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)
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)
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()
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)
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)
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
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)
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
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)
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
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
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]) # 。。。。。。
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
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
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
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,]}}
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,]}}
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,]}}
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}}
