为什么要用序列化组件呢
当我们做前后端分离的项目~~我们前后端交互一般会选择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。
Django的序列化方法
1、.values 序列化结果
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)
2、django serializers
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中，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，JosnResponse，render，DRF我们用Response
序列化步骤
第一步、声明序列化类
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()
第二步、序列化对象
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
# 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)
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徐保存到数据库
这些校验以及保存工作，DRF的Serializer也给我们提供了一些方法
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
#反序列化serializer.py
# 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 views.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)
当前端给我们发送patch请求的时候，前端给我们用户要更新的数据，我们要对数据进行部分验证
PATCH请求 serializers.py
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 views.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.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
#单个字段的验证
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
#多个字段的验证
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
#验证器 validators
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
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中其他关键字参数
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
#post/patch 请求序列化类
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，都传输给前端的话就会有数据冗余，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}}