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virtualenv is a tool to create isolated Python environments.

建立一个新的环境

Before we do anything else we‘ll create a new virtual environment, using virtualenv. This will make sure our package configuration is kept nicely isolated from any other projects we‘re working on.

# 创建一个隔离的空间

virtualenv env
source env/bin/activate

Now that we‘re inside a virtualenv environment, we can install our package requirements.

# 安装所需模块

pip install django
pip install djangorestframework
pip install pygments  # We‘ll be using this for the code highlighting

Note: To exit the virtualenv environment at any time, just 键入deactivate. For more information see the virtualenv documentation.

入门

摘要:入门部分创建了一个Django项目。

Okay, we‘re ready to get coding. To get started, let‘s create a new project to work with.

# Linux下创建一个项目

cd ~
django-admin.py startproject tutorial
cd tutorial

[email protected]:~$ tree tutorial
tutorial
├── manage.py
└── tutorial
        ├── __init__.py
        ├── settings.py
        ├── urls.py
        └── wsgi.py

1 directory, 5 files

Once that‘s done we can create an app that we‘ll use to create a simple Web API.

# 创建一个app

python manage.py startapp snippets

We‘ll need to add our new snippets app and the rest_framework app to INSTALLED_APPS. Let‘s edit the tutorial/settings.py file:

# 配置文件

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

Please note that if you‘re using Django <1.9, you need to replace snippets.apps.SnippetsConfig with snippets.

Okay, we‘re ready to roll.

创建一个可以使用的model

For the purposes of this tutorial we‘re going to start by creating a simple Snippet model that is used to store code snippets. Go ahead and edit the snippets/models.py file. Note: Good programming practices include comments. Although you will find them in our repository version of this tutorial code, we have omitted them here to focus on the code itself.

# models.py

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‘,) #排序字段

We‘ll also need to create an initial migration for our snippet model, and sync the database for the first time.

# 初始化数据库

python manage.py makemigrations snippets
python manage.py migrate

创建一个Serializer类

The first thing we need to get started on our Web API is to provide a way of 序列化和反序列化 the snippet instances into representations such as json. We can do this by declaring serializers that work very similar to Django‘s forms. Create a file in the snippets directory named serializers.py and add the following.

#serializers.py

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

The first part of the serializer class defines the fields that get serialized/deserialized. The create() and update()methods define how fully fledged instances are created or modified when calling serializer.save()

A serializer class is very similar to a Django Form class, and includes similar validation flags on the various fields, such as requiredmax_length and default.

The field flags can also control how the serializer should be displayed in certain circumstances, such as when rendering to HTML. 上面的 {‘base_template‘: ‘textarea.html‘} flag 相当于 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.

实际上,我们也可以使用 the ModelSerializer class 来节省一些时间 , as we‘ll see later, but for now we‘ll keep our serializer definition explicit.

使用Serializers串行器

摘要:这一部分都是在python shell下操作的。

Before we go any further we‘ll familiarize ourselves with using our new Serializer class. Let‘s drop into the Django shell.

# python shell下

python manage.py shell

Okay, once we‘ve got a few imports out of the way, let‘s create a couple of code snippets to work with.

#

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‘)   #实例化一个对象并填写code字段,然后保存。
snippet.save()

snippet = Snippet(code=‘print "hello, world"\n‘)
snippet.save()

We‘ve now got a few snippet instances to play with. Let‘s take a look at serializing one of those instances.

# 

serializer = SnippetSerializer(snippet)   #snippet是类Snippet的对象
serializer.data # {‘id‘: 2, ‘title‘: u‘‘, ‘code‘: u‘print "hello, world"\n‘, ‘linenos‘: False, ‘language‘: u‘python‘, ‘style‘: u‘friendly‘}

At this point we‘ve translated the model instance into Python native datatypes. To finalize the serialization process we render the data into json.

#

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

反序列化是类似的. First we parse a stream into Python native datatypes...

#

from django.utils.six import BytesIO

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

...then we restore those native datatypes into a fully populated object instance.

#

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>

请注意,API与forms何其相似. 相似性甚至更加明显 when we start writing views that use our serializer.

我们也可以实例化 querysets 而不是 model instances. 为了做到这一点, 我们仅仅添加 a many=True flag to the serializer arguments.

#

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ModelSerializers

Our SnippetSerializer class is replicating a lot of information that‘s also contained in the Snippet model. 如果我们可以保持我们的代码更简洁,那将是很好的。

与Django提供Form类和ModelForm类的方式相同,REST框架包括Serializer类和ModelSerializer类。

让我们来看看使用ModelSerializer重构我们的serializer。再次打开文件 snippets/serializers.py , and replace the SnippetSerializer class with the following.

#

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

serializers 有一个很好的属性是你可以检查一个serializer instance的所有字段, by printing its representation. Open the Django shell with python manage.py shell, then try the following:

#

from snippets.serializers import SnippetSerializer
serializer = SnippetSerializer()
print(repr(serializer))
# SnippetSerializer():
#    id = IntegerField(label=‘ID‘, 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‘), (‘Cucumber‘, ‘Gherkin‘), (‘RobotFramework‘, ‘RobotFramework‘), (‘abap‘, ‘ABAP‘), (‘ada‘, ‘Ada‘)...
#    style = ChoiceField(choices=[(‘autumn‘, ‘autumn‘), (‘borland‘, ‘borland‘), (‘bw‘, ‘bw‘), (‘colorful‘, ‘colorful‘)...

Notes that ModelSerializer classes don‘t do anything particularly magical, they are simply a shortcut for creating serializer classes:

  • An automatically determined set of fields.
  • Simple default implementations for the create() and update() methods.

使用我们的Serializer编写正常的Django视图

让我们来看看该如何使用新的Serializer类来编写一些API视图。目前我们不会使用任何REST框架的其他功能,我们只编写一些常规的Django视图函数。

编辑 snippets/views.py文件,并添加以下内容。

#

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

The root of our API 将是一个视图,它支持列出所有现有的片段,或创建一个新的片段。

#

@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)

请注意,因为我们希望能够从不具有CSRF token的客户端以POST方法访问此视图函数,因此我们需要用csrf_exempt标记视图。这不是你通常想要做的事情,REST框架视图实际上使用比这更有明显的行为,但它现在将用于我们的目的。

我们还需要一个与 an individual snippet对应的视图,并可用于检索,更新或删除the snippet。

#

@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)

最后我们需要把这些视图函数连接起来。创建snippets/urls.py文件: 

#

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),
]

我们还需要在tutorial/urls.py文件中连接根urlconf ,以包含我们的片段应用程序的URL。

#

from django.conf.urls import url, include

urlpatterns = [
    url(r‘^‘, include(‘snippets.urls‘)),
]

It‘s worth noting that there are a couple of edge cases we‘re not dealing with properly at the moment. If we send malformed json, or if a request is made with a method that the view doesn‘t handle, then we‘ll end up with a 500 "server error" response. Still, this‘ll do for now.

测试我们在Web API上的第一次尝试

现在我们可以启动一个运行我们的代码片段的示例服务器。

退出shell...

quit()

...and start up Django‘s development server.

#

python manage.py runserver

Validating models...

0 errors found
Django version 1.11, using settings ‘tutorial.settings‘
Development server is running at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

在另一个终端窗口中,我们可以测试服务器。

我们可以使用curlhttpie来测试我们的API Httpie是用Python编写的用户友好的http客户端。我们来安装它。

您可以使用pip安装httpie:

#

pip install httpie

最后,我们可以得到所有片段的列表:

#

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"
  }
]

或者我们可以通过引用其id来获取特定的代码段:

#

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"
}

同样,您可以通过在网络浏览器中访问这些URL来显示相同??的json。



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