為什麼要用序列化元件
當我們做前後端分離的項目,我們前後端互動一般都選擇JSON資料格式,JSON是一個輕量級的資料互動格式。
那麼我們給前端資料的時候都要轉成json格式,那就需要對我們從資料庫拿到的資料進行序列化。
接下來我們看下django序列化和rest_framework序列化的對比
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)
# 如果我們需要取外鍵關聯的字段資訊 需要循環擷取外鍵 再去資料庫查然後拼接成我們想要的
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()
# 解決json不能序列化時間字段的問題
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
# 能夠得到我們要的效果 結構有點複雜
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,我們要用DRF的序列化,就要遵循人家架構的一些标準,
- Django我們CBV繼承類是View,現在DRF我們要用APIView
- Django中傳回的時候我們用HTTPResponse,JsonResponse,render ,DRF我們用Response
為什麼這麼用~我們之後會詳細講我們繼續來看序列化
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)
外鍵關系的序列化
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
目前端給我們發post的請求的時候,我們要進行一些校驗然後儲存到資料庫
這些校驗以及儲存工作,DRF的Serializer也給我們提供了一些方法了
首先~我們要寫反序列化用的一些字段~有些字段要跟序列化區分開
Serializer提供了.is_valid() 和.save()方法
serializers:
# serializers.py 檔案
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)
目前端給我們發送patch請求的時候,前端傳給我們使用者要更新的資料,我們要對資料進行部分驗證~~
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)
驗證
如果我們需要對一些字段進行自定義的驗證~DRF也給我們提供了鈎子方法~~
Serializer:
class BookSerializer(serializers.Serializer):
id = serializers.IntegerField(read_only=True)
title = serializers.CharField(max_length=32)
# 省略了一些字段 跟上面代碼裡一樣的
# 。。。。。
def validate_title(self, value):
if "python" not in value.lower():
raise serializers.ValidationError("标題必須含有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)
# 新增了一個上架時間字段
# 省略一些字段。。都是在原基礎代碼上增加的
# 。。。。。。
# 對多個字段進行驗證 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 "敏感詞彙" in value.lower:
raise serializers.ValidationError("包含敏感詞彙,請重新送出")
return value
class BookSerializer(serializers.Serializer):
id = serializers.IntegerField(read_only=True)
title = serializers.CharField(max_length=32, validators=[my_validate])
# 。。。。。。
ModelSerializer
現在我們已經清楚了Serializer的用法,會發現我們所有的序列化跟我們的模型都緊密相關~
那麼,DRF也給我們提供了跟模型緊密相關的序列化器ModelSerializer
- 它會根據模型自動生成一組字段
- 它簡單的預設實作了.update()以及.create()方法
定義一個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
外鍵關系的序列化
注意:當序列化類MATE中定義了depth時,這個序列化類中引用字段(外鍵)則自動變為隻讀
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 代表找嵌套關系的第幾層
自定義字段
我們可以聲明一些字段來覆寫預設字段,來進行自定制~
比如我們的選擇字段,預設顯示的是選擇的key,我們要給使用者展示的是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中其它關鍵字參數
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請求
由于depth會讓我們外鍵變成隻讀,是以我們再定義一個序列化的類,其實隻要去掉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
外鍵關聯的對象有很多字段我們是用不到的~都傳給前端會有資料備援~就需要我們自己去定制序列化外鍵對象的哪些字段~~
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是目前序列化的book對象
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改進上面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是目前序列化的book對象
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}}
轉載于:https://www.cnblogs.com/huang-yc/p/10432830.html