DjangoRESTframework-请求与响应（Request Response）

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DjangoRESTframework——-请求与响应（Request and Response）

在这一章，我们将真正的开始接触REST framework的核心了。接下来介绍一下几个内建模块。

Request对象

REST framework提供了一个Request对象，它派生自HttpRequest，提供更多弹性的访问数据的序列化操作。它的核心是request.data属性，它类似于request.POST，在Web API中用处很大。

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request.POST #只能处理表单数据，只能在POST方法中起作用
request.data #可以处理任意的数据，能够在POST,PUT,PATCH方法中起作用

Response对象

REST framework提供了Response对象，他是一个TemplateResponse类型的对象，它能够提供未渲染的内容，使用合适的数据类型返回给客户端。

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return Response(data) #渲染数据给客户端

Status codes

使用数字状态的HTTP响应码，用于不必要的数据读取。它的使用需要非常注意，如果你给出了一个错误的状态码。REST framework为每个状态提供了更明确的状态码，比如HTTP_400_BAD_REQUEST

Wrapping API views

REST framework提供了两种wrapper，你可以用来编写API views

1.@api_view 装饰器，用于基于方法的视图

2.APIVIEW类，用于基于类的视图

这些装饰器提供了基本的方法能够确保你收到Request实例，为Reponse对象添加上下文。

这些装饰器也提供一些行为控制，比如返回405 Method Not Allowed在合适的情况下，也能够处理任何ParseError异常，当request.data是非法输入时。

把以上的内容拼起来复习一下，Pulling it all together

好了，现在我们可以使用这些新组件来编写view了。我们不需views.py中引入JSONResponse类，删掉它，继续coding。

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from rest_framework import status
from rest_framework.decorators import api_view
from rest_framework.response import Response
from snippets.models import Snippet
from snippets.serializers import SnippetSerializer

@api_view(['GET', 'POST'])
def snippet_list(request):
  if request.method == 'GET':
    snippet = Snippet.objects.all()
    serializer = SnippetSerializer(snippets, many=True)
    return Reponse(serializer.data)
  
  elif request.method == 'POST':
    serializer = SnippetSerializer(data=request.data)
    if serializer.is_valid():
      serializer.save()
      return Response(serializer.data, status=status.HTTP_201_CREATED)
    return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

现在的视图与之前相比，显得更加简洁了一些，看起来和Forms API看起来也非常相似。我们也使用了status codes，使我们返回的意义更加明确。下面是snippet的详细视图，对应的文件是views.py:

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@api_view(['GET', 'PUT', 'DELETE'])
def snippet_detail(request, pk):
    """
    Retrieve, update or delete a code snippet.
    """
    try:
        snippet = Snippet.objects.get(pk=pk)
    except Snippet.DoesNotExist:
        return Response(status=status.HTTP_404_NOT_FOUND)

    if request.method == 'GET':
        serializer = SnippetSerializer(snippet)
        return Response(serializer.data)

    elif request.method == 'PUT':
        serializer = SnippetSerializer(snippet, data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    elif request.method == 'DELETE':
        snippet.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)

这看起来就更加熟悉了，和一般的Django视图区别不大。

注意：我们不再明确的指定request和response中的内容类型，request.data能够帮我们处理传入的json格式的请求数据，但是它也能给处理其他类型的格式。类似地，我们能返回响应对象数据，允许REST framework用合适的数据类型渲染响应。

给我们的URLs添加可选的格式前缀

利用这一优点，我们的响应内容不再硬生生的绑定单一的内容格式，而可以支持格式前缀，定义我们需要返回的格式。比如http://example.com/api/items/4.sjon.

要达到这个目的的话，需要给添加一个format参数，就像这样：

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def snippet_list(request, format=None)
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def snippet_detail(request, pk, format=None)

现在需要更新urls.py,追加format_suffix_patterns

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from django.conf.urls import url
from rest_framework.urlpatterns import format_suffix_patterns
from snippets import views


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

urlpatterns = fromat_suffix_patterns(urlpatterns)

我们就不再需要添加其他额外的url策略，就能够给我们一个清晰，简洁的支持指定需要的响应格式。

应用跑起来是怎样的呢？

我们可以和之前一样列出所有的snippets

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PS E:\Study\Serializer_tutorial\tutorial> http http://127.0.0.1:8000/snippets/
HTTP/1.0 200 OK
Allow: POST, OPTIONS, GET
Content-Length: 319
Content-Type: application/json
Date: Tue, 10 Oct 2017 07:52:59 GMT
Server: WSGIServer/0.1 Python/2.7.13
Vary: Accept, Cookie
X-Frame-Options: SAMEORIGIN

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

我们也可以控制返回的格式，利用HTTP头或者格式前缀。

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PS E:\Study\Serializer_tutorial\tutorial> http http://127.0.0.1:8000/snippets/ Accept:application/json
HTTP/1.0 200 OK
Allow: POST, OPTIONS, GET
Content-Length: 319
Content-Type: application/json
Date: Tue, 10 Oct 2017 07:54:19 GMT
Server: WSGIServer/0.1 Python/2.7.13
Vary: Accept, Cookie
X-Frame-Options: SAMEORIGIN

[
    {
        "code": "foo = \"bar\"\n",
        "id": 1,
        "language": "python",
        "linenos": false,
        "style": "friendly",
        "title": ""
    },
    {
        "code": "print \"hello, world\n\"",
        "id": 2,
        "language": "python",
        "linenos": false,
        "style": "friendly",
        "title": ""
    },
    {
        "code": "print \"hello, world\n\"",
        "id": 3,
        "language": "python",
        "linenos": false,
        "style": "friendly",
        "title": ""
    }
]
PS E:\Study\Serializer_tutorial\tutorial> http http://127.0.0.1:8000/snippets/ Accept:text/html
HTTP/1.0 200 OK
Allow: POST, OPTIONS, GET
Content-Length: 7647
Content-Type: text/html; charset=utf-8
Date: Tue, 10 Oct 2017 07:54:50 GMT
Server: WSGIServer/0.1 Python/2.7.13
Vary: Accept, Cookie
X-Frame-Options: SAMEORIGIN

<!DOCTYPE html>
<html>
  <head>



        <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
        <meta name="robots" content="NONE,NOARCHIVE" />


      <title>Snippet List – Django REST framework</title>
PS E:\Study\Serializer_tutorial\tutorial> http http://127.0.0.1:8000/snippets.json
HTTP/1.0 200 OK
Allow: POST, OPTIONS, GET
Content-Length: 319
Content-Type: application/json
Date: Tue, 10 Oct 2017 07:55:25 GMT
Server: WSGIServer/0.1 Python/2.7.13
Vary: Accept, Cookie
X-Frame-Options: SAMEORIGIN

[
    {
        "code": "foo = \"bar\"\n",
        "id": 1,
        "language": "python",
        "linenos": false,
        "style": "friendly",
        "title": ""
    },
    {
        "code": "print \"hello, world\n\"",
PS E:\Study\Serializer_tutorial\tutorial> http http://127.0.0.1:8000/snippets.api
HTTP/1.0 200 OK
Allow: POST, OPTIONS, GET
Content-Length: 7668
Content-Type: text/html; charset=utf-8
Date: Tue, 10 Oct 2017 07:55:42 GMT
Server: WSGIServer/0.1 Python/2.7.13
Vary: Accept, Cookie
X-Frame-Options: SAMEORIGIN

<!DOCTYPE html>
<html>
  <head>



        <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
        <meta name="robots" content="NONE,NOARCHIVE" />


      <title>Snippet List – Django REST framework</title>


同时，我们可以控制请求数据的格式，利用Content-type头。

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PS E:\Study\Serializer_tutorial\tutorial> http --form POST http://127.0.0.1:8000/snippets/ code="print 123"
HTTP/1.0 201 Created
Allow: POST, OPTIONS, GET
Content-Length: 93
Content-Type: application/json
Date: Tue, 10 Oct 2017 07:58:55 GMT
Server: WSGIServer/0.1 Python/2.7.13
Vary: Accept, Cookie
X-Frame-Options: SAMEORIGIN

{
    "code": "print 123",
    "id": 4,
    "language": "python",
    "linenos": false,
    "style": "friendly",
    "title": ""
}

PS E:\Study\Serializer_tutorial\tutorial> http --json POST http://127.0.0.1:8000/snippets/ code="print 456"
HTTP/1.0 201 Created
Allow: POST, OPTIONS, GET
Content-Length: 93
Content-Type: application/json
Date: Tue, 10 Oct 2017 07:59:24 GMT
Server: WSGIServer/0.1 Python/2.7.13
Vary: Accept, Cookie
X-Frame-Options: SAMEORIGIN

{
    "code": "print 456",
    "id": 5,
    "language": "python",
    "linenos": false,
    "style": "friendly",
    "title": ""
}

可视化

由于API可以根据客户端的请求选择合适的响应类型。因此当接收到来自浏览器的请求时，会默认以html的格式响应请求。这可以让api能够返回，用于网页浏览。可视化之后，用浏览器开发和使用api将变得十分方便。所以现在用浏览器查看是这个画风：

image