rest-framework 解析器

一 解析器的作用:

　　根据请求头 content-type 选择对应的解析器对请求体内容进行处理。

　　有application/json，x-www-form-urlencoded，form-data等格式　

   urlencoded：在body体中的格式是：name=lqz&age=18&wife=liuyifei
   formdata:在body体中的格式数据部分跟文件部分有区分
   json格式：在body体中就是json格式

二 全局使用解析器:

在settings.py中

REST_FRAMEWORK = {
    'DEFAULT_PARSER_CLASSES':[
        'rest_framework.parsers.JSONParser'

        'rest_framework.parsers.FormParser'

        'rest_framework.parsers.MultiPartParser'
    ]

}

视图层：

from rest_framework.views import APIView
from rest_framework.response import Response

class TestView(APIView):
    def post(self, request, *args, **kwargs):
        print(request.content_type)

        # 获取请求的值，并使用对应的JSONParser进行处理
        print(request.data)
        # application/x-www-form-urlencoded 或 multipart/form-data时，request.POST中才有值
        print(request.POST)
        print(request.FILES)
        return Response('POST请求，响应内容')

    def put(self, request, *args, **kwargs):
        return Response('PUT请求，响应内容')

三 局部使用解析器：

仅处理请求头content-type为application/json的请求体

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.request import Request
from rest_framework.parsers import JSONParser

class TestView(APIView):

    parser_classes = [JSONParser, ]

    def post(self, request, *args, **kwargs):
        print(request.content_type)

        # 获取请求的值，并使用对应的JSONParser进行处理
        print(request.data)

        # application/x-www-form-urlencoded 或 multipart/form-data时，request.POST中才有值
        print(request.POST)
        print(request.FILES)

        return Response('POST请求，响应内容')

    def put(self, request, *args, **kwargs):
        return Response('PUT请求，响应内容')

请求头content-type为application/x-www-form-urlencoded 的请求体

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.request import Request
from rest_framework.parsers import FormParser

class TestView(APIView):

    parser_classes = [FormParser, ]

    def post(self, request, *args, **kwargs):
        print(request.content_type)

请求头content-type为multipart/form-data的请求体

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.request import Request
from rest_framework.parsers import MultiPartParser

class TestView(APIView):

    parser_classes = [MultiPartParser, ]

    def post(self, request, *args, **kwargs):
        print(request.content_type)

上传文件：

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.request import Request
from rest_framework.parsers import FileUploadParser

class TestView(APIView):

    parser_classes = [FileUploadParser, ]

同时多个Parser

当同时使用多个parser时，rest framework会根据请求头content-type自动进行比对，并使用对应parser

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.request import Request
from rest_framework.parsers import JSONParser, FormParser, MultiPartParser

class TestView(APIView):

    parser_classes = [JSONParser, FormParser, MultiPartParser, ]


    def post(self, request, *args, **kwargs):
        print(request.content_type)

四 源码分析：

1 在调用request.data时，才进行解析，由此入手
    @property
    def data(self):
        if not _hasattr(self, '_full_data'):
            self._load_data_and_files()
        return self._full_data

2 查看self._load_data_and_files()方法---->self._data, self._files = self._parse()

        def _parse(self):
            #用户请求头里content_type的值
            media_type = self.content_type

            #self.parsers 就是用户配置的parser_classes = [FileUploadParser,FormParser ]
            #self里就有content_type，传入此函数
            parser = self.negotiator.select_parser(self, self.parsers)

3 查看self.negotiator.select_parser(self, self.parsers)
     def select_parser(self, request, parsers):
        #同过media_type和request.content_type比较，来返回解析器，然后调用解析器的解析方法
        #每个解析器都有media_type = 'multipart/form-data'属性
        for parser in parsers:
            if media_type_matches(parser.media_type, request.content_type):
                return parser
        return None

4 最终调用parser的解析方法来解析parsed = parser.parse(stream, media_type, self.parser_context)

1 Request实例化，parsers=self.get_parsers()
    Request(
                request,
                parsers=self.get_parsers(),
                authenticators=self.get_authenticators(),
                negotiator=self.get_content_negotiator(),
                parser_context=parser_context
            )
2 get_parsers方法，循环实例化出self.parser_classes中类对象
    def get_parsers(self):
        return [parser() for parser in self.parser_classes]            

3 self.parser_classes 先从类本身找，找不到去父类找即APIVIew 中的
    parser_classes = api_settings.DEFAULT_PARSER_CLASSES
4 api_settings是一个对象，对象里找DEFAULT_PARSER_CLASSES属性，找不到，会到getattr方法
        def __getattr__(self, attr):
            if attr not in self.defaults:
                raise AttributeError("Invalid API setting: '%s'" % attr)

            try:
                #调用self.user_settings方法，返回一个字典，字典再取attr属性
                val = self.user_settings[attr]
            except KeyError:
                # Fall back to defaults
                val = self.defaults[attr]

            # Coerce import strings into classes
            if attr in self.import_strings:
                val = perform_import(val, attr)

            # Cache the result
            self._cached_attrs.add(attr)
            setattr(self, attr, val)
            return val
 5 user_settings方法 ，通过反射去setting配置文件里找REST_FRAMEWORK属性，找不到，返回空字典
    @property
    def user_settings(self):
        if not hasattr(self, '_user_settings'):
            self._user_settings = getattr(settings, 'REST_FRAMEWORK', {})
        return self._user_settings

源码流程：
   -当调用request.data的时候去执行解析方法----》根据传过来的编码方式选择一个解析器对象，调用解析器对象的parser方法完成解析