序列化模块ModelSerializer

课程准备

配置：settings.py

INSTALLED_APPS = [
    # ...
    'rest_framework',
]

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'dg_proj',
        'USER': 'root',
        'PASSWORD': '',
    }
}
"""
任何__init__文件
import pymysql
pymysql.install_as_MySQLdb()
"""

LANGUAGE_CODE = 'zh-hans'
TIME_ZONE = 'Asia/Shanghai'
USE_I18N = True
USE_L10N = True
USE_TZ = False

MEDIA_URL = '/media/'
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')

路由

# 主
from django.conf.urls import url, include
from django.contrib import admin
from django.views.static import serve
from django.conf import settings
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^api/', include('api.urls')),
    url(r'^media/(?P<path>.*)', serve, {'document_root': settings.MEDIA_ROOT}),
]

# 子
from django.conf.urls import url
from . import views
urlpatterns = [

]

多表设计

"""
Book表：name、price、img、authors、publish、is_delete、create_time

Publish表：name、address、is_delete、create_time

Author表：name、age、is_delete、create_time

AuthorDetail表：mobile, author、is_delete、create_time

BaseModel基表
    is_delete、create_time
上面四表继承基表，可以继承两个字段
"""

基表

class BaseModel(models.Model):
    is_delete = models.BooleanField(default=False)
    create_time = models.DateTimeField(auto_now_add=True)

    # 设置 abstract = True 来声明基表，作为基表的Model不能在数据库中形成对应的表
    class Meta:
        abstract = True

提取每个表都有的字段，创建基类，其它表基础该基类

断关联多表关系

知识点（重点）

"""
1、外键位置：
    一对多 - 外键放多的一方
    一对一 - 从逻辑正反向考虑，如作者表与作者详情表，作者删除级联删除详情，详情删除作者依旧存在，所以建议外键在详情表中
    多对多 - 外键在关系表中

2、ORM正向方向连表查找：
    正向：通过外键字段 eg: author_detial_obj.author
    反向：通过related_name的值 eg：author_obj.detail
    注：依赖代码见下方

3、连表操作关系：
    1）作者删除，详情级联 - on_delete=models.CASCADE
    2）作者删除，详情置空 - null=True, on_delete=models.SET_NULL
    3）作者删除，详情重置 - default=0, on_delete=models.SET_DEFAULT
    4）作者删除，详情不动 - on_delete=models.DO_NOTHING
    注：拿作者与作者详情表举例
    db_constraint=False - 断关联

4、外键关联字段的参数 - 如何实现 断关联、目前表间操作关系、方向查询字段
    i）作者详情表中的
    author = models.OneToOneField(
        to='Author',
        related_name='detail',
        db_constraint=False,
        on_delete=models.CASCADE
    )

    ii）图书表中的
    publish = models.ForeignKey(
        to='Publish',
        related_name='books',
        db_constraint=False,
        on_delete=models.DO_NOTHING,
    )
    authors = models.ManyToManyField(
        to='Author'
        related_name='books',
        db_constraint=False,
    )
    注：ManyToManyField不能设置on_delete，OneToOneField、ForeignKey必须设置on_delete（django1.x系统默认级联，但是django2.x必须手动明确）
"""

model类

from django.db import models

# 图书管理系统：Book、Author、AuthorDetail、Publish
"""
Book表: name、price、img、authors、publish、is_delete、create_time
Publish表: name、address、is_delete、create_time
Author表: name、age、is_delete、create_time
AuthorDetail表: mobile, author、is_delete、create_time
"""

# 1) 基表
class BaseModel(models.Model):
    is_delete = models.BooleanField(default=False)
    create_time = models.DateTimeField(auto_now_add=True)

    # 作为基表的Model不能在数据库中形成对应的表，设置 abstract = True
    class Meta:
        abstract = True

class Book(BaseModel):
    """name、price、img、authors、publish、is_delete、create_time"""
    name = models.CharField(max_length=64)
    price = models.DecimalField(max_digits=5, decimal_places=2)
    img = models.ImageField(upload_to='img', default='img/default.jpg')
    publish = models.ForeignKey(
        to='Publish',
        db_constraint=False,  # 断关联
        related_name='books',  # 反向查询字段：publish_obj.books 就能访问所有出版的书
        on_delete=models.DO_NOTHING,  # 设置连表操作关系
    )
    authors = models.ManyToManyField(
        to='Author',
        db_constraint=False,
        related_name='books'
    )

    # 序列化插拔式属性 - 完成自定义字段名完成连表查询
    @property
    def publish_name(self):
        return self.publish.name

    @property
    def author_list(self):
        return self.authors.values('name', 'age', 'detail__mobile').all()

    class Meta:
        db_table = 'book'
        verbose_name = '书籍'
        verbose_name_plural = verbose_name
    def __str__(self):
        return self.name

class Publish(BaseModel):
    """name、address、is_delete、create_time"""
    name = models.CharField(max_length=64)
    address = models.CharField(max_length=64)

    class Meta:
        db_table = 'publish'
        verbose_name = '出版社'
        verbose_name_plural = verbose_name
    def __str__(self):
        return self.name

class Author(BaseModel):
    """name、age、is_delete、create_time"""
    name = models.CharField(max_length=64)
    age = models.IntegerField()

    class Meta:
        db_table = 'author'
        verbose_name = '作者'
        verbose_name_plural = verbose_name
    def __str__(self):
        return self.name

class AuthorDetail(BaseModel):
    """mobile, author、is_delete、create_time"""
    mobile = models.CharField(max_length=11)
    author = models.OneToOneField(
        to='Author',
        db_constraint=False,
        related_name='detail',
        on_delete=models.CASCADE,
    )

    class Meta:
        db_table = 'author_detail'
        verbose_name = '作者详情'
        verbose_name_plural = verbose_name
    def __str__(self):
        return '%s的详情' % self.author.name

序列化

序列化层：api/serializers.py

from rest_framework.serializers import ModelSerializer, SerializerMethodField
from rest_framework.exceptions import ValidationError
from . import models

# 可以单独作为Publish接口的序列化类，也可以作为Book序列化外键publish辅助的序列化组件
class PublishModelSerializer(ModelSerializer):
    class Meta:
        model = models.Publish
        fields = ('name', 'address')

class BookModelSerializer(ModelSerializer):
    # 了解: 该方式设置的序列化字段，必须在fields中声明
    # publish_address = SerializerMethodField()
    # def get_publish_address(self, obj):
    #     return obj.publish.address

    # 自定义连表深度 - 子序列化方式 - 该方式不能参与反序列化，使用在序列化反序列化共存时，不能书写
    publish = PublishModelSerializer()

    class Meta:
        # 序列化类关联的model类
        model = models.Book
        # 参与序列化的字段
        fields = ('name', 'price', 'img', 'author_list', 'publish')

        # 了解知识点
        # 所有字段
        # fields = '__all__'
        # 与fields不共存，exclude排除哪些字段
        # exclude = ('id', 'is_delete', 'create_time')
        # 自动连表深度
        # depth = 1

视图层：api/views.py

class Book(APIView):
    def get(self, request, *args, **kwargs):
        pk = kwargs.get('pk')
        if pk:
            try:
                book_obj = models.Book.objects.get(pk=pk, is_delete=False)
                book_data = serializers.BookModelSerializer(book_obj).data
            except:
                return Response({
                    'status': 1,
                    'msg': '书籍不存在'
                })
        else:
            book_query = models.Book.objects.filter(is_delete=False).all()
            book_data = serializers.BookModelSerializer(book_query, many=True).data
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': book_data
        })

路由层：api/urls.py

urlpatterns = [
    url(r'^books/$', views.Book.as_view()),
    url(r'^books/(?P<pk>.*)/$', views.Book.as_view()),
]

反序列化

序列化层：api/serializers.py

class BookModelDeserializer(ModelSerializer):
    class Meta:
        model = models.Book
        fields = ('name', 'price', 'publish', 'authors')
        # extra_kwargs 用来完成反序列化字段的 系统校验规则
        extra_kwargs = {
            'name': {
                'required': True,
                'min_length': 1,
                'error_messages': {
                    'required': '必填项',
                    'min_length': '太短',
                }
            }
        }

    # 局部钩子
    def validate_name(self, value):
        # 书名不能包含 g 字符
        if 'g' in value.lower():
            raise ValidationError('该g书不能出版')
        return value
    # 全局钩子
    def validate(self, attrs):
        publish = attrs.get('publish')
        name = attrs.get('name')
        if models.Book.objects.filter(name=name, publish=publish):
            raise ValidationError({'book': '该书已存在'})
        return attrs

    # ModelSerializer类已经帮我们实现了 create 与 update 方法

视图层：api/views.py

class Book(APIView):
    def post(self, request, *args, **kwargs):
        request_data = request.data
        book_ser = serializers.BookModelDeserializer(data=request_data)
        # raise_exception=True：当校验失败，马上终止当前视图方法，抛异常返回给前台
        book_ser.is_valid(raise_exception=True)
        book_obj = book_ser.save()
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': serializers.BookModelSerializer(book_obj).data
        })

路由层：api/urls.py

urlpatterns = [
    url(r'^books/$', views.Book.as_view()),
    url(r'^books/(?P<pk>.*)/$', views.Book.as_view()),
]

序列化与反序列化整合（重点）

序列化层：api/serializers.py

"""
1) fields中设置所有序列化与反序列化字段
2) extra_kwargs划分只序列化或只反序列化字段
    write_only：只反序列化
    read_only：只序列化
    自定义字段默认只序列化(read_only)
3) 设置反序列化所需的 系统、局部钩子、全局钩子 等校验规则
"""
class V2BookModelSerializer(ModelSerializer):
    class Meta:
        model = models.Book
        fields = ('name', 'price', 'img', 'author_list', 'publish_name', 'publish', 'authors')
        extra_kwargs = {
            'name': {
                'required': True,
                'min_length': 1,
                'error_messages': {
                    'required': '必填项',
                    'min_length': '太短',
                }
            },
            'publish': {
                'write_only': True  # 只参与反序列化字段
            },
            'authors': {
                'write_only': True
            },
            'img': {
                'read_only': True,  # 只参与序列化字段
            },
            'author_list': {
                'read_only': True,
            },
            'publish_name': {
                'read_only': True,
            }
        }

    def validate_name(self, value):
        # 书名不能包含 g 字符
        if 'g' in value.lower():
            raise ValidationError('该g书不能出版')
        return value

    def validate(self, attrs):
        publish = attrs.get('publish')
        name = attrs.get('name')
        if models.Book.objects.filter(name=name, publish=publish):
            raise ValidationError({'book': '该书已存在'})
        return attrs

视图层：api/views.py

class V2Book(APIView):
    # 单查：有pk
    # 群查：无pk
    def get(self, request, *args, **kwargs):
        pk = kwargs.get('pk')
        if pk:
            try:
                book_obj = models.Book.objects.get(pk=pk, is_delete=False)
                book_data = serializers.V2BookModelSerializer(book_obj).data
            except:
                return Response({
                    'status': 1,
                    'msg': '书籍不存在'
                })
        else:
            book_query = models.Book.objects.filter(is_delete=False).all()
            book_data = serializers.V2BookModelSerializer(book_query, many=True).data
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': book_data
        })

    # 单增：传的数据是与model对应的字典
    # 群增：传的数据是 装多个 model对应字典 的列表
    def post(self, request, *args, **kwargs):
        request_data = request.data
        if isinstance(request_data, dict):
            many = False
        elif isinstance(request_data, list):
            many = True
        else:
            return Response({
                'status': 1,
                'msg': '数据有误',
            })
        book_ser = serializers.V2BookModelSerializer(data=request_data, many=many)
        # 当校验失败，马上终止当前视图方法，抛异常返回给前台
        book_ser.is_valid(raise_exception=True)
        book_result = book_ser.save()
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': serializers.V2BookModelSerializer(book_result, many=many).data
        })

    # 单删：有pk
    # 群删：有pks   |  {"pks": [1, 2, 3]}
    def delete(self, request, *args, **kwargs):
        pk = kwargs.get('pk')
        if pk:
            pks = [pk]
        else:
            pks = request.data.get('pks')
        if models.Book.objects.filter(pk__in=pks, is_delete=False).update(is_delete=True):
            return Response({
                'status': 0,
                'msg': '删除成功',
            })
        return Response({
            'status': 1,
            'msg': '删除失败',
        })

路由层：api/urls.py

urlpatterns = [
    url(r'^v2/books/$', views.V2Book.as_view()),
    url(r'^v2/books/(?P<pk>.*)/$', views.V2Book.as_view()),
]