Serialzers 序列化組件

前言

當作先後端分離的項目時，JSON是一個輕量級的數據交互格式。全部咱們給前端數據的時候都要轉成json格式，那就須要對咱們從數據庫拿到數據進行序列化

Django的序列化方法

使用django，json轉數據進行傳輸，（瞭解便可）

class BooksView(View):
    def get(self, request):
    	# 獲取數據庫中的queryset數據
        book_list = Book.objects.values("id", "title", "chapter", "pub_time", "publisher")
        # 強轉成列表類型
        book_list = list(book_list)
        # 若是咱們須要取外鍵關聯的字段信息 須要循環獲取外鍵 再去數據庫查而後拼接成咱們想要的
        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)

因爲太過於麻煩，全部咱們可使用DRF的序列化

字段和選項

注意serializer不是隻能爲數據庫模型類定義，也能夠爲非數據庫模型定義。serializer是獨立於數據庫以外的存在

1.字段和選項

<table style="border-spacing: 0px; font-size: 16px; color: #333333; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; letter-spacing: .2px; background-color: #ffffff;"> <thead> <tr style="border-top-color: #cccccc;"><th>字段</th><th>字段構造方式</th></tr> </thead> <tbody> <tr style="border-top-color: #cccccc;"> <td>BooleanField</td> <td>BooleanField()</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>NullBooleanField</td> <td>NullBooleanField()</td> </tr> <tr style="border-top-color: #cccccc;"> <td>CharField</td> <td>CharField(max_length=None, min_length=None, allow_blank=False, trim_whitespace=True)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>EmailField</td> <td>EmailField(max_length=None, min_length=None, allow_blank=False)</td> </tr> <tr style="border-top-color: #cccccc;"> <td>RegexField</td> <td>RegexField(regex, max_length=None, min_length=None, allow_blank=False)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>SlugField</td> <td>SlugField(maxlength=50, min_length=None, allow_blank=False)  正則字段，驗證正則模式 [a-zA-Z0-9-]+</td> </tr> <tr style="border-top-color: #cccccc;"> <td>URLField</td> <td>URLField(max_length=200, min_length=None, allow_blank=False)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>UUIDField</td> <td>UUIDField(format='hex_verbose')  format:  1) <code style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: .85em; border: none; color: inherit; background-color: #f7f7f7;">'hex_verbose'</code> 如<code style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: .85em; border: none; color: inherit; background-color: #f7f7f7;">"5ce0e9a5-5ffa-654b-cee0-1238041fb31a"</code>  2） <code style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: .85em; border: none; color: inherit; background-color: #f7f7f7;">'hex'</code> 如 <code style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: .85em; border: none; color: inherit; background-color: #f7f7f7;">"5ce0e9a55ffa654bcee01238041fb31a"</code>  3）<code style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: .85em; border: none; color: inherit; background-color: #f7f7f7;">'int'</code> - 如: <code style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: .85em; border: none; color: inherit; background-color: #f7f7f7;">"123456789012312313134124512351145145114"</code>  4）<code style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: .85em; border: none; color: inherit; background-color: #f7f7f7;">'urn'</code> 如: <code style="font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: .85em; border: none; color: inherit; background-color: #f7f7f7;">"urn:uuid:5ce0e9a5-5ffa-654b-cee0-1238041fb31a"</code></td> </tr> <tr style="border-top-color: #cccccc;"> <td>IPAddressField</td> <td>IPAddressField(protocol='both', unpack_ipv4=False, **options)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>IntegerField</td> <td>IntegerField(max_value=None, min_value=None)</td> </tr> <tr style="border-top-color: #cccccc;"> <td>FloatField</td> <td>FloatField(max_value=None, min_value=None)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>DecimalField</td> <td>DecimalField(max_digits, decimal_places, coerce_to_string=None, max_value=None, min_value=None) max_digits: 最多位數 decimal_palces: 小數點位置</td> </tr> <tr style="border-top-color: #cccccc;"> <td>DateTimeField</td> <td>DateTimeField(format=api_settings.DATETIME_FORMAT, input_formats=None)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>DateField</td> <td>DateField(format=api_settings.DATE_FORMAT, input_formats=None)</td> </tr> <tr style="border-top-color: #cccccc;"> <td>TimeField</td> <td>TimeField(format=api_settings.TIME_FORMAT, input_formats=None)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>DurationField</td> <td>DurationField()</td> </tr> <tr style="border-top-color: #cccccc;"> <td>ChoiceField</td> <td>ChoiceField(choices) choices與Django的用法相同</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>MultipleChoiceField</td> <td>MultipleChoiceField(choices)</td> </tr> <tr style="border-top-color: #cccccc;"> <td>FileField</td> <td>FileField(max_length=None, allow_empty_file=False, use_url=UPLOADED_FILES_USE_URL)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>ImageField</td> <td>ImageField(max_length=None, allow_empty_file=False, use_url=UPLOADED_FILES_USE_URL)</td> </tr> <tr style="border-top-color: #cccccc;"> <td>ListField</td> <td>ListField(child=, min_length=None, max_length=None)</td> </tr> <tr style="background-color: #f8f8f8; border-top-color: #cccccc;"> <td>DictField</td> <td>DictField(child=)</td> </tr> </tbody> </table>html

2.選項參數

3.通用參數

<table style="border-spacing:0px;font-size:16px;color:rgb(51,51,51);font-family:'Helvetica Neue', Helvetica, Arial, sans-serif;letter-spacing:.2px;background-color:rgb(255,255,255);"><thead><tr style="border-top-color:rgb(204,204,204);"><th>參數名稱</th><th>說明</th></tr></thead><tbody><tr style="border-top-color:rgb(204,204,204);"><td>read_only</td><td>代表該字段僅用於序列化輸出，默認False</td></tr><tr style="background-color:rgb(248,248,248);border-top-color:rgb(204,204,204);"><td>write_only</td><td>代表該字段僅用於反序列化輸入，默認False</td></tr><tr style="border-top-color:rgb(204,204,204);"><td>required</td><td>代表該字段在反序列化時必須輸入，默認True</td></tr><tr style="background-color:rgb(248,248,248);border-top-color:rgb(204,204,204);"><td>default</td><td>反序列化時使用的默認值</td></tr><tr style="border-top-color:rgb(204,204,204);"><td>allow_null</td><td>代表該字段是否容許傳入None，默認False</td></tr><tr style="background-color:rgb(248,248,248);border-top-color:rgb(204,204,204);"><td>validators</td><td>該字段使用的驗證器</td></tr><tr style="border-top-color:rgb(204,204,204);"><td>error_messages</td><td>包含錯誤編號與錯誤信息的字典</td></tr><tr style="background-color:rgb(248,248,248);border-top-color:rgb(204,204,204);"><td>label</td><td>用於HTML展現API頁面時，顯示的字段名稱</td></tr><tr style="border-top-color:rgb(204,204,204);"><td>help_text</td><td>用於HTML展現API頁面時，顯示的字段幫助提示信息</td></tr></tbody></table>python

DRF序列化的方法

1. 自定義序列化

須要自定義全部字段，以及方法create，updata方法git

聲明一個序列化類數據庫

# 根據model.py中的字段對應寫要顯示的字段
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()

將數據庫中的數據傳入序列化對象中django

from rest_framework.views import APIView
from rest_framework.response import Response

class BookView(APIView):
    def get(self, request):
        # 獲取數據庫中的數據
        book_list = Book.objects.all()
        # 實例化序列化對象， many= True 表示數據有多個，若是是一個則不須要
        ret = BookSerializer(book_list, many=True)
        # 給前端的數據
        return Response(ret.data)

2. 外鍵關係的序列化

from rest_framework import serializers
from .models import Book


class PublisherSerializer(serializers.Serializer):
    # read_only=True  表示的是給前端時顯示，反序列時，不須要此字段
    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)
    # many= True 表示有多條數據
    user = UserSerializer(many=True, read_only=True)

3. 反序列化

當前端給咱們發post請求的時候，前端給後端傳數據的，咱們須要對數據進行一些校驗而後保存到數據庫，或者對數據庫中的數據進行更改，DRF的serializer也提供了方法json
Serializer提供了is_valid()和save方法後端

url.pyapi

urlpatterns = [
    url(r'^list$', BooksView.as_view()),
]

聲明一個序列化類app

# serializers.py 文件
class BookSerializer(serializers.Serializer):
    # read_only = True  表示前端不須要傳該字段的數據，其餘的都須要傳
    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)
    # write_only = True 表示前端須要傳這個字段的數據，  
    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)
# post請求會執行該方法
    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"])
        # 須要返回對象
        # 若是數據簡單，
        # book = Book.objects.create(**validated_data)
        return book

注意：由於存在後端給前端顯示的數據和前端給後端存儲的數據有區別，全部要靈活運用read_only= True 和write_only=True ，倆個屬性，

反序列化

class BookView(APIView):
    def get(self, request):
        book_list = Book.objects.all()
        ret = BookSerializer(book_list, many=True)
        return Response(ret.data)
    # 會執行序列化中的create方法
    def post(self, request):
        # book_obj = request.data
        print(request.data)
        # 將前端傳來的數據傳入序列化對象中
        serializer = BookSerializer(data=request.data)
        # 判斷數據
        if serializer.is_valid():
            # 執行後端的create方法
            serializer.save()
            return Response(serializer.validated_data)
        # 不然將錯誤信息發回給前端
        return Response(serializer.errors)

對數據進行編輯

url.py

urlpatterns = [
    url(r'book/(?P<pk>\d+)/', BookView.as_view(), name='book'),
]

聲明一個序列化類

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
# put或者patch或執行該方法
    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.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()
        # partial= True 對部分數據進行修改
        serializer = BookSerializer(book_obj, data=book_info, partial=True)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        else:
            return Response(serializer.errors)

     # 這倆種方法是同樣的只寫其中一種
    def put(self, request, id):
        book_obj = Book.objects.filter(id=id).first()
        ser_obj = BookSerializer(instance=book_obj, data=request.data, partial=True)
        if ser_obj.is_valid():
            ser_obj.save()
            return Response(ser_obj.data)
        return Response(ser_obj.errors)

3.1 view四個方法的運用

-- get 請求
   def get(self, request):
      queryset = Book.objects.all()
      ser_obj = BookSerializer(queryset, many=True)
      return Response(ser_obj.data)


-- post請求
   def post(self, request):
      data = request.data
      ser_obj = BookSerializer(data=request.data)
      if ser_obj.is_valid():
         ser_obj.save()
         # ser_obj.validated_data
         return Response(ser_obj.data)
      else:
         return Response(ser_obj.errors)
        
        
-- put/patch請求
   def put(self, request, id):
      data = request.data
      book_obj = Book.objects.filter(id=id).first()
      ser_obj = BookSerializer(instance=book_obj, data=request.data, partial=True)  # partial表示局部更新
      if ser_obj.is_valid():
         ser_obj.save()
         # ser_obj.validated_data
         return Response(ser_obj.data)
      else:
         return Response(ser_obj.errors)

4.驗證

優先級從高到低：自定義>單獨驗證>多個字段驗證
若是咱們須要對某些字段進行自定義驗證，DRF也給咱們提供了鉤子方法

一對單個數據進行驗證， 格式必須是validate_須要驗證的字段名(self, value)：

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)
    # 省略了一些字段 跟上面代碼裏同樣的
    # 。。。。。
    # 格式必須是validate_須要驗證的字段名(self, value)
     def validate_title(self, value):
        if "python" not in value.lower():
            raise serializers.ValidationError("標題必須含有Python")
        return value

對多個數據進行驗證

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長的
    # 。。。。。。

    # 對多個字段進行驗證 要求上架日期不能早於出版日期 上架日期要大
    def validate(self, attrs):
        if attrs["pub_time"] > attrs["date_added"]:
            raise serializers.ValidationError("上架日期不能早於出版日期")
        return attrs

定義一個驗證器

def my_validate(value):
    if "敏感詞彙" in value.lower:
        raise serializers.ValidationError("包含敏感詞彙，請從新提交")
    return value


class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32, validators=[my_validate])
    # 。。。。。。

ModelSerializer

如今咱們已經清楚了Serializer的用法，會發現咱們全部的序列化跟咱們的模型都緊密相關~

那麼，DRF也給咱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

　　-- 它簡單的默認實現了.update()以及.create()方法

1.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"]
        # 分別是全部字段 包含某些字段 排除某些字段

2.外鍵關聯的序列化

自動序列化連表操做，可使用depth來進行快捷的跨表操做，官方建議是0~10層，可是最好用到3或者4層就能夠了

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）則自動變爲只讀

class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分別是全部字段 包含某些字段 排除某些字段
        depth = 1
# depth 表明找嵌套關係的第幾層

3.自定義字段對覆蓋默認字段

咱們能夠聲明一些字段來覆蓋默認字段，來進行自定製~

好比咱們的選擇字段，默認顯示的是選擇的key，咱們要給用戶展現的是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"]
        # 分別是全部字段 包含某些字段 排除某些字段
        depth = 1

4.meta中的其它關鍵字參數

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"]
        # 分別是全部字段 包含某些字段 排除某些字段
        depth = 1
        # read_only_fields 表示只讀
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}

read_only_fields 表示id爲只讀，
extra_kwargs 選項在字段上指定任意附加關鍵字參數。與 read_only_fields 的狀況同樣，這意味着你不須要在序列化類中顯式聲明該字段。

該選項是一個字典，將字段名稱映射到關鍵字參數字典。例如：

class CreateUserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ('email', 'username', 'password')
        extra_kwargs = {'password': {'write_only': True}}

5 post以及patch/put請求

因爲depth會讓咱們外鍵變成只讀，因此咱們再定義一個序列化的類，其實只要去掉depth就能夠了~~

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"]
        # 分別是全部字段 包含某些字段 排除某些字段
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}

6 SerializerMethodField

針對於多對多表數據的顯示，可使用SerializerMethodField，來自定義顯示

外鍵關聯的對象有不少字段咱們是用不到的~都傳給前端會有數據冗餘~就須要咱們本身去定製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是當前序列化的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"]
        # 分別是全部字段 包含某些字段 排除某些字段
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}

7. 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是當前序列化的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"]
        # 分別是全部字段 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}}

返回URL的鏈接

詳情見網址：https://www.cnblogs.com/wupeiqi/articles/7805382.html中的序列化中的url