QUESTION:post方法中调用request.data方法时，当在Courseview类中添加parser_classes=[ForParser,]，
就可以将数据解析成parser_classes中的数据格式，并且在request.data中打印。为什么？
答：当打印request.data时走源码时，最终会走到[parser() for parser in self.parser_classes] ，
源码的解析方法很简单，使用json序列化和反序列化即可，关键问题是使用的谁的解析方式？是自己写的、还是默认的、还是全局的？
配置parser_classes有三种方式：自己的类（CourseView）下边配置、在全局settings中配置、在defaults中配置。
执行顺序：如果在自己的类下配置，就优先执行自己类中的parser_classes即可，如果没有就在settings中配置parser_classes即可，
如果不在settings中配置，那么就使用默认的global_settings中的即可。
**
class APIView(View):
def dispatch(self, request, *args, **kwargs): #由于新的request在dispatch方法中
self.args = args
self.kwargs = kwargs
request = self.initialize_request(request, *args, **kwargs)
self.request = request
self.headers = self.default_response_headers # deprecate?
**
def initialize_request(self, request, *args, **kwargs):
parser_context = self.get_parser_context(request)
return Request(
request,
parsers=self.get_parsers(),
authenticators=self.get_authenticators(),
negotiator=self.get_content_negotiator(),
parser_context=parser_context
)
**
a.点击self.get_parsers()
def get_parsers(self):
return [parser() for parser in self.parser_classes] #将parser_classes中的解析方法遍历，实例化即可
**
class APIView(View):
renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES
parser_classes = api_settings.DEFAULT_PARSER_CLASSES
authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES
api_settings = APISettings(None, DEFAULTS, IMPORT_STRINGS)
class APISettings(object):
def __init__(self, user_settings=None, defaults=None, import_strings=None):
if user_settings:
self._user_settings = self.__check_user_settings(user_settings)
self.defaults = defaults or DEFAULTS
self.import_strings = import_strings or IMPORT_STRINGS
self._cached_attrs = set()
@property
def user_settings(self):
if not hasattr(self, '_user_settings'):
self._user_settings = getattr(settings, 'REST_FRAMEWORK', {})
return self._user_settings
def __getattr__(self, attr):
if attr not in self.defaults: #defaults默认为空
raise AttributeError("Invalid API setting: '%s'" % attr)
try:
# Check if present in user settings
val = self.user_settings[attr] #a.如果在全局的settings中没有配置REST_FRAMEWORK,那么
elf.user_settings为空，就走except。settings中配置格式为：
REST_FRAMEWORK=[
'DEFAULT_PARSER_CLASSES': (
'rest_framework.parsers.JSONParser',
'rest_framework.parsers.FormParser',
'rest_framework.parsers.MultiPartParser'
),
]
except KeyError: # Fall back to defaults
val = self.defaults[attr] #b.在defaults中找DEFAULT_PARSER_CLASSES，
可以找到，因为默认的写了这个
return val
b.点击Request类
class Request(object):
@property
def data(self):
if not _hasattr(self, '_full_data'):
self._load_data_and_files()
return self._full_data
**
def _load_data_and_files(self):
if not _hasattr(self, '_data'):
self._data, self._files = self._parse()
if self._files:
self._full_data = self._data.copy()
self._full_data.update(self._files)
else:
self._full_data = self._data
**
def _parse(self):
media_type = self.content_type
try:
stream = self.stream
except RawPostDataException:
if not hasattr(self._request, '_post'):
raise
if self._supports_form_parsing():
return (self._request.POST, self._request.FILES)
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)
**
def select_parser(self, request, parsers):
for parser in parsers:
if media_type_matches(parser.media_type, request.content_type):
return parser
return None
