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
serializer:
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()
view:
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,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:
# 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
view:
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~~
Serializer:
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
view:
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~
Serializer:
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
view:
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}}