Django restful Framework 之序列化与反序列化

1. 首先在已建好的工程目录下新建app命名为snippets,并将snippets app以及rest_framework app加到工程目录的 INSTALLED_APPS 中去，具体如下：

INSTALLED_APPS = (
...
'rest_framework',
'snippets.apps.SnippetsConfig',
)

1.1构建自己的数据库表结构，代码如下：

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())

class Snippet(models.Model):
created = models.DateTimeField(auto_now_add=True)
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',)

生成表结构命令如下：

python manage.py makemigrations snippets
python manage.py migrate

1.2创建序列化类

为我们的web API提供一种针对建立models snippets 对象的序列化与反序列化的方式，并展示出来，比如json格式， 我们可以定义序列化类，和Django 中的forms比较相似的功能，接下来在

snippets目录下创建serializers.py， 具体如下：

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

def update(self, instance, validated_data):
"""
Update and return an existing `Snippet` instance, given the validated data.
"""
instance.title = validated_data.get('title', instance.title)
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

A serializer class is very similar to a Django

Form

class, and includes similar validation flags on the various fields, such as

required

,

max_length

and

default

.

The field flags can also control how the serializer should be displayed in certain circumstances, such as when rendering to HTML. The

{'base_template': 'textarea.html'}

flag above is equivalent to using

widget=widgets.Textarea

on a Django

Form

class. This is particularly useful for controlling how the browsable API should be displayed, as we'll see later in the tutorial.

We can actually also save ourselves some time by using the

ModelSerializer

class, as we'll see later, but for now we'll keep our serializer definition explicit.

接下来进入django的shell 环境，创建models实例，步骤如下：

from django.http import HttpResponse
from django.views.decorators.csrf import csrf_exempt
from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser
from snippets.models import Snippet
from snippets.serializers import SnippetSerializer

class JSONResponse(HttpResponse):
"""
An HttpResponse that renders its content into JSON.
"""
def __init__(self, data, **kwargs):
content = JSONRenderer().render(data)
kwargs['content_type'] = 'application/json'
super(JSONResponse, self).__init__(content, **kwargs)

@csrf_exempt
def snippet_list(request):
"""
List all code snippets, or create a new snippet.
"""
if request.method == 'GET':
snippets = Snippet.objects.all()
serializer = SnippetSerializer(snippets, many=True)
return JSONResponse(serializer.data)

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)

views.py

在app snippets中创建urls.py 具体如下：

from django.conf.urls import url
from snippets import views

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

在project 的url中定义总的路由对应关系，具体如下：

from django.conf.urls import url, include

urlpatterns = [
url(r'^/rest_api/', include('snippets.urls')),
]

接下来运行一下搭建好的demo，我们可以借助用python写的httpie测试，安装方式如下：

pip install httpie

测试方法如下：

localhost:cmdb JasonWang$ http http://127.0.0.1:8000/rest_api/snippets/ HTTP/1.0 200 OK
Content-Type: application/json
Date: Fri, 11 Nov 2016 08:24:52 GMT
Server: WSGIServer/0.2 CPython/3.5.0
X-Frame-Options: SAMEORIGIN

[
{
"code": "foo = \"Jason\"\n",
"id": 1,
"language": "python",
"linenos": false,
"style": "friendly",
"title": ""
},
{
"code": "print \"Hello,Jason\"\n",
"id": 2,
"language": "python",
"linenos": false,
"style": "friendly",
"title": ""
},
{
"code": "print \"Hello,Jason\"",
"id": 3,
"language": "python",
"linenos": false,
"style": "friendly",
"title": ""
}
]

通过下面的方式也可以测试具体snippet

localhost:cmdb JasonWang$ http http://127.0.0.1:8000/rest_api/snippets/2/ HTTP/1.0 200 OK
Content-Type: application/json
Date: Fri, 11 Nov 2016 08:28:32 GMT
Server: WSGIServer/0.2 CPython/3.5.0
X-Frame-Options: SAMEORIGIN

{
"code": "print \"Hello,Jason\"\n",
"id": 2,
"language": "python",
"linenos": false,
"style": "friendly",
"title": ""
}