这是我参与11月更文挑战的第11天，活动详情查看：2021最后一次更文挑战
一、基本使用
1.json解析器
同样以订单视图为例，添加json解析器，如下：
from rest_framework.versioning import URLPathVersioning
from rest_framework.parsers import JSONParser
class UserView(APIView):
'''查看用户信息'''
parser_classes = [JSONParser,]
versioning_class =URLPathVersioning
def get(self,request,*args,**kwargs):
res={"name":"wd","age":22}
return JsonResponse(res,safe=True)
def post(self,request,*args,**kwargs):
print(request.data) #获取解析后的请求结果return JsonResponse({"success":"ok"}, safe=True)
使用postman向http://127.0.0.1:8000/api/v1/user 视图发送json数据，注意请求头必须是application/json,如下图：
查看post结果（结果直接是json格式）：
2.form表单解析器
视图
from rest_framework.versioning import URLPathVersioning
from rest_framework.parsers import JSONParser,FormParser
class UserView(APIView):
'''查看用户信息'''
parser_classes = [JSONParser,FormParser]
##JSONParser,解析头信息Content-Type:application/json,的json数据##FormParser，解析头信息Content-Type:x-www-form-urlencoded数据
versioning_class =URLPathVersioning
def get(self,request,*args,**kwargs):
res={"name":"wd","age":22}
return JsonResponse(res,safe=True)
def post(self,request,*args,**kwargs):
print(request.data) #获取解析后的请求结果return JsonResponse({"success":"ok"}, safe=True)
使用postman发送form表单数据
后台接受，并且结果已经转化为QueryDict类型了
二、源码剖析
1.根据以上示例，梳理解析器解析数据流程
- 获取用户请求
- 获取用户请求体
- 根据用户请求头信息和parase_classes=[...],中的请求头进行比较，匹配上请求头就使用该解析器处理
- 解析器从请求体中拿数据进行处理，处理完成之后将结果返回给request.data
2.源码剖析：
同样和权限源码流程一样，请求进来，先执行APIView的dispatch方法，以下是源码，分析请看注解
dispatch方法：
def dispatch(self, request, *args, **kwargs):
"""
`.dispatch()` is pretty much the same as Django's regular dispatch,
but with extra hooks for startup, finalize, and exception handling.
"""
self.args = args
self.kwargs = kwargs
#对原始request进行加工，丰富了一些功能
#Request(
# request,
# parsers=self.get_parsers(),
# authenticators=self.get_authenticators(),
# negotiator=self.get_content_negotiator(),
# parser_context=parser_context
# )
#request(原始request,[BasicAuthentications对象，])
#获取原生request,request._request
#获取认证类的对象，request.authticators
#1.封装request
request = self.initialize_request(request, *args, **kwargs)
self.request = request
self.headers = self.default_response_headers # deprecate?
try:
self.initial(request, *args, **kwargs)
# Get the appropriate handler method
if request.method.lower() in self.http_method_names:
handler = getattr(self, request.method.lower(),
self.http_method_not_allowed)
else:
handler = self.http_method_not_allowed
response = handler(request, *args, **kwargs)
except Exception as exc:
response = self.handle_exception(exc)
self.response = self.finalize_response(request, response, *args, **kwargs)
return self.response
执行initialize_request()方法，在该方法中，get_parsers用于获取解析器，并被封装到request.parsers中。
def initialize_request(self, request, *args, **kwargs):
"""
Returns the initial request object.
"""
parser_context = self.get_parser_context(request)#
return Request(
equest,
parsers=self.get_parsers(), #获取所有的解析器，封装到request.parsers中
authenticators=self.get_authenticators(),
negotiator=self.get_content_negotiator(),
parser_context=parser_context
)
get_parsers()源码，和认证、权限一样，解析器采用列表生成式返回解析器对象的列表，所以示例中定义解析器的变量是parser_classes：
def get_parsers(self):
"""
Instantiates and returns the list of parsers that this view can use.
"""
return [parser() for parser in self.parser_classes] #列表生成式，返回解析器对象
self.praser_classes，默认（全局）配置
class APIView(View):
# The following policies may be set at either globally, or per-view.
renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES
parser_classes = api_settings.DEFAULT_PARSER_CLASSES #解析器全局配置
authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES
throttle_classes = api_settings.DEFAULT_THROTTLE_CLASSES
permission_classes = api_settings.DEFAULT_PERMISSION_CLASSES
content_negotiation_class = api_settings.DEFAULT_CONTENT_NEGOTIATION_CLASS
metadata_class = api_settings.DEFAULT_METADATA_CLASS
versioning_class = api_settings.DEFAULT_VERSIONING_CLASS
当调用request.data获取请求数据时候将使用解析器，下面是request.data源码：
@property
def data(self):
if not _hasattr(self, '_full_data'):
self._load_data_and_files() #执行_load_data_and_files()，获取请求体数据获取文件数据
return self._full_data
执行self._load_data_and_files()，获取请求数据或者文件数据，self._load_data_and_files()源码：
def _load_data_and_files(self):
"""
Parses the request content into `self.data`.
"""
if not _hasattr(self, '_data'):
self._data, self._files = self._parse() #执行self_parse(),获取解析器，并对content_type进行解析，选择解析器，返回数据
if self._files: #判断文件流数据，存在则加入到self._full_data（也就是我们的request.data）中
self._full_data = self._data.copy() ，
self._full_data.update(self._files)
else:
self._full_data = self._data #不存在将无文件流的解析完成的数据赋值到self._full_data(request.data)
# if a form media type, copy data & files refs to the underlying
# http request so that closable objects are handled appropriately.
if is_form_media_type(self.content_type):
self._request._post = self.POST
self._request._files = self.FILES
执行self._prase()方法，获取解析器，并对请求的Content-Type进行解析，选择解析器，返回解析后的数据，以下是self._prase源码：
def _parse(self):
"""
Parse the request content, returning a two-tuple of (data, files)
May raise an `UnsupportedMediaType`, or `ParseError` exception.
"""
media_type = self.content_type # 获取请求体中的Content-Type
try:
stream = self.stream # 如果是文件数据，则获取文件流数据
except RawPostDataException:
if not hasattr(self._request, '_post'):
raise
# If request.POST has been accessed in middleware, and a method='POST'
# request was made with 'multipart/form-data', then the request stream
# will already have been exhausted.
if self._supports_form_parsing():
return (self._request.POST, self._request.FILES) # 处理文件类型数据
stream = None
if stream is None or media_type is None:
if media_type and is_form_media_type(media_type):
empty_data = QueryDict('', encoding=self._request._encoding)
else:
empty_data = {}
empty_files = MultiValueDict()
return (empty_data, empty_files)
parser = self.negotiator.select_parser(self, self.parsers) # 选择解析器，
if not parser:
raise exceptions.UnsupportedMediaType(media_type)
try:
parsed = parser.parse(stream, media_type,
self.parser_context) # 执行解析器的parse方法（从这里可以看出每个解析器都必须有该方法），对请求数据进行解析
except Exception:
# If we get an exception during parsing, fill in empty data and
# re-raise. Ensures we don't simply repeat the error when
# attempting to render the browsable renderer response, or when
# logging the request or similar.
self._data = QueryDict('', encoding=self._request._encoding)
self._files = MultiValueDict()
self._full_data = self._data
raise
# Parser classes may return the raw data, or a
# DataAndFiles object. Unpack the result as required.
try:
return (parsed.data,
parsed.files) # 返回解析结果，元祖，解析后的数据在parsed.data（在load_data_and_files中使用self._data和self._files进行接受）, 文件数据在parsed.files中
except AttributeError:
empty_files = MultiValueDict()
return (parsed, empty_files)
以上就是整个django rest framework 解析器源码，下面我们来看看示例中json解析器的源码，说明请看注解：
class JSONParser(BaseParser):
"""
Parses JSON-serialized data.
"""
media_type = 'application/json' #解析的Content-Type类型
renderer_class = renderers.JSONRenderer
strict = api_settings.STRICT_JSON
def parse(self, stream, media_type=None, parser_context=None): #在源码中解读过，该方法用于解析请求体
"""
Parses the incoming bytestream as JSON and returns the resulting data.
"""
parser_context = parser_context or {}
encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)
try:
decoded_stream = codecs.getreader(encoding)(stream)
parse_constant = json.strict_constant if self.strict else None
return json.load(decoded_stream, parse_constant=parse_constant) #本质使用json类进行解析
except ValueError as exc:
raise ParseError('JSON parse error - %s' % six.text_type(exc))
三、总结
1.解析器本质：
django rest framework解析本质是根据请求头中的Content-Type来实现，不同的类型使用不同的解析器，一个视图可有多个解析器。
2.使用：
#全局使用
REST_FRAMEWORK = {
#解析器"DEFAULT_PARSER_CLASSES":["rest_framework.parsers.JSONParser","rest_framework.parsers.FormParser"]
}
#单一视图使用
parser_classes = [JSONParser,FormParser]
\
