DRF教程1-序列化

Serializers

Serializers 可以将queryset 和 model instance 转为为navite python datetype，然后render为JSON，给到api。也可以反序列化，把数据解析，验证数据，然后给到db。

django中的Serializer class，可以控制响应的输出方式。

序列化类

要建立web API，要做的第一件事就是对实例进行序列化，比如以json方式显示。我们可以生命序列化，它和django的forms很相似。在app目录下创建serializers.py

from rest_framework import serializers

from .models import Course

class CourseSerializer(serializers.Serializer):
    """
    Course序列化
    """
    id = serializers.IntegerField(read_only=True)
    name = serializers.CharField(required=True,max_length=64)
    desc = serializers.CharField(required=True,max_length=512)
    detail = serializers.CharField(required=True)
    learn_times = serializers.IntegerField(required=True)
    degree = serializers.ChoiceField(choices=(('hard','较难'),('middle','中级'),('easy','简单')), required=True)
    students = serializers.IntegerField(required=True)
    fav_num = serializers.IntegerField(required=True)
    click_num = serializers.IntegerField(required=True)
    catalog = serializers.CharField(required=True,max_length=32)
    # image = serializers.ImageField(required=True,max_length=64)
    # add_time = serializers.DateTimeField(required=True)

    def create(self, validated_data):
        """
        Create and return a new `Course` instance, given the validated data.
        """
        return Course.objects.create(**validated_data)

    def update(self, instance, validated_data):
        """
        Update and return an existing `Course` instance, given the validated data.
        """
        instance.name = validated_data.get('name', instance.name)
        instance.desc = validated_data.get('desc', instance.desc)
        instance.detail = validated_data.get('detail', instance.detail)
        instance.learn_times = validated_data.get('learn_times', instance.learn_times)
        instance.degree = validated_data.get('degree', instance.degree)
        instance.students = validated_data.get('students', instance.students)
        instance.fav_num = validated_data.get('fav_num', instance.fav_num)
        instance.click_num = validated_data.get('click_num', instance.click_num)
        instance.catalog = validated_data.get('catalog', instance.catalog)
        instance.save()
        return instance
#序列化类的第一部分，定义了序列化/反序列化的字段。creata和update方法定义了调用serializer.save()时如何创建或者修改实例
#

　　

使用序列化

from courses.models import Course
from courses.serializer import CourseSerializer
from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser

course = Course(name = "win桌面运维2",desc = "win桌面运维2", detail = "jabbok授课", learn_times = 120,degree = "middle", students = 1,fav_num = 0,click_num = 0,catalog = "运维")
course.save()
#使用Course类创建一个course实例，然后保存(调用序列化类中的create方法)
#这时这个字段已经在数据库中被创建，id字段自动出现

serializer = CourseSerializer(course)
serializer.data
{'id': 4, 'name': 'win桌面运维2', 'desc': 'win桌面运维2', 'detail': 'jabbok授课', 'learn_times': 120, 'degree': 'middle', 'students': 1, 'fav_num': 0, 'click_num': 0, 'catalog': '运维'}
#使用自定义的CourseSerializer序列化类，对course实例创建序列化实例serializer
#data属性显示序列化实例的数据

content = JSONRenderer().render(serializer.data)
content
b'{"id":4,"name":"win\xe6\xa1\x8c\xe9\x9d\xa2\xe8\xbf\x90\xe7\xbb\xb42","desc":"win\xe6\xa1\x8c\xe9\x9d\xa2\xe8\xbf\x90\xe7\xbb\xb42","detail":"jabbok\xe6\x8e\x88\xe8\xaf\xbe","learn_times":120,"degree":"middle","students":1,"fav_num":0,"click_num":0,"catalog":"\xe8\xbf\x90\xe7\xbb\xb4"}'
#在这时的数据还是python数据格式，最后一步把数据render为json数据。

import io

stream = io.BytesIO(content)
data = JSONParser().parse(stream)

serializer = CourseSerializer(data=data)
serializer.is_valid()
>>>True
serializer.validated_data
OrderedDict([('name', 'win桌面运维2'), ('desc', 'win桌面运维2'), ('detail', 'jabbok授课'), ('learn_times', 120), ('degree', 'middle'), ('students', 1), ('fav_num', 0), ('click_num', 0), ('catalog', '运维')])
serializer.save()
<Course: win桌面运维2>
#反序列化是相似的。先把一个steam解析为python数据格式
#然后把这个数据填充为一个实例对象。

serializer = CourseSerializer(Course.objects.all(), many=True)
serializer.data
[OrderedDict([('id', 1), ('name', 'django入门'), ('desc', 'dj入门'), ('detail', 'jabbok的课程'), ('learn_times', 120), ('degree', 'easy'), ('students', 12), ('fav_num', 0), ('click_num', 0), ('catalog', '运维')]), OrderedDict([('id', 2), ('name', '精通python'), ('desc', '精通python的课程'), ('detail', 'jabbok授课'), ('learn_times', 230), ('degree', 'easy'), ('students', 12), ('fav_num', 0), ('click_num', 0), ('catalog', '运维')]), OrderedDict([('id', 3), ('name', 'win桌面运维'), ('desc', 'win桌面运维'), ('detail', 'jabbok授课'), ('learn_times', 120), ('degree', 'middle'), ('students', 1), ('fav_num', 0), ('click_num', 0), ('catalog', '运维')]), OrderedDict([('id', 4), ('name', 'win桌面运维2'), ('desc', 'win桌面运维2'), ('detail', 'jabbok授课'), ('learn_times', 120), ('degree', 'middle'), ('students', 1), ('fav_num', 0), ('click_num', 0), ('catalog', '运维')]), OrderedDict([('id', 5), ('name', 'win桌面运维2'), ('desc', 'win桌面运维2'), ('detail', 'jabbok授课'), ('learn_times', 120), ('degree', 'middle'), ('students', 1), ('fav_num', 0), ('click_num', 0), ('catalog', '运维')])]
#我们也可以把一个查询集序列化，加入many=True即可。

　　

模型序列化

上面的序列化类和Course模型是高度相似的，django提供了ModelSerializer 类，可以对序列化类做简化，并且create和updata方法都默认在里面了。

class CourseSerializer(serializers.ModelSerializer):
    class Meta:
        model = Course
        fields = ('id', 'name', 'desc', 'detail', 'learn_times', 'degree','students','fav_num','click_num','catalog')

　　

class CourseSerializer(serializers.ModelSerializer):
    class Meta:
        model = Course
        fields = '__all__'
#如果序列化所以字段，就是要__all__

from courses.serializer import CourseSerializer
serializer = CourseSerializer()
print(repr(serializer))
CourseSerializer():
    id = IntegerField(label='ID', read_only=True)
    name = CharField(label='课程名称', max_length=64)
    desc = CharField(label='课程描述', max_length=512)
    detail = CharField(label='课程详情', style={'base_template': 'textarea.html'})
    learn_times = IntegerField(label='课程时长(分钟数)', max_value=2147483647, min_value=-2147483648, required=False)
    degree = ChoiceField(choices=(('hard', '较难'), ('middle', '中级'), ('easy', '简单')), label='课程难度')
    students = IntegerField(label='学习人数', max_value=2147483647, min_value=-2147483648, required=False)
    fav_num = IntegerField(label='收藏人数', max_value=2147483647, min_value=-2147483648, required=False)
    click_num = IntegerField(label='点击数', max_value=2147483647, min_value=-2147483648, required=False)
    catalog = CharField(label='课程类别', max_length=32)
#以上方法可以查看序列化类中包含的字段，可见，model中的字段都被继承过来了。

　　

重写.create() update()

使用django常规view提供web API

from django.http import HttpResponse, JsonResponse
from django.views.decorators.csrf import csrf_exempt
from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser

from .models import Course
from .serializer import CourseSerializer

@csrf_exempt
def course_list(request):
    """
    List all courses, or create a new course.
    """
    if request.method == 'GET':
        courses = Course.objects.all()
        serializer = CourseSerializer(courses, many=True)
        return JsonResponse(serializer.data, safe=False)

    elif request.method == 'POST':
        data = JSONParser().parse(request)
        serializer = CourseSerializer(data=data)
        if serializer.is_valid():
            serializer.save()
            return JsonResponse(serializer.data, status=201)
        return JsonResponse(serializer.errors, status=400)

@csrf_exempt
def course_detail(request, pk):
    """
    Retrieve, update or delete a code course.
    """
    try:
        course = Course.objects.get(pk=pk)
    except Course.DoesNotExist:
        return HttpResponse(status=404)

    if request.method == 'GET':
        serializer = CourseSerializer(course)
        return JsonResponse(serializer.data)

    elif request.method == 'PUT':
        data = JSONParser().parse(request)
        serializer = CourseSerializer(course, data=data)
        if serializer.is_valid():
            serializer.save()
            return JsonResponse(serializer.data)
        return JsonResponse(serializer.errors, status=400)

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

　　

urlpatterns = [
    path('admin/', xadmin.site.urls),
    path('course/', views.course_list,name='course_list'),
    path('course/<int:pk>/', views.course_detail,name='course_detail'),
]
#提供url

　　

http http://127.0.0.1:8008/course/
#列出所有courses，调用course_list视图

http http://127.0.0.1:8008/course/1/
#传入pk参数，调用course_detail视图

#这里使用python下的httpie工具