Django REST framework ——序列化

朱雀 2023-06-16 10:51 12阅读 0赞

Django REST framework教程——序列化

# 创建项目 #

# python项目的虚拟环境 略
    
    # 安装我们所需的包
    pip install django
    pip install djangorestframework
    pip install pygments  # 高亮显示代码
    
    # 开始创建django项目
    django-admin startproject tutorial # project
    cd tutorial
    python manage.py startapp snippets # project-app
    
    # tutorial/settings.py 中 添加app
    INSTALLED_APPS = [
        ...
        'rest_framework',
        'snippets.apps.SnippetsConfig',
    ]

已经准备就绪，开始学习`序列化`

# 创建models #

`snippets/models.py`

from django.db import models
    from pygments.lexers import get_all_lexers
    from pygments.styles import get_all_styles
    
    # pygments 我们pip安装的，这里并不妨碍我们学习 序列化
    # 但有一些强迫症可能不会这里就看不下去，我们下面会简单说明一下。
    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)                                       # 创建时间
        title = models.CharField(max_length=100, blank=True, default='')                        # 文件名
        code = models.TextField()                                                               # 代码内容
        linenos = models.BooleanField(default=False)                                            # 行数
        language = models.CharField(choices=LANGUAGE_CHOICES, default='python', max_length=100) # 语言
        style = models.CharField(choices=STYLE_CHOICES, default='friendly', max_length=100)     # 风格
    
        class Meta:
            ordering = ['created']

我们还需要为代码片段模型创建初始迁移，并首次同步数据库。

python manage.py makemigrations snippets
    python manage.py migrate

好了，先停一停

看一下 `pygments`

# pygments
    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()])
    
    LEXERS 是一个大的list,每个元素都是元组，取出一个如下，可以看做 是各种语言 对应文件类型的标记。
    [....,('Python 3', ('python3', 'py3'), (), ('text/x-python3', 'application/x-python3')),....]
    
    LANGUAGE_CHOICES 我们对LEXERS，做了一些变型，去掉了一些无用的信息。
     [...,('python3', 'Python 3'),...]
        
    STYLE_CHOICES 这个是样式选择
    [..., ('monokai', 'monokai'), ...]

# 使用 **Serializer** #

在`snippets`目录名`serializers.py`并添加以下内容

from rest_framework import serializers
    from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES
    
    
    class SnippetSerializer(serializers.Serializer):
        id = serializers.IntegerField(read_only=True) # 只读
        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): # 创建
            """ Create and return a new `Snippet` instance, given the validated data. """
            return Snippet.objects.create(**validated_data)
    
        def update(self, instance, validated_data): # 更新
            """ Update and return an existing `Snippet` instance, given the validated data. instance 是要更新的实例对象 validated_data 是要变更的数据，如果有的字段没有传，则使用instance对象原始的数据 """
            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

# 序列化测试 #

(env) λ python manage.py shell
    Python 3.7.3 (default, Apr 24 2019, 15:29:51) [MSC v.1915 64 bit (AMD64)] on win32
    Type "help", "copyright", "credits" or "license" for more information.
    (InteractiveConsole)
    >>> 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()
    >>> serializer = SnippetSerializer(snippet)
    >>> serializer.data
    { 'id': 2, 'title': '', 'code': 'print("hello, world")\n', 'linenos': False, 'language': 'python', 'style': 'friendly'}
    >>> # 转成b
    >>> content = JSONRenderer().render(serializer.data)
    >>> content
    b'{"id":2,"title":"","code":"print(\\"hello, world\\")\\n","linenos":false,"language":"python","style":"friendly"}'
    
    >>> # b 转成 dict
    >>> import io
    >>> stream = io.BytesIO(content)
    >>> data = JSONParser().parse(stream)
    >>> data
    { 'id': 2, 'title': '', 'code': 'print("hello, world")\n', 'linenos': False, 'language': 'python', 'style': 'friendly'}
    
    # 将字典存入模型中
    >>> 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>
    
    
    # 查询序列化集，而不是实例，加上many=True
    >>> serializer = SnippetSerializer(Snippet.objects.all(), many=True)
    >>> serializer.data
    # [OrderedDict([('id', 1), ('title', ''), ('code', 'foo = "bar"\n'), ('linenos', False), ('language', 'python'), ('style', 'friendly')]), OrderedDict([('id', 2), ('title', ''), ('code', 'print("hello, world")\n'), ('linenos', False), ('language', 'python'), ('style', 'friendly')]), OrderedDict([('id', 3), ('title', ''), ('code', 'print("hello, world")'), ('linenos', False), ('language', 'python'), ('style', 'friendly')])]

# 使用 `ModelSerializer` #

# 代替刚刚创建的 class SnippetSerializer(serializers.Serializer)
    # 他们实现的效果一样，但是更加简化，并且`ModelSerializer` 默认实现了create和update
    class SnippetSerializer(serializers.ModelSerializer):
        class Meta:
            model = Snippet
            fields = ['id', 'title', 'code', 'linenos', 'language', 'style']
    
            
    # python manage.py shell
    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'),.......
    # style = ChoiceField(choices=[('autumn', 'autumn'), .......

`snippets/views.py`

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

@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)

`snippets/urls.py`

from django.urls import path
    from snippets import views
    
    urlpatterns = [
        path('snippets/', views.snippet_list),
        path('snippets/<int:pk>/', views.snippet_detail),
    ]

`tutorial/urls.py`

from django.urls import path, include
    
    urlpatterns = [
        path('', include('snippets.urls')),
    ]

# 测试http #

# 启动程序
    python manage.py runserver
    
    # 安装测试工具 命令行http客户端
    # https://blog.csdn.net/bobey/article/details/84863380 使用方法
    pip install httpie
    
    # 测试
    http http://127.0.0.1:8000/snippets/2/

系列教程  
[快速启动][Link 1]  
[1-序列化][1-]  
[2-请求与相应][2-]  
[3-基于类的views][3-_views]  
[4-身份验证和权限][4-]  
[5-关系和超链接API][5-_API]  
[6-视图和路由][6-]

[Link 1]: https://blog.csdn.net/sunt2018/article/details/103241355
[1-]: https://blog.csdn.net/sunt2018/article/details/103252879
[2-]: https://www.django-rest-framework.org/tutorial/2-requests-and-responses/#tutorial-2-requests-and-responses
[3-_views]: https://www.django-rest-framework.org/tutorial/3-class-based-views/
[4-]: https://www.django-rest-framework.org/tutorial/4-authentication-and-permissions/
[5-_API]: https://www.django-rest-framework.org/tutorial/5-relationships-and-hyperlinked-apis/
[6-]: https://www.django-rest-framework.org/tutorial/6-viewsets-and-routers/