Django REST framework之序列化组件以及源码分析+全局、局部Hook

序列化两大功能

　　a.对queryset类型进行序列化

　　b.对用户请求的数据进行校验

a.对queryset类型进行序列化

举例说明：

表设计

from django.db import models


class UserGroup(models.Model):
    title = models.CharField(max_length=32)


class UserInfo(models.Model):
    user_type_choices = (
        (1, '普通用户'),
        (2, 'vip'),
        (3, 'svip'),
    )
    user_type = models.IntegerField(choices=user_type_choices)
    username = models.CharField(max_length=32, unique=True)
    password = models.CharField(max_length=64)
    group = models.ForeignKey('UserGroup', on_delete=models.CASCADE)
    roles = models.ManyToManyField('Role')


class UserToken(models.Model):
    user = models.OneToOneField(to='UserInfo', on_delete=models.CASCADE)
    token = models.CharField(max_length=64)


class Role(models.Model):
    title = models.CharField(max_length=32)

总路由：

from django.contrib import admin
from django.urls import path, re_path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    re_path('api/', include('api.urls')),
]

分发：

#!/usr/bin/env python
# -*- coding:utf-8 -*-

from django.urls import path, re_path, include
from api import views

urlpatterns = [

    # 序列化
    re_path('(?P<version>[v1|v2]+)/roles/$', views.RolesView.as_view()),
    re_path('(?P<version>[v1|v2]+)/userinfo/$', views.UserInfoView.as_view()),
    # 序列化并生成url查看详情restful返回链接
    re_path('(?P<version>[v1|v2]+)/group/(?P<pk>d+)$', views.GroupView.as_view(), name='group'),
    # 验证
    re_path('(?P<version>[v1|v2]+)/usergroup/$', views.UserGroupView.as_view()),

]

视图初探  继承serializers.Serializer   版本1  字段初探

import json
from django.shortcuts import render, HttpResponse
from rest_framework import serializers
from api import models


class RolesSerializer(serializers.Serializer):
    id = serializers.IntegerField()
    title = serializers.CharField()


class RolesView(APIView):

    def get(self, request, *args, **kwargs):
        # 方式1
        # roles = models.Role.objects.all().values('id', 'title')
        # roles = list(roles)
        # ret = json.dumps(roles, ensure_ascii=False)
        # 方式2
        # roles = models.Role.objects.all()
        # ser = RolesSerializer(instance=roles, many=True)
        # ret = json.dumps(ser.data, ensure_ascii=False)

        role = models.Role.objects.all().first()
        ser = RolesSerializer(instance=role, many=False)
        ret = json.dumps(ser.data, ensure_ascii=False)
        return HttpResponse(ret)

继承serializers.Serializer 版本2 进阶对序列类字段着手

class UserInfoSerializer(serializers.Serializer):
    # user_type = serializers.IntegerField()
    uuu = serializers.CharField(source='user_type')
    # 显示用户类型get_user_type_display内部是否callable若能直接调用，不能就直接返回
    ooo = serializers.CharField(source='get_user_type_display')
    username = serializers.CharField()
    password = serializers.CharField()
    # 显示用户组名称
    gp = serializers.CharField(source='group.title')
    # 显示用户在的所有组
    # roles = serializers.CharField(source='roles.all') # 力度不够
    # 处理ManyToManyField字段
    role = serializers.SerializerMethodField()
    
    def get_role(self, row):
        role_obj_list = row.roles.all()
        ret = []
        for item in role_obj_list:
            ret.append({'id': item.id, 'title': item.title})
        return ret

继承serializers.ModelSerializer 版本3 对字段着手

class UserInfoSerializer(serializers.ModelSerializer):
    ooo = serializers.CharField(source='get_user_type_display')
    # Serializer(BaseSerializer, metaclass=SerializerMetaclass)
    # ModelSerializer(Serializer)
    role = serializers.SerializerMethodField()

    class Meta:
        model = models.UserInfo
        # fields = '__all__'
        fields = ['id', 'username', 'password', 'ooo', 'role',  'group']

    def get_role(self, row):
        role_obj_list = row.roles.all()
        ret = []
        for item in role_obj_list:
            ret.append({'id': item.id, 'title': item.title})
        return ret

深度自动连表操作

class UserInfoSerializer(serializers.ModelSerializer):
    # ooo = serializers.CharField(source='get_user_type_display')
    # Serializer(BaseSerializer, metaclass=SerializerMetaclass)
    # ModelSerializer(Serializer)

    class Meta:
        model = models.UserInfo
        fields = '__all__'
        depth = 1  # 官方0~10 自我感觉最多2层，层数多响应数据慢

返回json数据中给用户提供链接字段

class UserInfoSerializer(serializers.ModelSerializer):
    # ooo = serializers.CharField(source='get_user_type_display')
    # Serializer(BaseSerializer, metaclass=SerializerMetaclass)
    # ModelSerializer(Serializer)
    # 生成url查看用户组详情链接restful规范在实例化时候必须加上context={'request': request}字段
    group = serializers.HyperlinkedIdentityField(view_name='group', lookup_field='group_id', lookup_url_kwarg='pk')

    class Meta:
        model = models.UserInfo
        fields = '__all__'
        depth = 1  # 官方0~10 自我感觉最多2层倒是行了


class UserInfoView(APIView):
    def get(self, request, *args, **kwargs):
        """
        取数据序列化
        :param request:
        :param args:
        :param kwargs:
        :return:
        """
        users = models.UserInfo.objects.all()
        ser = UserInfoSerializer(instance=users, many=True, context={'request': request})
        ret = json.dumps(ser.data, ensure_ascii=False)
        return HttpResponse(ret)

在页面显示提供url链接地址

class GroupSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.UserGroup
        fields = '__all__'


class GroupView(APIView):
    def get(self, request, *args, **kwargs):
        pk = kwargs.get('pk')
        obj = models.UserGroup.objects.filter(pk=pk).first()
        ser = GroupSerializer(instance=obj, many=False)
        return HttpResponse(json.dumps(ser.data, ensure_ascii=False))

b.对用户请求数据进行校验

自定义验证规则validators+钩子

class XValidator(object):
    def __init__(self, base):
        self.base = base

    def __call__(self, value):
        if not value.startswith(self.base):
            message = '必须以%s 开头' % self.base
            raise serializers.ValidationError(message)

    def set_context(self, serializer_field):
        """
        This hook is called by the serializer instance,
        prior to the validation call being made.
        """
        # 执行验证之前调用,serializer_fields是当前字段对象
        pass


class UserGroupSerializer(serializers.Serializer):
    title = serializers.CharField(error_messages={'required': '不能为空'}, validators=[XValidator('字母或者下划线'), ])
    # 局部钩子
    
    def validate_title(self, value):
        from rest_framework.exceptions import ValidationError
        print(value)
26         # raise ValidationError('仇恨有点大，不让你通过')
        return value
    # 全局钩子
    
    def validate(self, attrs):
        print(attrs)
        return attrs


class UserGroupView(APIView):
    def post(self, request, *args, **kwargs):
        ser = UserGroupSerializer(data=request.data)
        if ser.is_valid():
            print(ser.validated_data['title'])
        else:
            print(ser.errors)

        return HttpResponse('提交数据')

 序列化源码分析+钩子源码分析

 分析之前熟知继承关系：ModelSerializer--->Serializer--->BaseSerializer, metaclass=SerializerMetaclass

序列化分析：

        ModelSerializer--->Serializer--->BaseSerializer--->__new__(1.many=True,执行many_init生成ListSerializer对象；2many=False生成Serializer对象)---->序列化对象.data方法----->调父类super().data方法----->调用对象自己的self.to_representation对象（自己定义的序列化类里边没有，就走ModelSerializer里边找，里边也没有，在进一层Serializer）------------>Serializer类的(to_representation方法)---->for循环每个字段对象attribute = field.get_attribute(instance)--->返回get_attribute(instance, self.source_attrs)其中在这里instance就是queryset对象，self.source_attrs就是分割替换赋值等处理之后的source,当做参数传进去，判断是否可callable,是直接加括号执行，是数据属性就提取出来。

Hook函数：

局部钩子：is_valid--->self.run_validation(self.initial_data)---注意--->(serializer类的run_validation)--->to_internal_value(两个有序字典ret, errors)--->循环fiels--->钩子函数（字符串拼接，通过反射取出我们定义的钩子函数）抛错必须抛ValidationError

全局钩子：就在局部钩子下面在530行 返回attrs