drf serializer - Serializer

Python之drf序列化器-Serializer

一、序列化器-Serializer的作用

• 序列化,The serializer converts model class objects into dictionaries,经过Response变成json字符串
• 反序列化,data sent by the client,经过request以后变成字典,Serializers can convert dictionaries into models
• 反序列化,Verify the legitimacy of the data sent by the client

二、定义序列化器

• Django REST framework中的Serializer使用类来定义,须继承自rest_framework.serializers.Serializer.

You need to create a model class in the database first（建表）

from django.db import models

# Create your models here.
class Student(models.Model):
    name = models.CharField(max_length=32)
    age = models.IntegerField()

在应用下新建serializer.py文件（名字可以随意取,一般使用serializer）,在文件中导入刚才建立的表并导入serializers.如下

from rest_framework import serializers
from .models import Student
# 定义序列化器
class StudentSerializer(serializers.Serializer):
    # Write the field name you want to serialize below
    name = serializers.CharField()
    age = serializers.IntegterField()

The above is done as soon as a serialization class is written,下一步在view.pyFill in the corresponding code in the view function.如下

from django.shortcuts import render

# Create your views here.
import models
from rest_framework.views import APIView
from rest_framework.response import Response
from .serializers import StudentSerializes

class Student(APIView);
	def get(self,request):
        back_dic = {
    'code':200,'msg':'成功','result':''}
        queryset_obj = models.Student.objects.all()
        res = StudentSerializers(instance=query_obj,many=True)
        if not res.is_valid():
            back_dic['code'] = 1001
            back_dic['msg'] = '失败'
            return Response(back_dic)
        back_dic['result'] = res.data
        return Response(back_dic)
    

此时使用postmanWhen the interface is called, the data stored in the database can be obtained and the data is obtainedjsonformat sent to the front end

This data is from a dictionary orQueryset对象转为json的操作,is the serialization classStudentSerializes做的

# Serializer的构造方法为：
Serializer(instance=None, data=empty, **kwarg)
""" 1）用于序列化时,将模型类对象传入instance参数 2）用于反序列化时,将要被反序列化的数据传入data参数 3）除了instance和data参数外,在构造Serializer对象时,还可通过context参数额外添加数据 """
serializer = AccountSerializer(account, context={
    'request': request})
""" 1、使用序列化器的时候一定要注意,序列化器声明了以后,不会自动执行,需要我们在视图中进行调用才可以. 2、序列化器无法直接接收数据,需要我们在视图中创建序列化器对象时把使用的数据传递过来. 3、序列化器的字段声明类似于我们前面使用过的表单系统. 4、开发restful api时,序列化器会帮我们把模型数据转换成字典. 5、drf提供的视图会帮我们把字典转换成json,或者把客户端发送过来的数据转换字典. """

**注意：serializer不是只能为数据库模型类定义,也可以为非数据库模型类的数据定义.serializer是独立于数据库之外的存在.

三、Serializer common fields and their parameters

常用字段：

字段	字段构造方式
BooleanField	BooleanField()
NullBooleanField	NullBooleanField()
CharField	CharField(max_length=None, min_length=None, allow_blank=False, trim_whitespace=True)
EmailField	EmailField(max_length=None, min_length=None, allow_blank=False)
RegexField	RegexField(regex, max_length=None, min_length=None, allow_blank=False)
SlugField	SlugField(maxlength=50, min_length=None, allow_blank=False) 正则字段,验证正则模式 [a-zA-Z0-9-]+
URLField	URLField(max_length=200, min_length=None, allow_blank=False)
UUIDField	UUIDField(format=’hex_verbose’) format: 1) 'hex_verbose' 如"5ce0e9a5-5ffa-654b-cee0-1238041fb31a" 2） 'hex' 如 "5ce0e9a55ffa654bcee01238041fb31a" 3）'int' - 如: "123456789012312313134124512351145145114" 4）'urn' 如: "urn:uuid:5ce0e9a5-5ffa-654b-cee0-1238041fb31a"
IPAddressField	IPAddressField(protocol=’both’, unpack_ipv4=False, **options)
IntegerField	IntegerField(max_value=None, min_value=None)
FloatField	FloatField(max_value=None, min_value=None)
DecimalField	DecimalField(max_digits, decimal_places, coerce_to_string=None, max_value=None, min_value=None) max_digits: 最多位数 decimal_palces: 小数点位置
DateTimeField	DateTimeField(format=api_settings.DATETIME_FORMAT, input_formats=None)
DateField	DateField(format=api_settings.DATE_FORMAT, input_formats=None)
TimeField	TimeField(format=api_settings.TIME_FORMAT, input_formats=None)
DurationField	DurationField()
ChoiceField	ChoiceField(choices) choices与Django的用法相同
MultipleChoiceField	MultipleChoiceField(choices)
FileField	FileField(max_length=None, allow_empty_file=False, use_url=UPLOADED_FILES_USE_URL)
ImageField	ImageField(max_length=None, allow_empty_file=False, use_url=UPLOADED_FILES_USE_URL)
ListField	ListField(child=, min_length=None, max_length=None)
DictField	DictField(child=)

选项参数：

参数名称	作用
max_length	最大长度
min_lenght	最小长度
allow_blank	是否允许为空
trim_whitespace	是否截断空白字符
max_value	最小值
min_value	最大值

通用参数：

参数名称	说明
read_only	表明该字段仅用于序列化输出,默认False
write_only	表明该字段仅用于反序列化输入,默认False
required	表明该字段在反序列化时必须输入,默认True
default	反序列化时使用的默认值
allow_null	表明该字段是否允许传入None,默认False
validators	该字段使用的验证器
error_messages	包含错误编号与错误信息的字典
label	用于HTML展示API页面时,显示的字段名称
help_text	用于HTML展示API页面时,显示的字段帮助提示信息·1·

四、Serializer advanced usage

1、source用法

from rest_framework import serializers
from .models import Student
# 定义序列化器
class StudentSerializer(serializers.Serializer):
    # Write the field name you want to serialize below
    name = serializers.CharField()
    age = serializers.IntegterField()

Serialization abovename字段中,This can be used if you don't want the front end to see the actual fields in your tablesource方法,

soucreThe method is that the current name is mapped to a field in this table,In this way, the current name can get the value of the mapped field in the table in the front end,如下

name1 = serializers.CharField(source='name',read_only=True )
name = serializers.ChsrField(write_only=True)

常配合read_only与write_only使用

2、serializers.SerializerMethodField用法

SerializerMethodFieldThe display style of serialized fields can be specified

• 在django2.0以上,It needs to be added when the fields of the model class are associated with other keyson_delete=models.CASCADE（级联删除）

# new model sheet
from django.db import models

# Create your models here.
class Student(models.Model):
    name = models.CharField(max_length=32)
    age = models.IntegerField()
    publish = models.ForeignKey(to='publish',on_delete=models.CASCADE)
class Publish(model.Model):
    name = models.CharField(max_length=32)
    addr = models.CharField(max_length=256)

Fields associated with foreign keys are in the front end（postman）is shown in the object

SerializerMethodFieldmethod can be used to display detailed data associated with foreign keys

# 此时在serializer.py中就需要用到SerializerMethodField方法了
from rest_framework import serializers
from .models import Student
# 定义序列化器
class StudentSerializer(serializers.Serializer):
    # Write the field name you want to serialize below
    name = serializers.CharField()
    age = serializers.IntegterField()
    # 方法一(在序列化类中写)
	pulish = serializers.SerializerMethodField() # 缺点 Can only be used for serialization 默认就是read_only=True
    def get_publish(self,obj): # get_字段名
        # return obj.publish.name # Displays the publisher name
        return {
    'id':obj.publish.id,'name':obj.publish.name,'addr':obj.publish.addr} # Return to publisher details
    
    # 方式二(Write in the model class,方法返回什么,The fields below are what) 用的多
    pulish_detail = serializers.CharField() # This return to the front end is in the form of a dictionary,不是json格式的
    pulish_detail = serializers.DictField()  # 使用DictField返回的就是json格式
    # Write a property in the model class
    @property
    def pulish_detail(self):
        return {
    'id':self.publish.id,'name':self.publish.name,'addr':self.publish.addr}
    
    # 方式三(了解)
    pulish_detail = serializers.CharField(source='publish.name')

五、反序列化

一、数据验证

使用序列化器进行反序列化时,需要对数据进行验证后,才能获取验证成功的数据或保存成模型类对象.

在获取反序列化的数据前,必须调用**is_valid()**方法进行验证,验证成功返回True,否则返回False.

验证失败,可以通过序列化器对象的errors属性获取错误信息,返回字典,包含了字段和字段的错误.如果是非字段错误,可以通过修改REST framework配置中的NON_FIELD_ERRORS_KEY来控制错误字典中的键名.

验证成功,可以通过序列化器对象的validated_data属性获取数据.

在定义序列化器时,指明每个字段的序列化类型和选项参数,本身就是一种验证行为.

1、自定义验证

validate_字段名（也叫局部钩子）

# validate_字段名 Validate a single field
# Validate in the serialization class
def validate_name(self,value)
    if '草' in value:
                raise ValidationError('不符合社会主义核心价值观')
            return value

validate（也叫全局钩子）

# validateWhen comparing multiple fields at the same time,可以定义validate方法来验证
def validate(self, attrs):
        bread = attrs['bread']
        bcomment = attrs['bcomment']
        if bread < bcomment:
            raise serializers.ValidationError('阅读量小于评论量')
        return attrs

validators

# 在字段中添加validators选项参数,也可以补充验证行为,如
btitle = serializers.CharField(label='名称', max_length=20, validators=[about_django])

二、保存数据

After the previous verification data is successful,我们可以使用序列化器来完成数据反序列化的过程.这个过程可以把数据转成模型类对象.

可以通过重写create()和update()两个方法来实现

class BookInfoSerializer(serializers.Serializer):
    """图书数据序列化器"""
    ...

    def create(self, validated_data):
        """新建"""
        res = BookInfo.objects.create(**validated_data)
        return res

    def update(self, instance, validated_data):
        """更新,instance为要更新的对象实例"""
        instance.btitle = validated_data.get('btitle', instance.btitle)
        instance.bpub_date = validated_data.get('bpub_date', instance.bpub_date)
        instance.bread = validated_data.get('bread', instance.bread)
        instance.bcomment = validated_data.get('bcomment', instance.bcomment)
        instance.save()
        return instance

六、模型类序列化器

在上面的代码中,StudentSerializerSerializer and model classStudent是没有关系的.If light wrote oneStudentSerializer,There are multiple tables in the model classname字段的话,He will serialize all the tablesname字段.

下面使用ModelSerializerSerialization classes can be refactored,It is assigned to a certain class for use

from rest_framework import serializers
from .models import Book
class BookSerializers(serializers.ModelSerializers):
    # The corresponding relationship with the table needs to be specified
    class Meta:
        model = Book  # 必须叫model
    	# 指定要序列化的字段
        fields = ['name','price'] # The first is written as a list specifying the fields to serialize
        fields = '__all__'  # 第二种'__all__'Serialize all fields in the table
        """ 也可以使用exclude可以明确排除掉哪些字段 可以通过read_only_fields指明只读字段,即仅用于序列化输出的字段 """
        read_only_fields = ('id', 'bread', 'bcomment')

添加额外参数选项

我们可以使用extra_kwargs参数为ModelSerializer添加或修改原有的选项参数

class BookInfoSerializer(serializers.ModelSerializer):
    """图书数据序列化器"""
    class Meta:
        model = BookInfo
        fields = ('id', 'btitle', 'bpub_date', 'bread', 'bcomment')
        extra_kwargs = {
    
            'bread': {
    'min_value': 0, 'required': True},
            'bcomment': {
    'min_value': 0, 'required': True},
        }

depth

# When there is a foreign key in a relational table,When querying, the foreign key field value will appear as oneid号
# If you want the foreign key field to display detailed information, you need to be in
class Meta:
    ……
    depth=1 # 这个1Indicates the number of nesting levels 

七、习题

""" 1 定义两个表,Books and Publishers table -出版社的5个接口 -图书的5个接口 -查询的时候,Publisher shows details -Added and modified band publishers -The price is displayed as xx元 2 When adding a publisher,addr最大8,最小3,不能以sb开头,The address cannot contain a first name """

models.py

from django.db import models

# Create your models here.
class Book(models.Model):
    book_name = models.CharField(max_length=32,verbose_name='书名')
    book_price = models.IntegerField(verbose_name='价钱')
    publish = models.ForeignKey(to='Publish',on_delete=models.CASCADE)

    # Inquiry with publisher details Method 2(Write directly in the model class)
    @property
    def get_publish(self):
        return {
    'id':self.publish.id,'publish_name':self.publish.publish_name,'publish_addr':self.publish.publish_addr}

    # Inquiry price method 2(Write directly in the model class)
    @property
    def get_book_price(self):
        return str(self.book_price)+'元'

class Publish(models.Model):
    publish_name = models.CharField(max_length=32,verbose_name='出版社名称')
    publish_addr = models.CharField(max_length=255,verbose_name='出版社地址')

serializer.py

from rest_framework import serializers
from .models import Publish, Book
from rest_framework.exceptions import ValidationError  # The exception status package needs to be imported,djangoA global exception will be caught


class PublishModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = Publish
        fields = ['id', 'publish_name', 'publish_addr']
        # extra_kwargs = {
    
        # 'publish_addr': {'max_length': 8, 'min_length': 3, 'error_messages': {
    
        # 'min_length': '太短',
        # 'max_length': '太长'
        # }}
        # }

    #全局钩子
    def validate(self, attrs):
        print(attrs)
        if attrs.get('publish_addr').startswith('sb'):
            raise ValidationError('不符合社会主义核心价值观')
        if attrs.get('publish_name') in attrs['publish_addr']:
            raise ValidationError('The address cannot contain a first name')
        return attrs


class BookModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = ['id', 'book_name', 'book_price', 'publish', 'get_book_price', 'get_publish']
        extra_kwargs = {
    
            'id': {
    'read_only': True},
            'book_price': {
    'write_only': True},
            'publish': {
    'write_only': True}
        }

    # When deserializing, you want to accept onlybook_price,publishTwo fields can limit it towrite_only = True
    # book_price = serializers.IntegerField(write_only=True)
    # publish = serializers.IntegerField(write_only=True)

    # Inquiry with publisher details method 1
    # publish = serializers.SerializerMethodField()
    # def get_publish(self,obj):
    # return {'id':obj.publish.id,'publish_name':obj.publish.publish_name,'publish_addr':obj.publish.publish_addr}

    # The price is displayed as xxMeta method one
    # book_price = serializers.SerializerMethodField()
    # def get_book_price(self,obj):
    # return str(obj.book_price)+'元'

    # 序列化的时候使用book_price,publish,It is when deserializingobook_price,opublish
    # get_book_price = serializers.CharField(read_only=True)
    # get_publish = serializers.CharField(read_only=True)

views.py

from django.shortcuts import render

# Create your views here.
""" 1 定义两个表,Books and Publishers table -出版社的5个接口 -图书的5个接口 -查询的时候,Publisher shows details -Added and modified band publishers -The price is displayed as xx元 2 When adding a publisher,addr最大8,最小3,不能以sb开头,The address cannot contain a first name """
from app01 import models
from rest_framework.views import APIView
from .serializers import PublishModelSerializer,BookModelSerializer
from rest_framework.response import Response
from rest_framework.exceptions import ValidationError

# 出版社 无参
class publish(APIView):
    # Get all publisher interfaces
    def get(self,request):
        back_dic = {
    'code':200,'msg':'查询成功','result':''}
        res = models.Publish.objects.all()
        result = PublishModelSerializer(instance=res,many=True)

        back_dic['result'] = result.data
        return Response(back_dic)

    def post(self,request):
        back_dic = {
    'code': 200, 'msg': '新增成功', 'result': ''}
        result = PublishModelSerializer(data=request.data)

        if not result.is_valid():
            return Response(result.errors)

        result.save() # 保存数据
        back_dic['result'] = result.data
        return Response(back_dic)

# 有参
class publish_param(APIView):
    def get(self,request,**kwargs):
        back_dic = {
    'code': 200, 'msg': '查询成功', 'result': ''}
        res = models.Publish.objects.filter(**kwargs).first()
        result = PublishModelSerializer(instance=res)

        back_dic['result'] = result.data
        return Response(back_dic)

    def delete(self,request,**kwargs):
        back_dic = {
    'code': 200, 'msg': '删除成功'}
        models.Publish.objects.filter(**kwargs).delete()
        return Response(back_dic)

    def put(self,request,**kwargs):
        back_dic = {
    'code': 200, 'msg': '修改成功', 'result': ''}
        res = models.Publish.objects.filter(**kwargs).first()
        result = PublishModelSerializer(instance=res,data=request.data)

        if  result.is_valid() ==False:
            return Response(result.errors)

        result.save()
        back_dic['result'] = result.data
        return Response(back_dic)


# 书籍 无参
class Book(APIView):
    # Get all book interfaces
    def get(self, request):
        back_dic = {
    'code': 200, 'msg': '查询成功', 'result': ''}
        res = models.Book.objects.all()
        result = BookModelSerializer(instance=res, many=True)

        back_dic['result'] = result.data
        return Response(back_dic)

    def post(self, request):
        back_dic = {
    'code': 200, 'msg': '新增成功', 'result': ''}
        result = BookModelSerializer(data=request.data)

        if  not result.is_valid():
            return Response(result.errors)

        result.save()  # 保存数据
        back_dic['result'] = result.data
        return Response(back_dic)


class Book_param(APIView):
    def get(self,request,**kwargs):
        back_dic = {
    'code': 200, 'msg': '查询成功', 'result': ''}
        res = models.Book.objects.filter(**kwargs).first()
        result = BookModelSerializer(instance=res)

        back_dic['result'] = result.data
        return Response(back_dic)

    def delete(self,request,**kwargs):
        back_dic = {
    'code': 200, 'msg': '删除成功'}
        models.Book.objects.filter(**kwargs).delete()
        return Response(back_dic)

    def put(self,request,**kwargs):
        back_dic = {
    'code': 200, 'msg': '修改成功', 'result': ''}
        res = models.Book.objects.filter(**kwargs).first()
        result = BookModelSerializer(instance=res,data=request.data)

        if  result.is_valid() ==False:

            return Response(result.errors)

        result.save()
        back_dic['result'] = result.data
        return Response(back_dic)

urls.py

from django.contrib import admin
from django.urls import path
from app01 import views

urlpatterns = [
    path('admin/', admin.site.urls),

    # 出版社
    path('publish/', views.publish.as_view()),
    path('publish/<int:pk>', views.publish_param.as_view()),

    path('book/', views.Book.as_view()),
    path('book_param/<int:pk>', views.Book_param.as_view()),

]