Django框架深入了解_02(DRF之序列化、反序列化)

序列化：将Python对象准换成json格式的字符串，反之即为反序列化

DRF的序列化使用过程：

使用drf的序列化组件
-1 新建一个序列化类继承Serializer
-2 在类中写要序列化的字段

-在视图中使用序列化的类
-1 实例化序列化的类产生对象,在产生对象的时候，传入需要序列化的对象（queryset）
-2 对象.data
-3 return Response(对象.data)

使用示例：

新建Django项目：settings.py文件注册rest_framework，使用MySQL数据库创建数据

# settings.py
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'drf_ser01',
        'HOST': '127.0.0.1',
        'PORT': 3306,
        'USER': 'root',
        'PASSWORD': '123'
    }
}

# __init__.py
import pymysql
pymysql.install_as_MySQLdb()

from django.db import models

# Create your models here.


class Book(models.Model):
    title = models.CharField(max_length=32)
    price = models.DecimalField(decimal_places=1, max_digits=6)
    publish = models.ForeignKey(to='Publish')
    author = models.ManyToManyField(to='Author', through='Book2Author', through_fields=('book', 'author'))


class Publish(models.Model):
    name = models.CharField(max_length=32)
    addr = models.CharField(max_length=64, null=True)


class Author(models.Model):
    name = models.CharField(max_length=32)
    age = models.IntegerField()


class Book2Author(models.Model):
    book = models.ForeignKey(to='Book')
    author = models.ForeignKey(to='Author')

app01新建MySer.py

# 先创建一个BookSer序列化类
from rest_framework import serializers


class BookSer(serializers.Serializer):
    id = serializers.CharField()
    title = serializers.CharField()
    publish = serializers.CharField()
    author = serializers.CharField()

app01视图函数views.py中

from django.shortcuts import render,HttpResponse,redirect
from app01.MySer import BookSer
from rest_framework.response import Response
from rest_framework.views import APIView
from app01 import models

# Create your views here.

class Books(APIView):
    response = {'code': 100, 'msg': '查询成功'}
    def get(self, request):
        books = models.Book.objects.all()
        books_ser = BookSer(instance=books, many=True)
        return Response(books_ser.data)

配路由：

from django.conf.urls import url
from django.contrib import admin
from app01 import views


urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^books/', views.Books.as_view()),
]

（通过NaviCat创建图书数据，用于查询...）

使用Postman发送get请求，获取到数据库中所有图书信息

可以看出一对多和多对多的外键字段显示的是对象名字，下面进一步使用序列化，让信息显示更完善

-source：可以指定字段（name   publish.name），可以指定方法

-SerializerMethodField搭配方法使用（get_字段名字）                
publish_detail=serializers.SerializerMethodField(read_only=True)
def get_publish_detail(self,obj):
    return {'name':obj.publish.name,'city':obj.publish.city}

更新版本BookSer

from rest_framework import serializers


class BookSer(serializers.Serializer):
    id = serializers.CharField()
    title = serializers.CharField()
    publish = serializers.CharField(source='publish.name')
    author = serializers.SerializerMethodField()
    def get_author(self, obj):
        authors = []
        for author_obj in obj.author.all():
            authors.append({'name': author_obj.name, 'age': author_obj.age})
        return authors

 补充：

-read_only:反序列化时，不传
-write_only：序列化时，不显示

以上是序列化的一种方式

下面看看序列化的另外一种方式：ModelSerializers：指定了表模型

            class Meta:
                model=表模型
                #要显示的字段
                fields=('__all__')
                fields=('id','name')
                #要排除的字段
                exclude=('name')
                #深度控制
                depth=1
            -重写某个字段
                在Meta外部，重写某些字段，方式同Serializers

# 序列化方式二：
class BookSer(serializers.ModelSerializer):
    class Meta:
        model = models.Book
        fields = ('__all__')

如果只想取其中几个字段，可以进行指定：

# 序列化方式二：
class BookSer(serializers.ModelSerializer):
    class Meta:
        model = models.Book
        fields = ['id', 'title']
        # fields = ('__all__')

刚才看到__all__，序列化所有字段，查询到的数据里面publish和author都是对应id值，如果需要获取到对应publish和author的关联信息，可以在BookSer内，Meta外重新写字段，方式同serializers

# 序列化方式二：
class BookSer(serializers.ModelSerializer):
    class Meta:
        model = models.Book
        # fields = ['id', 'title']
        fields = ('__all__')
    publish = serializers.CharField(source='publish.name')
    author = serializers.SerializerMethodField()
    def get_author(self, obj):
        authors = []
        for author_obj in obj.author.all():
            authors.append({'name': author_obj.name, 'age': author_obj.age})
        return authors

改进：

class AuthorSer(serializers.Serializer):
    id = serializers.CharField()
    name = serializers.CharField()
    age = serializers.CharField()

# 序列化方式二改进：
class BookSer(serializers.ModelSerializer):
    class Meta:
        model = models.Book
        # fields = ['id', 'title']
        fields = ('__all__')
    publish = serializers.CharField(source='publish.name')
    author = serializers.SerializerMethodField()
    def get_author(self, obj):
        ret = AuthorSer(obj.author.all(), many=True)        
        return ret.data

 通过post请求新增数据：

对数据进行新增使用反序列化实现，这里反序列化有2种情况进行新增：

使用继承了Serializers序列化类的对象，反序列化(需重写create方法)

from django.db import models

# Create your models here.

class User(models.Model):
    name = models.CharField(max_length=32)
    password = models.CharField(max_length=64)
    choices = (('1', 'Super_Admin'), ('2', 'General_Admin'), ('3', 'General_User') )
    user_type = models.CharField(max_length=6, choices=choices, default='3')

class Book(models.Model):
    title = models.CharField(max_length=32)
    price = models.DecimalField(decimal_places=1, max_digits=6)
    publish = models.ForeignKey(to='Publish', null=True)
    author = models.ManyToManyField(to='Author')


class Publish(models.Model):
    name = models.CharField(max_length=32)
    addr = models.CharField(max_length=64, null=True)


class Author(models.Model):
    name = models.CharField(max_length=32)
    age = models.IntegerField()

class Book(APIView):
    def post(self, request):
        response = {'code': 100, 'msg': '新增成功'}
        # 使用继承了Serializers序列化类的对象，反序列化
        book = BookSer(data=request.data)
        if book.is_valid():
            # 清洗通过的数据,需要在MySer.py中重写create
            book.create(book.validated_data)
        return Response(response)

# MySer.py

class BookSer(serializers.Serializer):
    # read_only 反序列化的时候，该字段不传
    # 这里id可以不传自增，publish、author不传，当然需要在models里面把不传字段设置为null=True
    # author多对多字段不能设置null=True
    id = serializers.CharField(read_only=True) 
    title = serializers.CharField()
    price = serializers.CharField()
    publish = serializers.CharField(source='publish.id', read_only=True)
    author = serializers.SerializerMethodField(read_only=True)
    def get_author(self, obj):
        ret = AuthorSer(obj.author.all(), many=True)
        return ret.data
    # 重写create方法，才能在使用Serializer发序列化方法进行新增数据
    def create(self, validated_data):
        res = models.Book.objects.create(**validated_data)
        return res

使用继承了ModelSerializers序列化类的对象，反序列化

from django.db import models

# Create your models here.

class User(models.Model):
    name = models.CharField(max_length=32)
    password = models.CharField(max_length=64)
    choices = (('1', 'Super_Admin'), ('2', 'General_Admin'), ('3', 'General_User') )
    user_type = models.CharField(max_length=6, choices=choices, default='3')


class Book(models.Model):
    title = models.CharField(max_length=32)
    price = models.DecimalField(decimal_places=1, max_digits=6)
    publish = models.ForeignKey(to='Publish', null=True)
    author = models.ManyToManyField(to='Author')


class Publish(models.Model):
    name = models.CharField(max_length=32)
    addr = models.CharField(max_length=64, null=True)


class Author(models.Model):
    name = models.CharField(max_length=32)
    age = models.IntegerField()

class BookSer(serializers.ModelSerializer):
    class Meta:
        model = models.Book
        fields = "__all__"

class Book(APIView):

    def post(self, request):
        response = {'code': 100, 'msg': '新增成功'}

        # 使用继承了ModelSerializers序列化类的对象，反序列化
        book_ser = BookSer(data=request.data)
        if book_ser.is_valid():
            book_ser.save()
        else:
            response['error'] = book_ser.errors['name'][0]
        return Response(response)

 使用ModelSerializer反序列化save数据后，多对多关联的那张表也会自动关联产生新的数据。

局部校验和全局校验

# MySer.py

from rest_framework.exceptions import ValidationError
class BookSer(serializers.ModelSerializer):
    class Meta:
        model = models.Book
        fields = "__all__"

    def validate_title(self, value):
        if value.startswith('sb'):
            raise ValidationError('不能以sb开头')
        return value

    def validate(self, attrs):
        title = attrs.get('title')
        price = attrs.get('price')
        if title.startswith('禁书') or int(price) <= 15:
            raise ValidationError('书名或价格不正常')
        return attrs

 

总结：

-反序列化的校验
-validate_字段名(self,value):
-如果校验失败，抛出ValidationError（抛出的异常信息需要去bookser.errors中取）
-如果校验通过直接return value
-validate(self,attrs)
-attrs所有校验通过的数据，是个字典
-如果校验失败，抛出ValidationError
-如果校验通过直接return attrs