20-Django REST framework-Serializer序列化器

Serializer序列化器

- - 前言
  - 序列化器作用
  - 定义Serializer
  - - 定义方法
    - 字段与选项
    - 创建Serializer对象
  - 序列化使用
  - - 基本使用
    - 增加额外字段
    - 关联对象序列化
  - 反序列使用
  - 模型类序列化器ModelSerializer
  - - 指定字段

前言

本篇来学习Serializer序列化器知识

序列化器作用

进行数据的校验
对数据对象进行转换

定义Serializer

定义方法

模型

# models.py

from django.db import models


# Create your models here.
# 准备书籍列表信息的模型类
class BookInfo(models.Model):
    # 创建字段，字段类型
    name = models.CharField(max_length=20, verbose_name='名称')  # verbose_name admin管理后台使用
    pub_date = models.DateField(verbose_name='发布日期', null=True)
    readcount = models.IntegerField(default=0, verbose_name='阅读量')
    commentcount = models.IntegerField(default=0, verbose_name='评论量')
    is_delete = models.BooleanField(default=False, verbose_name='逻辑删除')

    class Meta:
        db_table = 'bookinfo'  # 指明数据库表名
        verbose_name = '图书'  # 在admin站点中显示的名称

    def __str__(self):
        """定义每个数据对象的显示信息"""
        return self.name

序列化器

# -*- coding: utf-8 -*-
# @Time    : 2022/9/24
# @Author  : 大海
# serializers.py

from rest_framework import serializers
from book.models import BookInfo

class BookInfoSerializer(serializers.Serializer):
    """图书数据序列化器"""
    name = serializers.CharField(max_length=20, label='名称')  # label DRF接口页面展示使用
    pub_date = serializers.DateField(label='发布日期', required=True)
    readcount = serializers.IntegerField(required=False, label='阅读量')
    commentcount = serializers.IntegerField(required=False, label='评论量')
    is_delete = serializers.BooleanField(required=False, label='逻辑删除')

字段与选项

常用字段类型
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

创建Serializer对象

Serializer的构造方法为：

Serializer(instance=None, data=empty, **kwarg)

说明：
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，如
serializer = AccountSerializer(account, context={‘request’: request})
通过context参数附加的数据，可以通过Serializer对象的context属性获取。

序列化使用

基本使用

进入Django shell模式

python manage.py shell

查询一个图书对象

from book.models import BookInfo

book = BookInfo.objects.get(id=1)

构造序列化器

from book.serializers import BookInfoSerializer

serializer = BookInfoSerializer(book)

获取序列化数据

serializer.data

如果要被序列化的是包含多条数据的查询集QuerySet，可以通过添加many=True参数补充说明

books = BookInfo.objects.all()
serializer = BookInfoSerializer(books,many=True)
serializer.data

在这里插入图片描述

增加额外字段

# serializers.py
from rest_framework import serializers

class BookInfoSerializer(serializers.Serializer):
    """图书数据序列化器"""
    name = serializers.CharField(max_length=20, label='名称')  # label DRF接口页面展示使用
    pub_date = serializers.DateField(label='发布日期', required=True)
    readcount = serializers.IntegerField(required=False, label='阅读量')
    commentcount = serializers.IntegerField(required=False, label='评论量')
    is_delete = serializers.BooleanField(required=False, label='逻辑删除')
    hello = serializers.CharField()  # 增加模型中不存在字段

进入Django shell模式

python manage.py shell

from book.models import BookInfo

book = BookInfo.objects.get(id=1)

book.hello = '666'

from book.serializers import BookInfoSerializer

serializer = BookInfoSerializer(book)

serializer.data

在这里插入图片描述

关联对象序列化

models.py

from django.db import models


# Create your models here.
# 准备书籍列表信息的模型类
class BookInfo(models.Model):
    # 创建字段，字段类型
    name = models.CharField(max_length=20, verbose_name='名称')  # verbose_name admin管理后台使用
    pub_date = models.DateField(verbose_name='发布日期', null=True)
    readcount = models.IntegerField(default=0, verbose_name='阅读量')
    commentcount = models.IntegerField(default=0, verbose_name='评论量')
    is_delete = models.BooleanField(default=False, verbose_name='逻辑删除')

    class Meta:
        db_table = 'bookinfo'  # 指明数据库表名
        verbose_name = '图书'  # 在admin站点中显示的名称
	
	def __str__(self):
        """定义每个数据对象的显示信息"""
        return self.name


# 准备人物列表信息的模型类
class PeopleInfo(models.Model):
    # 定义一个有序字典
    GENDER_CHOICES = (
        (0, 'male'),
        (1, 'female')
    )
    name = models.CharField(max_length=20, verbose_name='名称')
    gender = models.SmallIntegerField(choices=GENDER_CHOICES, default=0, verbose_name='性别')
    description = models.CharField(max_length=200, null=True, verbose_name='描述信息')
    is_delete = models.BooleanField(default=False, verbose_name='逻辑删除')
    # 外键 ForeignKey
    # 系统会字典为外加添加  id
    # 外键的级联操作  1对多 (书籍对人物)
    # CASCADE:删除主表数据时连通一起删除外键表中数据
    book = models.ForeignKey(BookInfo, on_delete=models.CASCADE, verbose_name='图书')

    class Meta:
        db_table = 'peopleinfo'
        verbose_name = '人物信息'

serializers.py

# -*- coding: utf-8 -*-
# @Time    : 2022/9/24
# @Author  : 大海
from abc import ABC

from rest_framework import serializers
from book.models import BookInfo


class BookInfoSerializer(serializers.Serializer):
    """图书数据序列化器"""
    name = serializers.CharField(max_length=20, label='名称')  # label DRF接口页面展示使用
    pub_date = serializers.DateField(label='发布日期', required=True)
    readcount = serializers.IntegerField(required=False, label='阅读量')
    commentcount = serializers.IntegerField(required=False, label='评论量')
    is_delete = serializers.BooleanField(required=False, label='逻辑删除')
    # hello = serializers.CharField()  # 增加模型中不存在字段


class HeroInfoSerializer(serializers.Serializer):
    """英雄数据序列化器"""
    GENDER_CHOICES = (
        (0, 'female'),
        (1, 'male')
    )
    id = serializers.IntegerField(label='ID', read_only=True)
    name = serializers.CharField(label='名字', max_length=20)
    gender = serializers.ChoiceField(choices=GENDER_CHOICES, label='性别', required=False)
    description = serializers.CharField(label='描述信息', max_length=200, required=False, allow_null=True)
    is_delete = serializers.BooleanField(label='是否删除', required=False)
    # 默认序列化外键id
    # book = serializers.PrimaryKeyRelatedField(label='书籍', read_only=True)
    # 序列化关联模型的__str__方法返回值序列化
    # book = serializers.StringRelatedField(label='书籍', read_only=True)
    # 关联模型序列化器所有字段序列化
    book = BookInfoSerializer()
    # book = serializers.PrimaryKeyRelatedField(label='书籍', queryset=BookInfo.objects.all())

#  book = serializers.PrimaryKeyRelatedField(label='书籍', read_only=True) 默认序列化外键id
In [1]: from book.models import BookInfo,PeopleInfo

In [2]: from book.serializers import BookInfoSerializer,HeroInfoSerializer

In [3]: hero = PeopleInfo.objects.get(id=1)

In [4]: serializer = HeroInfoSerializer(instance=hero)

In [5]: serializer.data
Out[5]: {'id': 1, 'name': '郭靖', 'gender': 1, 'description': '降龙十八掌', 'is_delete': False, 'book': 1}

# book = serializers.StringRelatedField(label='书籍', read_only=True) 序列化关联模型的__str__方法返回值序列化
In [1]: from book.serializers import BookInfoSerializer,HeroInfoSerializer
   ...: 
   ...: from book.models import BookInfo,PeopleInfo
   ...: 
   ...: hero = PeopleInfo.objects.get(id=1)
   ...: 
   ...: serializer = HeroInfoSerializer(instance=hero)

In [2]: serializer.data
Out[2]: {'id': 1, 'name': '郭靖', 'gender': 1, 'description': '降龙十八掌', 'is_delete': False, 'book': '射雕英雄传'}

# book = BookInfoSerializer()
In [1]: from book.serializers import BookInfoSerializer,HeroInfoSerializer
   ...: 
   ...: from book.models import BookInfo,PeopleInfo
   ...: 
   ...: hero = PeopleInfo.objects.get(id=1)
   ...: 
   ...: serializer = HeroInfoSerializer(instance=hero)

In [2]: serializer.data 关联模型序列化器所有字段序列化
Out[2]: {'id': 1, 'name': '郭靖', 'gender': 1, 'description': '降龙十八掌', 'is_delete': False, 'book': OrderedDict([('nam
e', '射雕英雄传'), ('pub_date', '1980-05-01'), ('readcount', 12), ('commentcount', 34), ('is_delete', False)])}

反序列使用

进入Django shell模式

: data = {
   ...:     'name': '北漂纪实',
   ...:     'pub_date':'2022-12-10'
   ...: }

In [2]: from book.serializers import BookInfoSerializer

In [3]: serializer = BookInfoSerializer(data=data)

In [4]: serializer.is_valid(raise_exception=True)  # 调用序列化器校验方法
Out[4]: True

In [5]: serializer.errors   # 获取错误信息
Out[5]: {}

In [6]: serializer.validated_data  # 获取反序列化后的数据
Out[6]: OrderedDict([('name', '北漂纪实'), ('pub_date', datetime.date(2022, 12, 10))])

单个字段校验

class BookInfoSerializer(serializers.Serializer):
    """图书数据序列化器"""
    name = serializers.CharField(max_length=20, label='名称')  # label DRF接口页面展示使用
    pub_date = serializers.DateField(label='发布日期', required=True)
    readcount = serializers.IntegerField(required=False, label='阅读量')
    commentcount = serializers.IntegerField(required=False, label='评论量')
    is_delete = serializers.BooleanField(required=False, label='逻辑删除')
    # hello = serializers.CharField()  # 增加模型中不存在字段
    peopleinfo_set = serializers.PrimaryKeyRelatedField(many=True, read_only=True)  # 序列化id
    # peopleinfo_set = HeroInfoSerializer(many=True)  # 一关联多 需要指定many=true 全部值

    def validate_name(self, value):
        """序列化器中单个字段校验"""
        if 'django' not in value.lower():
            raise serializers.ValidationError("图书不是关于Django的")
        return value

shell 模式

 from book.serializers import BookInfoSerializer

In [2]: data = {
   ...:     'name': '北漂纪实',
   ...:     'pub_date':'2022-12-10'
   ...: }

In [3]: serializer = BookInfoSerializer(data=data)
serializer.is_valid(raise_exception=True)
   ...: 
   ...: 
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
<ipython-input-5-c24be91bdde3> in <module>
----> 1 serializer.is_valid(raise_exception=True)
      2

D:\Python39\lib\site-packages\rest_framework\serializers.py in is_valid(self, raise_exception)
    233
    234         if self._errors and raise_exception:
--> 235             raise ValidationError(self.errors)
    236
    237         return not bool(self._errors)

ValidationError: {'name': [ErrorDetail(string='图书不是关于Django的', code='invalid')]}

serializers.py

class BookInfoSerializer(serializers.Serializer):
    """图书数据序列化器"""
    name = serializers.CharField(max_length=20, label='名称')  # label DRF接口页面展示使用
    pub_date = serializers.DateField(label='发布日期', required=True)
    readcount = serializers.IntegerField(required=False, label='阅读量')
    commentcount = serializers.IntegerField(required=False, label='评论量')
    is_delete = serializers.BooleanField(required=False, label='逻辑删除')
    # hello = serializers.CharField()  # 增加模型中不存在字段
    peopleinfo_set = serializers.PrimaryKeyRelatedField(many=True, read_only=True)  # 序列化id

    # peopleinfo_set = HeroInfoSerializer(many=True)  # 一关联多 需要指定many=true 全部值

    def validate_name(self, value):
        """序列化器中单个字段校验
        validate_<field_name>
        """
        if 'django' not in value.lower():
            raise serializers.ValidationError("图书不是关于Django的")
        return value

    def validate(self, attrs):
        """多个字段校验
        attrs 传过来的数据 字典类型
        """
        bread = attrs['readcount']
        bcomment = attrs['commentcount']
        if bread < bcomment:
            raise serializers.ValidationError('阅读量小于评论量')
        return attrs

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

    def update(self, instance, validated_data):
        """更新，instance为要更新的对象实例"""
        instance.name = validated_data.get('name', instance.name)
        instance.readcount = validated_data.get('readcount', instance.readcount)
        instance.commentcount = validated_data.get('commentcount', instance.commentcount)
        instance.save()
        return instance

修改

from book.serializers import BookInfoSerializer

In [4]: from book.models import BookInfo

In [5]: book = BookInfo.objects.get(id=5)

In [6]: data = {
   ...:     'name': '北漂纪实007-django',
   ...:     'pub_date':'2022-12-10',
   ...:     'readcount': 20,
   ...:     'commentcount':10
   ...: }

In [7]: serializer = BookInfoSerializer(book,data)

In [8]: serializer.is_valid(raise_exception=True)
Out[8]: True

In [9]: serializer.save()
Out[9]: <BookInfo: 北漂纪实007-django>

模型类序列化器ModelSerializer

模型序列化器

from rest_framework import serializers
from book.models import BookInfo


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

    class Meta:
        model = BookInfo  # 指定模型
        fields = '__all__'  # 指定序列化器包含所有字段

指定字段

使用fields来明确字段，__all__表名包含所有字段，也可以写明具体哪些字段，如

class BookInfoSerializer(serializers.ModelSerializer):
    """图书数据序列化器"""
    class Meta:
        model = BookInfo
        fields = ['id', 'name', 'bpub_date']

使用exclude可以明确排除掉哪些字段

class BookInfoSerializer(serializers.ModelSerializer):
    """图书数据序列化器"""
    class Meta:
        model = BookInfo
        exclude = ['readcount']

指明只读字段

class BookInfoSerializer(serializers.ModelSerializer):
    """图书数据序列化器"""
    class Meta:
        model = BookInfo
        fields = ('id', 'btitle', 'bpub_date'， 'bread', 'bcomment')
        read_only_fields = ('id', 'readcount')

修改选项参数

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