01_Tutorial 1: Serialization 序列化

1、序列化

1、官方教程

https://q1mi.github.io/Django-REST-framework-documentation/tutorial/1-serialization_zh/

https://www.django-rest-framework.org/tutorial/1-serialization/

2、序列化方式1：serializers.Serializer

# 序列化方式1：serializers.Serializer

# 序列化方式1：serializers.Serializer

class SnippetSerializer1(serializers.Serializer):
    """序列化，正反"""
    """
    序列化字段  GET请求
    """
    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'})
    # 多文本框的类型，比如XML，HTML，SHELL, python
    # 在某些情况下如何显示，比如渲染HTML的时候
    # {'base_template': 'textarea.html'}标志等同于在Django Form类中使用widget=widgets.Textarea

    linenos = serializers.BooleanField(required=True)
    language = serializers.ChoiceField(choices=LANGUAGE_CHOICES, default='python')
    style = serializers.ChoiceField(choices=STYLE_CHOICES, default='friendly')

    """
    反序列化字段  POST,PUT请求
    """

    def create(self, validated_data):
        """
        根据提供的验证过的数据，创建并返回一个新的snippet实例
        """
        return Snippet.objects.create(**validated_data)  # 保存到数据库

    def update(self, instance, validated_data):
        """
        根据提供的验证过的数据更新和返回一个已经存在的`Snippet`实例。
        """
        instance.title = validated_data.get('title', instance.title)  # 如果post该字段则取该字段，否则直接从instance中取
        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()  # 保存到db
        return instance

3、view视图

from django.test import TestCase

# Create your tests here.


from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser


# ## 序列化  GET方法
def test1():
    snippet = Snippet(code='foo = "bar"
')
    snippet.save()

    snippet = Snippet(code='print "hello world"
')  # 获取字段，其他的都default
    snippet.save()  # 保存到db
    serializer = SnippetSerializer(snippet)  # 序列化为一个class对象
    serializer.data
    # {'id': 2, 'title': '', 'code': 'print "hello world"
', 'linenos': False, 'language': 'python', 'style': 'friendly'}
    type(serializer.data)  # 现在是什么类型呢？  ReturnDict
    # <class 'rest_framework.utils.serializer_helpers.ReturnDict'>

    content = JSONRenderer().render(serializer.data)  # 转化为json, Python原生数据类型
    # content
    # b'{"id":2,"title":"","code":"print \"hello world\"\n","linenos":false,"language":"python","style":"friendly"}'
    type(content)
    # <class 'bytes'>


# ## 反序列化 POST PUT
def test2(content):
    from django.utils.six import BytesIO  # IO,内存的数据

    stream = BytesIO(content)  # 获取内存中的数据    # <_io.BytesIO object at 0x00000264CC1FE780>
    data = JSONParser().parse(stream)  # 解析为data，什么类型？  一个流（stream）解析为Python原生数据类型
    type(data)  # <class 'dict'>

    serializer = SnippetSerializer(data=data)  # 序列化
    serializer.is_valid()  # 校验
    # True
    serializer.validated_data  # 校验通过的数据
    # OrderedDict([('title', ''), ('code', 'print "hello world"'),('linenos', False), ('language', 'python'), ('style', 'friendly')])
    type(serializer.validated_data)
    # <class 'collections.OrderedDict'>

    serializer.save()  # 保存到db，什么类型？   将Python原生数据类型恢复成正常的对象实例
    # <Snippet: Snippet object (3)>

总结

# ## 总结
'''
POST方法create   
反序列化      Python原生数据类型 --->  模型实例

1、json类型的数据，每个字段必须存在    
b'{"id":2,"title":"","code":"print \"hello world\"\n","linenos":false,"language":"python","style":"friendly"}'

2、解析成为dict字典，<class 'dict'>                             Python原生数据类型
data = JSONParser().parse(stream)

3、序列化，<class 'snippets.serializers.SnippetSerializer'>
serializer = SnippetSerializer(data=data)

4、是否校验通过
serializer.is_valid()

5、校验后的数据， <class 'collections.OrderedDict'>
serializer.validated_data

6、保存到DB，<Snippet: Snippet object (3)>                       正常的对象实例
serializer.save()

'''


'''
GET list方法总结  
序列化   模型实例 --->   Python原生数据类型

1、接收每个字段，snippet = Snippet(code='foo = "bar"
')
code='foo = "bar"
', title='', style='friendly',language='python', linenos=False

2、保存到DB   <class 'snippets.models.Snippet'>
snippet.save()

3、序列化，对象                                                    模型实例
serializer = SnippetSerializer(snippet)         

4、序列化的数据    # <class 'rest_framework.utils.serializer_helpers.ReturnDict'>
serializer.data

5、转换为json数据   <class 'bytes'>                               Python原生数据类型
content = JSONRenderer().render(serializer.data)  

'''

4、序列化方式2：推荐，serializers.ModelSerializers

# 序列化方式2：serializers.ModelSerializers  (推荐)
"""
1、快捷方式
2、自动，确定一组字段
3、默认实现简单的create与update方法

# 序列化方式2：serializers.ModelSerializers  (推荐)
"""
1、快捷方式
2、自动，确定一组字段
3、默认实现简单的create与update方法
"""
class SnippetSerializer(serializers.ModelSerializer):
    class Meta:
        model = Snippet
        fields = ['id', 'title', 'code', 'linenos', 'language', 'style']

查看所有字段

# 通过打印，序列化器类实例的结构(representation)，查看它的所有字段。
from snippets.serializers import SnippetSerializer
serializer = SnippetSerializer()
print(serializer)
print(repr(serializer))   # repr 规范string形式
# 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')...

5、视图

from django.shortcuts import render

# Create your views here.

from django.http import HttpResponse
from django.views.decorators.csrf import csrf_exempt
from rest_framework.renderers import JSONRenderer   # 渲染器
from rest_framework.parsers import JSONParser       # 解析器

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer


class JSONResponse(HttpResponse):
    """
     一个把content数据，渲染为json数据的HTTPResponse
          An HttpResponse that renders its content into JSON.
    """
    def __init__(self, data, **kwargs):
        content = JSONRenderer().render(data)
        kwargs['content_type'] = 'applications/json'
        super(JSONResponse, self).__init__(content, **kwargs)
        # def __init__(self, content_type=None, status=None, reason=None, charset=None):


# 列出所有现有的snippet或创建一个新的snippet  /snippet
@csrf_exempt  # 从不具有CSRF令牌的客户端对此视图进行POST
def snippet_list(request):
    """
    列出所有的code snippet，或创建1个新的snippet
    """
    if request.method == 'GET':
        snippet = Snippet.objects.all()                         # queryset对象实例
        serializer = SnippetSerializer(snippet, many=True)      # serializer模型实例
        return JSONResponse(serializer.data)                    # 序列化的数据 ReturnDict ---> json

    elif request.method == 'POST':
        data = JSONParser().parse(request)                      # python原生数据 --->  json
        serializer = SnippetSerializer(data=data)               # serializer模型实例
        if serializer.is_valid():                               # data验证
            serializer.save()                                   # 保存到db， 正常的对象实例
            return JSONResponse(serializer.data, status=201)    # 验证通过的data，ReturnDict ---> json
        return JSONResponse(serializer.errors, status=400)      # 未验证的通过的data，


# 一个与单个snippet对象相应的视图 snippet/1
@csrf_exempt
def snippet_detail(request, pk):
    """
    获取，更新，删除1个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 == 'POST':
        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=404)

6、效果