TEST framework（1）

1. 什么是REST

• REST从资源的角度类审视整个网络，它将分布在网络中某个节点的资源通过URL进行标识，客户端应用通过URL来获取资源的表征，获得这些表征致使这些应用转变状态
• REST与技术无关，代表的是一种软件架构风格，REST是Representational State Transfer的简称，中文翻译为“表征状态转移”
• 所有的数据，不过是通过网络获取的还是操作（增删改查）的数据，都是资源，将一切数据视为资源是REST区别与其他架构风格的最本质属性
• 对于REST这种面向资源的架构风格，有人提出一种全新的结构理念，即：面向资源架构（ROA：Resource Oriented Architecture）

2. 什么是 Django REST framework？

Django REST framework是一个基于Django开发的app，用于快速搭建REST API。

安装：

pip3 install djangorestframework

a. 快速使用

INSTALLED_APPS = [
    ...
    'rest_framework',
]

from rest_framework import routers
from . import views


router = routers.DefaultRouter()
router.register(r'users', views.UserInfoViewSet)

urlpatterns = [
    url(r'^', include(router.urls)),
]

from rest_framework import viewsets
from . import models
from . import serializers

# ########### 1. 基本处理方式 ###########

class UserInfoViewSet(viewsets.ModelViewSet):
    """
    API endpoint that allows users to be viewed or edited.
    """
    queryset = models.UserInfo.objects.all().order_by('-id')
    serializer_class = serializers.UserInfoSerializer

from rest_framework import serializers
from . import models

class UserInfoSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = models.UserInfo
        # fields = ('id', 'username', 'pwd','ug') # fields = '__all__'
        exclude = ('ug',)
        depth = 1  # 0<=depth<=10

PS：最终访问路径

[GET]          http://127.0.0.1:8000/api/users/
[POST]         http://127.0.0.1:8000/api/users/
[GET]          http://127.0.0.1:8000/api/users/7/
[PUT]          http://127.0.0.1:8000/api/users/7/
[DELETE]       http://127.0.0.1:8000/api/users/7/

b. 基于CBV

from django.conf.urls import url,include
from django.contrib import admin
from . import views

urlpatterns = [
    url(r'^users/$', views.UserList.as_view()),
    url(r'^users/(?P<pk>[0-9]+)/$', views.UserDetail.as_view()),
]

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.request import Request
from rest_framework.parsers import JSONParser
from . import models
from . import serializers


class UserList(APIView):
    def get(self, request, *args, **kwargs):
        user_list = models.UserInfo.objects.all()
        serializer = serializers.MySerializer(instance=user_list, many=True)
        return Response(serializer.data)

    def post(self, request, *args, **kwargs):
        data = JSONParser().parse(request)
        serializer = serializers.MySerializer(data=data)
        if serializer.is_valid():
            # print(serializer.data)
            # print(serializer.errors)
            # print(serializer.validated_data)
            # 如果有instance，则执行update方法；否则，执行create
            serializer.save()
            return Response(serializer.data, status=201)
        return Response(serializer.errors, status=400)


class UserDetail(APIView):
    def get(self, request, *args, **kwargs):
        obj = models.UserInfo.objects.filter(pk=kwargs.get('pk')).first()
        serializer = serializers.MySerializer(obj)
        return Response(serializer.data)

    def delete(self, request, *args, **kwargs):
        obj = models.UserInfo.objects.filter(pk=kwargs.get('pk')).first()
        obj.delete()
        return Response(status=204)

    def put(self, request, *args, **kwargs):
        data = JSONParser().parse(request)
        obj = models.UserInfo.objects.filter(pk=kwargs.get('pk')).first()
        serializer = serializers.MySerializer(obj, data=data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=400)

from rest_framework import serializers
from rest_framework.exceptions import ValidationError
from . import models


class MySerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    username = serializers.CharField(required=False, allow_blank=True, max_length=100)
    pwd = serializers.CharField()

    def validate_username(self, value):
        if value == '中国':
            raise ValidationError('用户名中存在敏感字符')
        return value

    def validate_pwd(self, value):
        print(value)
        return value

    def validate(self, attrs):
        print(attrs)
        return attrs

    def create(self, validated_data):
        """
        当执行save方法时，自动调用。instance未传值
        :param validated_data:
        :return:
        """
        print(validated_data)
        return models.UserInfo.objects.create(**validated_data)

    def update(self, instance, validated_data):
        """
        当执行save方法时，自动调用。instance传值
        :param instance:
        :param validated_data:
        :return:
        """
        instance.username = validated_data.get('username', instance.username)
        instance.save()
        return instance

c. 基于FBV

from django.conf.urls import url,include
from django.contrib import admin
from . import views

urlpatterns = [
    url(r'^users/$', views.user_list),
    url(r'^users/(?P<pk>[0-9]+)/$', views.user_detail),
]

from django.http import JsonResponse,HttpResponse
from rest_framework.response import Response
from rest_framework.parsers import JSONParser
from rest_framework.decorators import api_view
from .serializers import MySerializer
from . import models

@api_view(['GET',"POST"])
def user_list(request):
    """
    List all code snippets, or create a new snippet.
    """
    if request.method == 'GET':
        user_list = models.UserInfo.objects.all()
        serializer = MySerializer(user_list,many=True)
        return Response(serializer.data)

    elif request.method == 'POST':
        data = JSONParser().parse(request)
        serializer = MySerializer(data=data)
        if serializer.is_valid():
            print(serializer.data)
            print(serializer.errors)
            print(serializer.validated_data)
            # 如果有instance，则执行update方法；否则，执行create
            serializer.save()
            return Response(serializer.data, status=201)
        return Response(serializer.errors, status=400)

@api_view(['GET',"POST","PUT"])
def user_detail(request, pk):
    """
    Retrieve, update or delete a code snippet.
    """

    obj = models.UserInfo.objects.filter(pk=pk).first()
    if not obj:
        return HttpResponse(status=404)

    if request.method == 'GET':
        serializer = MySerializer(obj)
        # return JsonResponse(serializer.data,json_dumps_params={'ensure_ascii':False},content_type='application/json;charset=utf-8')
        return Response(serializer.data)

    elif request.method == 'PUT':
        data = JSONParser().parse(request)
        serializer = MySerializer(obj, data=data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=400)

    elif request.method == 'DELETE':
        obj.delete()
        return Response(status=204)

from rest_framework import serializers
from rest_framework.exceptions import ValidationError
from . import models


class MySerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    username = serializers.CharField(required=False, allow_blank=True, max_length=100)
    pwd = serializers.CharField()

    def validate_username(self, value):
        if value == '中国':
            raise ValidationError('用户名中存在敏感字符')
        return value

    def validate_pwd(self, value):
        print(value)
        return value

    def validate(self, attrs):
        print(attrs)
        return attrs

    def create(self, validated_data):
        """
        当执行save方法时，自动调用。instance未传值
        :param validated_data:
        :return:
        """
        print(validated_data)
        return models.UserInfo.objects.create(**validated_data)

    def update(self, instance, validated_data):
        """
        当执行save方法时，自动调用。instance传值
        :param instance:
        :param validated_data:
        :return:
        """
        instance.username = validated_data.get('username', instance.username)
        instance.save()
        return instance

 e.Serializers字段的参数

read_only=False,
 write_only=False,
 required=None, 
default=empty,
 initial=empty, 
source=None,
 label=None,
 help_text=None,
 style=None,
error_messages=None, 
validators=None,
 allow_null=False

3 有关rest framework 的几点技巧

ModelSerializer

1、ModelSerializer 比Serializer封装好了一层，直接自己生成的create和update，不用覆盖了，其实推荐用这个，毕竟Serializer封装的很低级，既然用django，就要用好点的。

正常的应该是这样的

class AccountSerializer(serializers.ModelSerializer):
    class Meta:
        model = Account
        fields = ('id', 'account_name', 'users', 'created')
class AccountSerializer(serializers.ModelSerializer):
    class Meta:
        model = Account
        fields = '__all__'

官网推荐用第一种，因为第二种，改变model时，可能无意会泄露数据

3、当一个model有外键的时候，默认显示的是外键的id，此时要显示外键的所有值可以用下面，depth，会把外键的所有值显示出来

class AccountSerializer(serializers.ModelSerializer):
    class Meta:
        model = Account
        fields = ('id', 'account_name', 'users', 'created')
        depth = 1

4、如果一个serializer中，要包含出了model以外的字段，可以

class AccountSerializer(serializers.ModelSerializer):
    url=serializers.CharField(source='get_absolute_url',
read_only=True)
    groups = serializers.PrimaryKeyRelatedField(many=True)

    class Meta:
        model = Account

外键关联信息的显示解决办法：
几种不同的RelatedField: StringRelatedField
                      PrimaryKeyRelatedField
                      HyperlinkedRelatedField
                      SlugRelatedField
                      HyperlinkIdentityField

不同的RelatedField ,显示的内容不同，详见官网http://www.django-rest-framework.org/api-guide/relations/

5、把一个字段变成只读字段，需要如下操作，自增字段默认是只读的，不显式表示也是可以的

class AccountSerializer(serializers.ModelSerializer):
    class Meta:
        model = Account
        fields = ('id', 'account_name', 'users', 'created')
        read_only_fields = ('account_name',)
user = serializers.PrimaryKeyRelatedField(read_only=True, default=serializers.CurrentUserDefault())

6、把某一个字段变为只读，然后存储，通过额外字段指定。

class CreateUserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ('email', 'username', 'password')
        extra_kwargs = {'password': {'write_only': True}}

    def create(self, validated_data):
        user = User(
            email=validated_data['email'],
            username=validated_data['username']
        )
        user.set_password(validated_data['password'])
        user.save()
        return user

7 嵌套关系的序列化方法

class TrackSerializer(serializers.ModelSerializer):
    class Meta:
        model = Track
        fields = ('order', 'title', 'duration')

class AlbumSerializer(serializers.ModelSerializer):
    tracks = TrackSerializer(many=True)

    class Meta:
        model = Album
        fields = ('album_name', 'artist', 'tracks')

    def create(self, validated_data):
        tracks_data = validated_data.pop('tracks')
        album = Album.objects.create(**validated_data)
        for track_data in tracks_data:
            Track.objects.create(album=album, **track_data)
        return album