Django-rest-framework (一)、序列化

朱雀 2022-05-28 04:45 233阅读 0赞

## 序列化 ##

django-rest-framework serializer可以很方便的实现model对象的序列化，对前端传递的数据进行验证等等，功能与django原生的form很相似，但是却比form更强大，下面体验一下。

## 开始 ##

安装：

pip install django-rest-framework

创建一个新django项目：

django-admin.py startproject rest
    python  manage.py startapp snippet

rest/settings.py添加app：

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

创建一个model  
snippet/models.py:

from django.db import models
    
    # Create your models here.
    LANGUAGE_CHOICES = (
        ('1', 'cn'),
        ('2', 'us')
    )
    
    STYLE_CHOICES = (
        ('1', 't1'),
        ('2', 't2')
    )
    
    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= '1',max_length=5)
        style = models.CharField(choices=STYLE_CHOICES, default='1',max_length=5)
    
        class Meta:
            ordering = ('created',)

创建serializer.py文件：  
snippet/serializer.py:

from rest_framework import serializers
    from snippet.models import Snippet,LANGUAGE_CHOICES,STYLE_CHOICES
    
    class Snippetserializer(serializers.Serializer):
        pk = serializers.IntegerField(read_only=True)
        title = serializers.CharField(required=False, allow_blank=True, max_length=32)
        code = serializers.CharField(style={
       'base_template': 'textarea.html'})
        linenos = serializers.BooleanField(required=False)
        language = serializers.ChoiceField(choices=LANGUAGE_CHOICES, default= '1')
        style = serializers.ChoiceField(choices=STYLE_CHOICES,  default='1')
    
        def create(self, validated_data):
            return Snippet.objects.create(**validated_data)
    
        def update(self, instance, 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

创建表结构：

python manage.py makemigrations
    python manage.py migrate

开始使用django命令行,写一些序列化测试代码：

$ python manage.py shell
    >>> from snippet.models import Snippet
    >>> from snippet.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()
    >>>> obj = Snippetserializer(snippet)
    >>> obj.data
    {'language': '1', 'pk': 2, 'title': '', 'code': 'print"hello,world"\n', 'linenos': False, 'style': '1'}
    >>> obj['code']
    <BoundField value=print"hello,world"
     errors=None>
    
    >>> content=JSONRenderer().render(obj.data)
    >>> stream = BytesIO(content)
    >>> content1 = JSONParser().parse(stream)
    >>> content2=JSONRenderer().render(obj.data).decode()
    >>> print(content)
    b'{
       "pk":2,"title":"","code":"print\\"hello,world\\"\\n","linenos":false,"language":"1","style":"1"}'
    >>> type(obj)
    <class 'snippet.serializers.Snippetserializer'>
    >>> type(obj.data)
    <class 'rest_framework.utils.serializer_helpers.ReturnDict'>
    >>> type(content)
    <class 'bytes'>
    >>> type(stream)
    <class '_io.BytesIO'>
    >>> content2=JSONRenderer().render(obj.data).decode()
    >>> type(content1)
    <class 'dict'>
    >>> type(content2)
    <class 'str'>
    >>> type(json.loads(content2))
    <class 'dict'>
    
    #可以看到，由rest serializer处理后的model对象变成了其的serializer对象，使用obj.data方法可以取出其内容，然后使用jsonrender方法将数据渲染成byte格式的json字符串，可以再通过bytesIO转换和通过jsonparser方法转换回dict格式。也可以直接在jsonrender的时候使用decode()方法处理，直接返回json格式str，然后通过json.loads()方法反序列化成dict格式。

**同时，作为为django量身定制的框架，serializer也支持queryset的序列化（原生json模块不支持序列化queryset），在序列化的时候添加一个many = True参数即可：**

>>> serializer= Snippetserializer(Snippet.objects.all(),many=True)
    >>> serializer.data
    [OrderedDict([('pk', 1), ('title', ''), ('code', 'foo="bar"\n'), ('linenos', False), ('language', '1'), ('style', '1')]), OrderedDict([('pk', 2), ('title', ''), ('code', 'print"hello,world"\n'), ('linenos', False), ('language', '1'), ('style', '1')])]
    >>> serializer.data[0]
    OrderedDict([('pk', 1), ('title', ''), ('code', 'foo="bar"\n'), ('linenos', False), ('language', '1'), ('style', '1')])
    >>> serializer.data[0]['code']
    'foo="bar"\n'

**梳理一下：**  
1.model对象通过serializer方法序列化成新的对象obj,obj.data可以取出此对象的各items  
2.jsonrender方法可以将obj.data渲染成byte格式对象，再通过byteIO处理可以转换成python的byte格式数据流。也可以decode成json风格str类型。  
3.jsonparser方法可以将数据流(json风格str)反处理成dict格式

## ModelSerializer ##

如modelform一样，restframework同样存在可以直接基于model关联，进行field字段关联验证等功能的模块，ModelSerializer.

改写snippet/serializer.py：

from rest_framework import serializers
    from snippet.models import Snippet
    
    class SnippetSerializer(serializers.ModelSerializer):
        class Meta:
            model = Snippet
            fields = ('id','title','code','linenos','language','style')

写一个视图views.py，提供list查询、提交，单个对象查询、修改、删除方法：

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 snippet.models import Snippet
    from snippet.serializers import SnippetSerializer
    
    
    
    class JSONResponse(HttpResponse):
    
        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):
    
        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)

定义urls规则关联视图函数：  
urls.py:

from django.conf.urls import url
    from django.contrib import admin
    from snippet import views as snippet_views
    
    urlpatterns = [
        url(r'^admin/', admin.site.urls),
        url(r'^snippets/$',snippet_views.snippet_list),
        url(r'^snippets/detail/(?P<pk>[0-9]+)/$', snippet_views.snippet_detail),
    ]

**验证测试：**  
开启服务：

python manage.py runserver

测试：

$ curl http://127.0.0.1:8000/snippets/
    [{
       "id":1,"title":"","code":"foo=\"bar\"\n","linenos":false,"language":"1","style":"1"},{
       "id":2,"title":"","code":"print\"hello,world\"\n","linenos":false,"language":"1","style":"1"}]ywq@ywq-ThinkPad-E470:/usr/local/myutils$ curl http://127.0.0.1:8000/snippets/detail/1
    $ curl http://127.0.0.1:8000/snippets/detail/1/
    {
       "id":1,"title":"","code":"foo=\"bar\"\n","linenos":false,"language":"1","style":"1"}

简单的接口OK了