Serializers 序列化组件-白红宇

Serializers 序列化组件

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发布时间：2019-06-23

本文共 12399 字，大约阅读时间需要 41 分钟。

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 APIViewfrom rest_framework.response import Responseclass 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

from rest_framework import serializersfrom .models import Bookclass 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 valueclass 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}}

ModelSerializer

转载于:https://www.cnblogs.com/MayDayTime/p/9890582.html

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