搭建环境

使用django-rest-framework中文文档——快速入门中的虚拟环境。
新建snippets应用程序

python .manage.py startapp snippets

注册相关应用程序，例如当前应用，rest_framework

创建数据库模型

编辑snippets/models.py文件

from django.db import models
from pygments.lexers import get_all_lexers
from pygments.styles import get_all_styles

LEXERS = [item for item in get_all_lexers() if item[1]]
LANGUAGE_CHOICES = sorted([(item[1][0], item[0]) for item in LEXERS])
STYLE_CHOICES = sorted([(item, item) for item in get_all_styles()])
"""
LEXERS 是一个大的list,每个元素都是元组，取出一个如下，可以看做 是各种语言 对应文件类型的标记。
[....,('Python 3', ('python3', 'py3'), (), ('text/x-python3', 'application/x-python3')),....]
LANGUAGE_CHOICES 我们对LEXERS，做了一些变型，去掉了一些无用的信息。
 [...,('python3', 'Python 3'),...]
STYLE_CHOICES 这个是样式选择
[..., ('monokai', 'monokai'), ...]

"""

class Snippet(models.Model):
    created = models.DateTimeField(auto_now_add=True)  #加入时间
    title = models.CharField(max_length=100, blank=True, default='')
    code = models.TextField()
    linenos = models.BooleanField(default=False)
    language = models.CharField(choices=LANGUAGE_CHOICES, default='python', max_length=100)
    style = models.CharField(choices=STYLE_CHOICES, default='friendly', max_length=100)

    class Meta:
        ordering = ['created']

数据库迁移

python manage.py makemigrations snippets
python manage.py migrate snippets

创建序列化器类

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):#创建数据
        """
        在给定已验证数据的情况下，创建并返回一个新的“代码段”实例。
        """
        return Snippet.objects.create(**validated_data)

    def update(self, instance, validated_data):   #更新数据
        """
        在给定已验证数据的情况下，更新并返回现有的“代码段”实例。
        instance 是要更新的实例对象
        validated_data 是要变更的数据，如果有的字段没有传，则使用instance对象原始的数据
        """
        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

序列化测试

python manage.py shell进入Django shell
执行以下语句，导入两条数据

>>> from rest_framework.parsers import JSONParser
>>> snippet = Snippet(code='foo = "bar"n')
>>> snippet.save()
>>> snippet = Snippet(code='print("hello, world")n')
>>> snippet.save()

序列化一个实例

>>> serializer = SnippetSerializer(snippet)
>>> serializer.data
{'id': 2, 'title': '', 'code': 'print("hello, world")n', 'linenos': False, 'language': 'python', 'style': 'friendly'}

此时，我们已将模型实例转换为 Python 原生数据类型。为了完成序列化过程，我们将数据渲染到json.

JSONRenderer().render(dict)将字典类型转换为字节流

>>> content = JSONRenderer().render(serializer.data)
>>> content
b'{"id":2,"title":"","code":"print(\"hello, world\")\n","linenos":false,"language":"python","style":"friendly"}'

反序列化也是类似的。首先我们将流解析为 Python 原生数据类型......

>>> import io
>>> stream = io.BytesIO(content)
>>> data = JSONParser().parse(stream)
>>> data
{'id': 2, 'title': '', 'code': 'print("hello, world")n', 'linenos': False, 'language': 'python', 'style': 'friendly'}

将字典存入模型中

>>> serializer = SnippetSerializer(data=data)
>>> serializer.is_valid()  #校验
True
>>> serializer.validated_data   #读取数据
OrderedDict([('title', ''), ('code', 'print("hello, world")'), ('linenos', False), ('language', 'python'), ('style', 'friendly')])
>>> serializer.save()  #存入数据
<Snippet: Snippet object (3)>

查询序列化集，而不是实例，加上many=True

>>> serializer = SnippetSerializer(Snippet.objects.all(), many=True)
>>> serializer.data
# [OrderedDict([('id', 1), ('title', ''), ('code', 'foo = "bar"n'), ('linenos', False), ('language', 'python'), ('style', 'friendly')]), OrderedDict([('id', 2), ('title', ''), ('code', 'print("hello, world")n'), ('linenos', False), ('language', 'python'), ('style', 'friendly')]), OrderedDict([('id', 3), ('title', ''), ('code', 'print("hello, world")'), ('linenos', False), ('language', 'python'), ('style', 'friendly')])]

使用 ModelSerializer

代替刚刚创建的 class SnippetSerializer(serializers.Serializer)
他们实现的效果一样，但是更加简化，并且ModelSerializer 默认实现了create和update

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

>>> from snippets.serializers import SnippetSerializer
>>> serializer = SnippetSerializer()
>>> print(repr(serializer))
SnippetSerializer():
    id = IntegerField(read_only=True)
    title = CharField(allow_blank=True, max_length=100, required=False)
    code = CharField(style={'base_template': 'textarea.html'})
    linenos = BooleanField(required=False)
    language = ChoiceField(choices=[('Clipper', 'FoxPro'),.......
    style = ChoiceField(choices=[('autumn', 'autumn'), .......

使用序列化编写视图

#snippets/views.py

```plaintext
from django.http import HttpResponse, JsonResponse
from django.views.decorators.csrf import csrf_exempt
from rest_framework.parsers import JSONParser
from snippets.models import Snippet
from snippets.serializers import SnippetSerializer


@csrf_exempt
def snippet_list(request):
    if request.method == 'GET':
        snippets = Snippet.objects.all()
        serializer = SnippetSerializer(snippets, many=True)
        return JsonResponse(serializer.data, safe=False)

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


@csrf_exempt
def snippet_detail(request, pk):
    """
    Retrieve, update or delete a 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)

创建snippets/urls.py文件：

from django.urls import path
from snippets import views

urlpatterns = [
    path('snippets/', views.snippet_list),
    path('snippets/<int:pk>/', views.snippet_detail),
]

修改tutorial/urls.py

from django.urls import path, include

urlpatterns = [
    path('', include('snippets.urls')),
]

http://127.0.0.1:8000/snippets/

http://127.0.0.1:8000/snippets/1

原文始发于微信公众号（小C学安全）：【Django进阶】django-rest-framework中文文档——序列化器