(ret.data)

    def post(self, request):
        print(request.data)
        serializer = BookSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)  #校验成功，反回
        else:
            return Response(serializer.errors)

post数据

反回的结果

DRF的PUT请求部分验证

单条数据操作

from django.urls import path, include
from .views import BookView, BookEditView

urlpatterns = [
    path('list', BookView.as_view()),
    path('retrieve/<int:id>', BookEditView.as_view()),

]

BookEditView

class BookEditView(APIView):

    def get(self, request, id):  # 获取单条数据
        book_obj = Book.objects.filter(id=id).first()
        ret = BookSerializer(book_obj)
        return Response(ret.data)

    def put(self, request, id):  # 部分修改数据
        book_obj = Book.objects.filter(id=id).first()
        serializer = BookSerializer(book_obj, data=request.data, partial=True) # partial=True # 支持部分验证
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        else:
            return Response(serializer.errors)

    def delete(self, request, id):
        book_obj = Book.objects.filter(id=id).first()
        book_obj.delete()
        return Response("")

查看单条数据，获取id为4的数据

修改数据

前端传过来的数据

data = {
    "title": "Alex的使用教程2"
}

对修改的数据进行序列化处理 update 方法

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(required=False)  #不需要校验
    title = serializers.CharField(max_length=32, validators=[my_validate])
    CHOICES = ((1, "Python"), (2, "Go"), (3, "Linux"))
    category = serializers.ChoiceField(choices=CHOICES, source="get_category_display", read_only=True)
    w_category = serializers.ChoiceField(choices=CHOICES, write_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    publisher_id = serializers.IntegerField(write_only=True)
    author = AuthorSerializer(many=True, read_only=True)
    author_list = serializers.ListField(write_only=True)

    def update(self, instance, validated_data):   # 处理 put 更新数据
        instance.title = validated_data.get("title", instance.title)
        instance.category = validated_data.get("category", instance.category)
        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("author_list"):
            instance.author.set(validated_data["author_list"])
        instance.save()
        return instance

反回的结果

DRF的验证

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(required=False)  # 不需要校验
    title = serializers.CharField(max_length=32, validators=[my_validate])
    CHOICES = ((1, "Python"), (2, "Go"), (3, "Linux"))
    category = serializers.ChoiceField(choices=CHOICES, source="get_category_display", read_only=True)
    w_category = serializers.ChoiceField(choices=CHOICES, write_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    publisher_id = serializers.IntegerField(write_only=True)
    author = AuthorSerializer(many=True, read_only=True)
    author_list = serializers.ListField(write_only=True)

    def create(self, validated_data):  # 创建数据
        book = Book.objects.create(title=validated_data["title"], category=validated_data["w_category"],
                                   pub_time=validated_data["pub_time"], publisher_id=validated_data["publisher_id"])
        book.author.add(*validated_data["author_list"])  # 多对多
        return book

    def update(self, instance, validated_data):  # 处理 put 更新数据
        instance.title = validated_data.get("title", instance.title)
        instance.category = validated_data.get("category", instance.category)
        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("author_list"):
            instance.author.set(validated_data["author_list"])
        instance.save()
        return instance

    def validate_title(self, value):   # 对传过来的title进行校验
        if "python" not in value.lower():
            raise serializers.ValidationError("标题必须含有python")
        return value

    def validate(self, attrs):  # 全局校验
        if attrs["w_category"] == 1 and attrs["publisher_id"] == 1:
            return attrs
        else:
            raise serializers.ValidationError("分类以及标题不符合要求")

自定义验证器

当有重叠校验器时自定义的验证器权重更高

def my_validate(value):  # 自定义验证器，权重更高，用在需要校验数据的地方
    if "敏感信息" in value.lower():
        raise serializers.ValidationError("不能含有敏感信息")
    else:
        return value

使用

title = serializers.CharField(max_length=32, validators=[my_validate])

 all

from rest_framework import serializers
from .models import Book


# 外键序列化
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)


#
# # 传过来的书籍对象数据
# book_obj = {
#     "title": "Alex的使用教程",
#     "w_category": 1,
#     "pub_time": "2018-10-09",
#     "publisher_id": 1,
#     "author_list": [1, 2]
# }
#
# data = {
#     "title": "Alex的使用教程2"
# }


def my_validate(value):  # 自定义验证器，权重更高，
    if "敏感信息" in value.lower():
        raise serializers.ValidationError("不能含有敏感信息")
    else:
        return value


class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(required=False)  # 不需要校验
    title = serializers.CharField(max_length=32, validators=[my_validate])
    CHOICES = ((1, "Python"), (2, "Go"), (3, "Linux"))
    category = serializers.ChoiceField(choices=CHOICES, source="get_category_display", read_only=True)
    w_category = serializers.ChoiceField(choices=CHOICES, write_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    publisher_id = serializers.IntegerField(write_only=True)
    author = AuthorSerializer(many=True, read_only=True)
    author_list = serializers.ListField(write_only=True)
#
    def create(self, validated_data):  # 创建数据
        book = Book.objects.create(title=validated_data["title"], category=validated_data["w_category"],
                                   pub_time=validated_data["pub_time"], publisher_id=validated_data["publisher_id"])
        book.author.add(*validated_data["author_list"])  # 多对多
        return book
#
    def update(self, instance, validated_data):  # 处理 put 更新数据
        instance.title = validated_data.get("title", instance.title)
        instance.category = validated_data.get("category", instance.category)
        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("author_list"):
            instance.author.set(validated_data["author_list"])
        instance.save()
        return instance

    def validate_title(self, value):  # 对传过来的title进行校验
        if "python" not in value.lower():
            raise serializers.ValidationError("标题必须含有python")
        return value

    def validate(self, attrs):
        if attrs["w_category"] == 1 and attrs["publisher_id"] == 1:
            return attrs
        else:
            raise serializers.ValidationError("分类以及标题不符合要求")

ModelSerializer序列化

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

# 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

# depth = 1 #对第二级别的字段也进行序列化

class BookSerializer(serializers.ModelSerializer):
    category = serializers.CharField(source="get_category_display")
    class Meta:
        model = Book  # 对应的 model
        # fields = ["id", "title", "pub_time"]
        fields = "__all__"  # 所有字段
        depth = 1  # 外键深度为1

拿到了较多的冗余字段

通过 SerializerMethodField 只取想要的字段，然后在下面定义各自的获取方法

自定义字段

class BookSerializer(serializers.ModelSerializer):

    # 只取想要的字段，
    category_display = serializers.SerializerMethodField(read_only=True)
    publisher_info = serializers.SerializerMethodField(read_only=True)
    authors = serializers.SerializerMethodField(read_only=True)

    def get_category_display(self, obj):
        return obj.get_category_display()

    def get_authors(self, obj):
        authors_query_set = obj.author.all()
        return [{"id": author_obj.id, "name": author_obj.name} for author_obj in authors_query_set]

    def get_publisher_info(self, obj):
        # obj 是我们序列化的每个Book对象
        publisher_obj = obj.publisher
        return {"id": publisher_obj.id, "title": publisher_obj.title}

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,]}}

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,]}}

 

ModelSerializer反序列化

ModelSerializer 默认已经帮我们做了反序列化（不用写 create 方法）接受post 数据

class BookSerializer(serializers.ModelSerializer):

    # 只取想要的字段，
    category_display = serializers.SerializerMethodField(read_only=True)     # 序列化（显示的时候）的 显示
    publisher_info = serializers.SerializerMethodField(read_only=True)
    authors = serializers.SerializerMethodField(read_only=True)

    # 定义获取字段的方法
    def get_category_display(self, obj):
        return obj.get_category_display()


    def get_authors(self, obj):
        authors_query_set = obj.author.all()
        return [{"id": author_obj.id, "name": author_obj.name} for author_obj in authors_query_set]

    def get_publisher_info(self, obj):
        # obj 是我们序列化的每个Book对象
        publisher_obj = obj.publisher
        return {"id": publisher_obj.id, "title": publisher_obj.title}

    # category = serializers.CharField(source="get_category_display")
    class Meta:
        model = Book  # 对应的 model
        # fields = ["id", "title", "pub_time"]
        fields = "__all__"
        # depth = 1

        # 字段的额外参数， "write_only": True 让下面这字段在反序列化的时候显示
        extra_kwargs = {"category": {"write_only": True}, "publisher": {"write_only": True},
                        "author": {"write_only": True}}

from rest_framework import serializers
from .models import Book


# 外键序列化
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)


#
# # 传过来的书籍对象数据
# book_obj = {
#     "title": "Alex的使用教程",
#     "w_category": 1,
#     "pub_time": "2018-10-09",
#     "publisher_id": 1,
#     "author_list": [1, 2]
# }
#
# data = {
#     "title": "Alex的使用教程2"
# }


def my_validate(value):  # 自定义验证器，权重更高，
    if "敏感信息" in value.lower():
        raise serializers.ValidationError("不能含有敏感信息")
    else:
        return value


# class BookSerializer(serializers.Serializer):
#     id = serializers.IntegerField(required=False)  # 不需要校验
#     title = serializers.CharField(max_length=32, validators=[my_validate])
#     CHOICES = ((1, "Python"), (2, "Go"), (3, "Linux"))
#     category = serializers.ChoiceField(choices=CHOICES, source="get_category_display", read_only=True)
#     w_category = serializers.ChoiceField(choices=CHOICES, write_only=True)
#     pub_time = serializers.DateField()
#
#     publisher = PublisherSerializer(read_only=True)
#     publisher_id = serializers.IntegerField(write_only=True)
#     author = AuthorSerializer(many=True, read_only=True)
#     author_list = serializers.ListField(write_only=True)
#
#     def create(self, validated_data):  # 创建数据
#         book = Book.objects.create(title=validated_data["title"], category=validated_data["w_category"],
#                                    pub_time=validated_data["pub_time"], publisher_id=validated_data["publisher_id"])
#         book.author.add(*validated_data["author_list"])  # 多对多
#         return book
#
#     def update(self, instance, validated_data):  # 处理 put 更新数据
#         instance.title = validated_data.get("title", instance.title)
#         instance.category = validated_data.get("category", instance.category)
#         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("author_list"):
#             instance.author.set(validated_data["author_list"])
#         instance.save()
#         return instance
#
#     def validate_title(self, value):  # 对传过来的title进行校验
#         if "python" not in value.lower():
#             raise serializers.ValidationError("标题必须含有python")
#         return value
#
#     def validate(self, attrs):
#         if attrs["w_category"] == 1 and attrs["publisher_id"] == 1:
#             return attrs
#         else:
#             raise serializers.ValidationError("分类以及标题不符合要求")

# 方法二
class BookSerializer(serializers.ModelSerializer):

    # 只取想要的字段，
    category_display = serializers.SerializerMethodField(read_only=True)     # 序列化（显示的时候）的 显示
    publisher_info = serializers.SerializerMethodField(read_only=True)
    authors = serializers.SerializerMethodField(read_only=True)

    # 定义获取字段的方法
    def get_category_display(self, obj):
        return obj.get_category_display()


    def get_authors(self, obj):
        authors_query_set = obj.author.all()
        return [{"id": author_obj.id, "name": author_obj.name} for author_obj in authors_query_set]

    def get_publisher_info(self, obj):
        # obj 是我们序列化的每个Book对象
        publisher_obj = obj.publisher
        return {"id": publisher_obj.id, "title": publisher_obj.title}

    # category = serializers.CharField(source="get_category_display")
    class Meta:
        model = Book  # 对应的 model
        # fields = ["id", "title", "pub_time"]
        fields = "__all__"
        # depth = 1

        # 字段的额外参数， "write_only": True 反序列化的时候显示
        extra_kwargs = {"category": {"write_only": True}, "publisher": {"write_only": True},
                        "author": {"write_only": True}}

序列化组件小结