Django入门笔记3-Model 操作与 Serializer 序列化

在应用目录编写 Model.py 创建数据模型

"""
用户模块
"""

from django.db import models, transaction

class User(models.Model):

    """
    用户信息表
    """

    user_id = models.AutoField(primary_key=True, verbose_name='用户id')
    user_guid = models.CharField(max_length=150, verbose_name='用户guid')
    user_name = models.CharField(
        max_length=100, blank=True, null=True, verbose_name='用户名')
    real_name = models.CharField(
        max_length=50, blank=True, null=True, verbose_name='真实姓名')
    avatar = models.CharField(
        max_length=250, blank=True, null=True, verbose_name='头像')
    mobile = models.CharField(
        max_length=50, blank=True, null=True, verbose_name='手机')
    balance = models.DecimalField(
        max_digits=8, decimal_places=2, blank=True, null=True, verbose_name='账户余额')
    available_balance = models.DecimalField(
        max_digits=8, decimal_places=2, blank=True, null=True, verbose_name='可用金额')
    frozen_balance = models.DecimalField(
        max_digits=8, decimal_places=2, blank=True, null=True, verbose_name='冻结金额')
    all_balance = models.DecimalField(
        max_digits=8, decimal_places=2, blank=True, null=True, verbose_name='累计金额')
    wx_open_id = models.CharField(max_length=150, verbose_name='微信OpenID')
    wx_union_id = models.CharField(
        max_length=150, blank=True, null=True, verbose_name='微信UnionID')
    create_date = models.FloatField(blank=True, null=True, verbose_name='创建时间')
    last_login_date = models.FloatField(
        blank=True, null=True, verbose_name='最后登录时间')
    ip_address = models.CharField(
        max_length=50, blank=True, null=True, verbose_name='IP地址')
    gender = models.IntegerField(blank=True, null=True, verbose_name='性别')
    province = models.CharField(
        max_length=50, blank=True, null=True, verbose_name='省份')
    city = models.CharField(
        max_length=50, blank=True, null=True, verbose_name='城市')
    session_key = models.CharField(
        max_length=150, blank=True, null=True, verbose_name='会话秘钥')
    is_notify = models.IntegerField(blank=True, null=True, verbose_name='是否开启打卡通知')

    @classmethod
    def update_user_balance(cls, user_id, amount):

        # 手动让select for update和update语句发生在一个完整的事务里面
        with transaction.atomic():
            user = (
                cls.objects
                .select_for_update()
                .get(user_id=user_id)
            )
            user.available_balance += amount 
            user.balance = user.available_balance + user.frozen_balance
            if amount > 0:
                user.all_balance += amount
            user.save()
        return user

    class Meta:
        managed = False
        db_table = 'user'
        ordering = ['-create_date']
        verbose_name = '用户'
        verbose_name_plural = '用户'

我们还需要为我们的代码段模型创建初始迁移（initial migration），并首次同步数据库（migrate）。

python manage.py makemigrations 
python manage.py migrate

在应用目录新建Serializer.py 序列化模型

"""
用户模块
"""
from rest_framework import serializers
from apps.user.models import User
from apis.api_v1.enum import ErrorCode
from apis.api_v1.base import BaseApi

class GetUserSerializer(serializers.Serializer):
    """
    获取用户信息
    """
    token = serializers.CharField(max_length=150)
    user_id = serializers.IntegerField()
    def get_user(self, validated_data):
        result = dict()
        base_api = BaseApi()

        # 获取用户
        try:
            user = User.objects.get(user_id=validated_data["user_id"])
        except User.DoesNotExist:
            result["error_code"] = ErrorCode.用户不存在.value
            result["error"] = "用户不存在"
            return result
        
				# 认证
        if not base_api.authenticate_user(validated_data["token"], user.user_guid):
            result["error_code"] = ErrorCode.认证错误.value
            result["error"] = "认证错误"
            return result
        result["nick_name"] = user.user_name
        result["avatar"] = user.avatar
        result["error_code"] = ErrorCode.正确.value
        result["error"] = ""
        return result

serializer.py中属性类型与model.py 的属性类型一一对应

# model.py 
user_id = models.AutoField(primary_key=True, verbose_name='用户id')
#serializer.py
user_id = serializers.IntegerField()

create()和update()方法定义了在调用serializer.save()时如何创建和修改完整的实例。serializer.save()当实例存在时更新，不存在时创建

使用ModelSerializer 简化编写serializer

简化前

from rest_framework import serializers
from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES

class SnippetSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(required=False, allow_blank=True, max_length=100)
    code = serializers.CharField(style={'base_template': 'textarea.html'})
    linenos = serializers.BooleanField(required=False)
    language = serializers.ChoiceField(choices=LANGUAGE_CHOICES, default='python')
    style = serializers.ChoiceField(choices=STYLE_CHOICES, default='friendly')

    def create(self, validated_data):
        """
        根据提供的验证过的数据创建并返回一个新的`Snippet`实例。
        """
        return Snippet.objects.create(**validated_data)

    def update(self, instance, validated_data):
        """
        根据提供的验证过的数据更新和返回一个已经存在的`Snippet`实例。
        """
        instance.title = validated_data.get('title', instance.title)
        instance.code = validated_data.get('code', instance.code)
        instance.linenos = validated_data.get('linenos', instance.linenos)
        instance.language = validated_data.get('language', instance.language)
        instance.style = validated_data.get('style', instance.style)
        instance.save()
        return instance

简化后

class SnippetSerializer(serializers.ModelSerializer):
    class Meta:
        model = Snippet
        fields = ('id', 'title', 'code', 'linenos', 'language', 'style')

重要的是要记住，ModelSerializer类并不会做任何特别神奇的事情，它们只是创建序列化器类的快捷方式：

• 一组自动确定的字段。
• 默认简单实现的create()和update()方法。

应用目录编写view.py 编写Restful API

使用 Django view 编写 Restful API

def __init__(self, data, **kwargs):
        content = JSONRenderer().render(data)
        kwargs['content_type'] = 'application/json'
        super(JSONResponse, self).__init__(content, **kwargs)

@csrf_exempt
def snippet_detail(request, pk):
    """
    获取，更新或删除一个 code snippet。
    """
    try:
        snippet = Snippet.objects.get(pk=pk)
    except Snippet.DoesNotExist:
        return HttpResponse(status=404)

    if request.method == 'GET':
        serializer = SnippetSerializer(snippet)
        return JSONResponse(serializer.data)

    elif request.method == 'PUT':
        data = JSONParser().parse(request)
        serializer = SnippetSerializer(snippet, data=data)
        if serializer.is_valid():
            serializer.save()
            return JSONResponse(serializer.data)
        return JSONResponse(serializer.errors, status=400)

    elif request.method == 'DELETE':
        snippet.delete()
        return HttpResponse(status=204)

代码如上（部分非关键内容已省略）详情查看官方文档

1 - Serialization - Django REST framework中文站点

REST框架提供了两个可用于编写API视图的包装器（wrappers）。

1. 用于基于函数视图的@api_view装饰器。
2. 用于基于类视图的APIView类。

使用 Django Restful Framework view 重构 Restful API（函数视图）

通过一个函数中通过判断执行不同请求方法实现

@api_view(['GET', 'PUT', 'DELETE'])
def snippet_detail(request, pk):
    """
    获取，更新或删除一个snippet实例。
    """
    try:
        snippet = Snippet.objects.get(pk=pk)
    except Snippet.DoesNotExist:
        return Response(status=status.HTTP_404_NOT_FOUND)

    if request.method == 'GET':
        serializer = SnippetSerializer(snippet)
        return Response(serializer.data)

    elif request.method == 'PUT':
        serializer = SnippetSerializer(snippet, data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    elif request.method == 'DELETE':
        snippet.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)

使用 Django Restful Framework view 重构 Restful API （类视图CBV）

通过一个类中实现四种请求方法实现

class SnippetDetail(APIView):
    """
    检索，更新或删除一个snippet示例。
    """
    def get_object(self, pk):
        try:
            return Snippet.objects.get(pk=pk)
        except Snippet.DoesNotExist:
            raise Http404

    def get(self, request, pk, format=None):
        snippet = self.get_object(pk)
        serializer = SnippetSerializer(snippet)
        return Response(serializer.data)

    def put(self, request, pk, format=None):
        snippet = self.get_object(pk)
        serializer = SnippetSerializer(snippet, data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    def delete(self, request, pk, format=None):
        snippet = self.get_object(pk)
        snippet.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)

使用 mixins 通用的基于类的视图

使用 mixin 类可以更少的代码重构这些视图

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework import generics

class SnippetList(generics.ListCreateAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

class SnippetDetail(generics.RetrieveUpdateDestroyAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

详细内容参考文档

3 - Class based views - Django REST framework中文站点