DRF框架-模型类序列化器ModelSerializer

如果我们想要使用序列化器对应的是Django的模型类，DRF为我们提供了ModelSerializer模型类序列化器来帮助我们快速创建一个Serializer类。

一、创建序列化器

class BookSerializer(serializers.ModelSerializer):
    # 图书数据序列化器
    # model 指明该序列化器处理的数据字段从模型类BookInfo参考生成
    # fields 指明该序列化器包含模型类中的哪些字段，'__all__'指明包含所有字段
   class Meta:
       model = BookInfo
       fields = '__all__'

class HeroSerializer(serializers.ModelSerializer):
    # 图书数据序列化器
    # model 指明该序列化器处理的数据字段从模型类HeroInfo参考生成
    # fields 指明该序列化器包含模型类中的哪些字段，'__all__'指明包含所有字段
    class Meta:
        model = HeroInfo
        fields = '__all__'

 1）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 ：

 fields = ('id', 'btitle', 'bpub_date')

2) 使用exclude可以明确排除掉哪些字段

 exclude = ('image',)

3) 默认ModelSerializer使用主键作为关联字段

>>> from booktest.serializers import HeroSerializer
>>> serializer = HeroSerializer()
>>> serializer
HeroSerializer():
    id = IntegerField(label='ID', read_only=True)
    hname = CharField(label='名称', max_length=20)
    hgender = ChoiceField(choices=((0, 'male'), (1, 'female')), label='性别', required=False, validators=[<django.core.validators.MinValueValidator object>, <django.core.validators.MaxValueValidator object>])
    hcomment = CharField(allow_null=True, label='描述信息', max_length=200, required=False)
    is_delete = BooleanField(label='逻辑删除', required=False)
    hbook = PrimaryKeyRelatedField(label='图书', queryset=BookInfo.objects.all())

但是我们可以使用depth来简单的生成嵌套表示，depth应该是整数，表明嵌套的层级数量。如：

class HeroInfoSerializer2(serializers.ModelSerializer):
    class Meta:
        model = HeroInfo
        fields = '__all__'
        depth = 1

测试结果如下：

>>> from booktest.serializers import HeroInfoSerializer2
>>> serializer = HeroInfoSerializer2()
>>> serializer
HeroInfoSerializer2():
    id = IntegerField(label='ID', read_only=True)
    hname = CharField(label='名称', max_length=20)
    hgender = ChoiceField(choices=((0, 'male'), (1, 'female')), label='性别', required=False, validators=[<django.core.validators.MinValueValidator object>, <django.core.validators.MaxValueValidator object>])
    hcomment = CharField(allow_null=True, label='描述信息', max_length=200, required=False)
    is_delete = BooleanField(label='逻辑删除', required=False)
    hbook = NestedSerializer(read_only=True):
        id = IntegerField(label='ID', read_only=True)
        btitle = CharField(label='名称', max_length=20)
        bpub_date = DateField(label='发布日期')
        bread = IntegerField(label='阅读量', max_value=2147483647, min_value=-2147483648, required=False)
        bcomment = IntegerField(label='评论量', max_value=2147483647, min_value=-2147483648, required=False)
        is_delete = BooleanField(label='逻辑删除', required=False)
        image = ImageField(allow_null=True, label='图片', max_length=100, required=False)

4) 显示指明字段，如：

class HeroSerializer3(serializers.ModelSerializer):
    hbook = BookSerializer()
    class Meta:
        model = HeroInfo
        fields = ('id','hname','hgender','hcomment','hbook')

测试结果：

>>> from booktest.serializers import HeroSerializer3
>>> from booktest.models import HeroInfo
>>> serializer = HeroSerializer3()
>>> serializer
HeroSerializer3():
    id = IntegerField(label='ID', read_only=True)
    hname = CharField(label='名称', max_length=20)
    hgender = ChoiceField(choices=((0, 'male'), (1, 'female')), label='性别', required=False, validators=[<django.core.validators.MinValueValidator object>, <django.core.validators.MaxValueValidator object>])
    hcomment = CharField(allow_null=True, label='描述信息', max_length=200, required=False)
    hbook = BookSerializer():
        id = IntegerField(label='ID', read_only=True)
        btitle = CharField(label='名称', max_length=20)
        bpub_date = DateField(label='发布日期')
        bread = IntegerField(label='阅读量', max_value=2147483647, min_value=-2147483648, required=False)
        bcomment = IntegerField(label='评论量', max_value=2147483647, min_value=-2147483648, required=False)
        is_delete = BooleanField(label='逻辑删除', required=False)
        image = ImageField(allow_null=True, label='图片', max_length=100, required=False)

5) 指明只读字段

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

class BookSerializer2(serializers.ModelSerializer):
    class Meta:
        model = BookInfo
        fields = ('id', 'btitle', 'bpub_date', 'bread', 'bcomment')
        read_only_fields = ('id', 'bread', 'bcomment')

二、查看序列化器

>>> from booktest.serializers import BookSerializer,HeroSerializer
>>> serializer = BookSerializer()
>>> serializer
BookSerializer():
    id = IntegerField(label='ID', read_only=True)
    btitle = CharField(label='名称', max_length=20)
    bpub_date = DateField(label='发布日期')
    bread = IntegerField(label='阅读量', max_value=2147483647, min_value=-2147483648, required=False)
    bcomment = IntegerField(label='评论量', max_value=2147483647, min_value=-2147483648, required=False)
    is_delete = BooleanField(label='逻辑删除', required=False)
    image = ImageField(allow_null=True, label='图片', max_length=100, required=False)
>>> serializer = HeroSerializer()
>>> serializer
HeroSerializer():
    id = IntegerField(label='ID', read_only=True)
    hname = CharField(label='名称', max_length=20)
    hgender = ChoiceField(choices=((0, 'male'), (1, 'female')), label='性别', required=False, 	validators=[<django.core.validators.MinValueValidator object>, 		<django.core.validators.MaxValueValidator object>])
    hcomment = CharField(allow_null=True, label='描述信息', max_length=200, required=False)
    is_delete = BooleanField(label='逻辑删除', required=False)
    hbook = PrimaryKeyRelatedField(label='图书', queryset=BookInfo.objects.all())

三、使用序列化器

ModelSerializer与常规的Serializer相同，但提供了：

• 基于模型类自动生成一系列字段

• 基于模型类自动为Serializer生成validators，比如unique_together

• 包含默认的create()和update()的实现

  如果创建序列化器对象的时候，没有传递instance实例，则调用save()方法的时候，create()被调用，相反，如果传递了instance实例，则调用save()方法的时候，update()被调用。

  下面以图书数据的序列化器演示序列化器的使用

  如下：添加数据库

  >>> from booktest.serializers import BookSerializer
  >>> from booktest.models import BookInfo
  >>> from datetime import date
  >>> data = {'btitle':'武则天传奇','bpub_date':date(1990,3,5)}
  >>> serializer = BookSerializer(data=data)   # 没有传递instance实例，新建数据
  >>> serializer.is_valid()
  True
  >>> serializer.save()

  如下：更新数据库

>>> from booktest.models import BookInfo
>>> from booktest.serializers import BookSerializer
>>> from datetime import date
>>> book = BookInfo.objects.get(id=9)   # 实例：instance
>>> book
<BookInfo: 三国演义（第二版）>
>>> data={'btitle':'三国演义<改编版>','bpub_date':date(1992,5,8)}
>>> serializer = BookSerializer(book,data=data)   # 传进了instance参数，表示更新数据库
>>> serializer.is_valid()
True
>>> serializer.save()
<BookInfo: 三国演义<改编版>>

四、添加额外参数

class BookSerializer(serializers.ModelSerializer):
    # 图书数据序列化器
    # model 指明该序列化器处理的数据字段从模型类BookInfo参考生成
    # fields 指明该序列化器包含模型类中的哪些字段，'__all__'指明包含所有字段
   class Meta:
       model = BookInfo
       fields = '__all__'
# 使用extra_kwargs参数为ModelSerializer添加或修改原有的选项参数
class BookSerializer3(serializers.ModelSerializer):
    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}
        }    
       

测试：

# 做对比：
>>> from booktest.serializers import BookSerializer,BookSerializer3
>>> ser = BookSerializer()
>>> ser
BookSerializer():
    id = IntegerField(label='ID', read_only=True)
    btitle = CharField(label='名称', max_length=20)
    bpub_date = DateField(label='发布日期')
    bread = IntegerField(label='阅读量', max_value=2147483647, min_value=-2147483648, required=False)
    bcomment = IntegerField(label='评论量', max_value=2147483647, min_value=-2147483648, required=False)
    is_delete = BooleanField(label='逻辑删除', required=False)
    image = ImageField(allow_null=True, label='图片', max_length=100, required=False)
    
# 测试添加参数的序列化器
>>> ser2 = BookSerializer3()
>>> ser2
BookSerializer3():
    id = IntegerField(label='ID', read_only=True)
    btitle = CharField(label='名称', max_length=20)
    bpub_date = DateField(label='发布日期')
    bread = IntegerField(label='阅读量', max_value=2147483647, min_value=0, required=True)
    bcomment = IntegerField(label='评论量', max_value=2147483647, min_value=0, required=True)