django rest-farme-work 的使用(2)
serialization (序列化)
本測試項目例子地址為:
tomchristie/rest-framework-tutorial
開始構建一個新的程序
創建一個新的環境
virtualenv env
source env/bin/activate
安裝相應的包
pip install django
pip install djangorestframework
pip install pygments # We‘ll be using this for the code highlighting(代碼高亮)
創建一個項目
cd ~ django-admin.py startproject tutorial cd tutorial
建立一個App
python manage.py startapp snippets
在settings 文件中添加下配置
```INSTALLED_APPS = (
‘rest_framework‘,
‘snippets.apps.SnippetsConfig‘,
```
在 snippets/models.py 中添加
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‘,)
我們還需要為我們的片段模型創建初始遷移,並首次同步數據庫。
python manage.py makemigrations snippets
python manage.py migrate
創建一個序列化類
我們需要開始使用Web API的第一件事就是提供一種將代碼片段實例序列化和反序列化為表示形式的方法json。我們可以通過聲明與Django的表單非常相似的序列化器來實現這一點。在snippets名為的目錄中創建一個文件serializers.py並添加以下內容。
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
序列化器類的第一部分定義了序列化/反序列化的字段。該create()和update()方法定義實例如何完全成熟的創建或修改時調用serializer.save()
甲串行類非常類似於一個Django Form類,並且包括關於各個字段類似的驗證標記,如required,max_length和default。
字段標誌還可以控制在某些情況下應該如何顯示序列化程序,例如在呈現為HTML時。{‘base_template‘: ‘textarea.html‘}上面的標誌等同於widget=widgets.Textarea在Django Form類上使用。這對於控制如何顯示可瀏覽的API特別有用,正如我們將在本教程後面看到的。
我們實際上也可以通過使用這個ModelSerializer類節省一些時間,我們稍後會看到,但現在我們將保持我們的序列化器定義清晰。
測試序列化類
在我們繼續之前,我們將熟悉使用我們的新Serializer類。我們來看看Django shell。
from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser
snippet = Snippet(code=‘foo = "bar"\n‘)
snippet.save()
snippet = Snippet(code=‘print "hello, world"\n‘)
snippet.save()
我們來看看序列化其中的一個實例。
serializer = SnippetSerializer(snippet)
serializer.data
# {‘id‘: 2, ‘title‘: u‘‘, ‘code‘: u‘print "hello, world"\n‘, ‘linenos‘: False, ‘language‘: u‘python‘, ‘style‘: u‘friendly‘}
在前面上,我們已經將模型實例轉換為Python本地數據類型。為了完成序列化過程,我們將數據渲染到json
content = JSONRenderer().render(serializer.data)
content
# ‘{"id": 2, "title": "", "code": "print \\"hello, world\\"\\n", "linenos": false, "language": "python", "style": "friendly"}‘
反序列化
from django.utils.six import BytesIO
stream = BytesIO(content)
data = JSONParser().parse(stream)
將本地的數據類型恢復填充到數據庫
serializer = SnippetSerializer(data=data)
serializer.is_valid()
# True
serializer.validated_data
# OrderedDict([(‘title‘, ‘‘), (‘code‘, ‘print "hello, world"\n‘), (‘linenos‘, False), (‘language‘, ‘python‘), (‘style‘, ‘friendly‘)])
serializer.save()
# <Snippet: Snippet object>
註意API與表單的工作方式相似。當我們開始編寫使用我們的序列化器的視圖時,相似性應該變得更加明顯。
我們也可以序列化查詢集而不是模型實例。為此,我們只需many=True在序列化參數中添加一個標誌即可
serializer = SnippetSerializer(Snippet.objects.all(), many=True)
serializer.data
# [OrderedDict([(‘id‘, 1), (‘title‘, u‘‘), (‘code‘, u‘foo = "bar"\n‘), (‘linenos‘, False), (‘language‘, ‘python‘), (‘style‘, ‘friendly‘)]), OrderedDict([(‘id‘, 2), (‘title‘, u‘‘), (‘code‘, u‘print "hello, world"\n‘), (‘linenos‘, False), (‘language‘, ‘python‘), (‘style‘, ‘friendly‘)]), OrderedDict([(‘id‘, 3), (‘title‘, u‘‘), (‘code‘, u‘print "hello, world"‘), (‘linenos‘, False), (‘language‘, ‘python‘), (‘style‘, ‘friendly‘)])]
使用ModelSerializer
前面我們SnippetSerializer類復制Snippet模型中包含的大量信息。如果我們可以保持我們的代碼更加簡潔。
讓我們看看使用ModelSerializer類重構我們的序列化程序。snippets/serializers.py再次打開文件,把SnippetSerializer類重新定義,如下
class SnippetSerializer(serializers.ModelSerializer):
class Meta:
model = Snippet
fields = (‘id‘, ‘title‘, ‘code‘, ‘linenos‘, ‘language‘, ‘style‘)
記住ModelSerializer類不要做任何特別的事情是很重要的,它們只是創建序列化類的一個捷徑。
- 自動確定的一組字段。
- 簡單的默認實現create()和update()方法。
使用我們的序列化程序編寫常規的Django視圖
編輯snippets/views.py文件,並添加以下內容。
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 snippets.models import Snippet
from snippets.serializers import SnippetSerializer
##ddvim
@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, 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)
配置url
from django.conf.urls import url, include
from snippets import views
# Additionally, we include login URLs for the browsable API.
urlpatterns = [
url(r‘^snippets/$‘,views.snippet_list),
url(r‘^snippets/(?P<pk>[0-9]+)/$‘,views.snippet_detail),
]
安裝調試工具
pip install httpie
測試
http http://127.0.0.1:8000/snippets/
HTTP/1.1 200 OK
...
[
{
"id": 1,
"title": "",
"code": "foo = \"bar\"\n",
"linenos": false,
"language": "python",
"style": "friendly"
},
{
"id": 2,
"title": "",
"code": "print \"hello, world\"\n",
"linenos": false,
"language": "python",
"style": "friendly"
}
]
http http://127.0.0.1:8000/snippets/2/
HTTP/1.1 200 OK
...
{
"id": 2,
"title": "",
"code": "print \"hello, world\"\n",
"linenos": false,
"language": "python",
"style": "friendly"
}
django rest-farme-work 的使用(2)