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":"winxe6xa1x8cxe9x9dxa2xe8xbfx90xe7xbbxb42","desc":"winxe6xa1x8cxe9x9dxa2xe8xbfx90xe7xbbxb42","detail":"jabbokxe6x8ex88xe8xafxbe","learn_times":120,"degree":"middle","students":1,"fav_num":0,"click_num":0,"catalog":"xe8xbfx90xe7xbbxb4"}'
#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