Django Rest Framework-----解析器
为什么要有解析器？原因很简单，当后台和前端进行交互的时候数据类型不一定都是表单数据或者json，当然也有其他类型的数据格式，比如xml，所以需要解析这类数据格式就需要用到解析器(也可以将请求体拿到，然后利用其他模块进行解析)。
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#默认解析器 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
DEFAULTS = { # Base API policies 'DEFAULT_RENDERER_CLASSES': ( 'rest_framework.renderers.JSONRenderer', 'rest_framework.renderers.BrowsableAPIRenderer', ), 'DEFAULT_PARSER_CLASSES': ( 'rest_framework.parsers.JSONParser',#json解析器 'rest_framework.parsers.FormParser',#form解析器 'rest_framework.parsers.MultiPartParser'#二进制解析器 ),#rest_framework 默认支持三种解析器
json解析器
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/login视图发送json数据，注意请求头必须是application/json,如下图：
from rest_framework.parsers import JSONParser class LoginViewSet(APIView): parser_classes = [JSONParser, ] authentication_classes = [] def post(self,request): name = request.data.get('name') pwd = request.data.get('pwd') user = User.objects.filter(name=name,pwd=pwd).first() res = {"state_code":1000,"msg":None} if user: token =get_random_str(user.name) Token.objects.update_or_create(user=user,defaults={"token":token}) res['token'] = token # return Response('ok') else: res["state_code"] = 1001 res["msg"] = "用户名或密码错误" import json return Response(res)
form表单解析器
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
源码剖析
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
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
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( request, 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#默认解析器配置 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 # Allow dependency injection of other settings to make testing easier. settings = api_settings schema = DefaultSchema()
#rest_framework默认全局配置
DEFAULTS = { # Base API policies 'DEFAULT_RENDERER_CLASSES': ( 'rest_framework.renderers.JSONRenderer', 'rest_framework.renderers.BrowsableAPIRenderer', ), 'DEFAULT_PARSER_CLASSES': ( 'rest_framework.parsers.JSONParser', 'rest_framework.parsers.FormParser', 'rest_framework.parsers.MultiPartParser' ), 'DEFAULT_AUTHENTICATION_CLASSES': ( 'rest_framework.authentication.SessionAuthentication', 'rest_framework.authentication.BasicAuthentication' ), 'DEFAULT_PERMISSION_CLASSES': ( 'rest_framework.permissions.AllowAny', ), 'DEFAULT_THROTTLE_CLASSES': (), 'DEFAULT_CONTENT_NEGOTIATION_CLASS': 'rest_framework.negotiation.DefaultContentNegotiation', 'DEFAULT_METADATA_CLASS': 'rest_framework.metadata.SimpleMetadata', 'DEFAULT_VERSIONING_CLASS': None, # Generic view behavior 'DEFAULT_PAGINATION_CLASS': None, 'DEFAULT_FILTER_BACKENDS': (), # Schema 'DEFAULT_SCHEMA_CLASS': 'rest_framework.schemas.AutoSchema', # Throttling 'DEFAULT_THROTTLE_RATES': { 'user': None, 'anon': None, }, 'NUM_PROXIES': None, # Pagination 'PAGE_SIZE': None, # Filtering 'SEARCH_PARAM': 'search', 'ORDERING_PARAM': 'ordering', # Versioning 'DEFAULT_VERSION': None, 'ALLOWED_VERSIONS': None, 'VERSION_PARAM': 'version', # Authentication 'UNAUTHENTICATED_USER': 'django.contrib.auth.models.AnonymousUser', 'UNAUTHENTICATED_TOKEN': None, # View configuration 'VIEW_NAME_FUNCTION': 'rest_framework.views.get_view_name', 'VIEW_DESCRIPTION_FUNCTION': 'rest_framework.views.get_view_description', # Exception handling 'EXCEPTION_HANDLER': 'rest_framework.views.exception_handler', 'NON_FIELD_ERRORS_KEY': 'non_field_errors', # Testing 'TEST_REQUEST_RENDERER_CLASSES': ( 'rest_framework.renderers.MultiPartRenderer', 'rest_framework.renderers.JSONRenderer' ), 'TEST_REQUEST_DEFAULT_FORMAT': 'multipart', # Hyperlink settings 'URL_FORMAT_OVERRIDE': 'format', 'FORMAT_SUFFIX_KWARG': 'format', 'URL_FIELD_NAME': 'url', # Input and output formats 'DATE_FORMAT': ISO_8601, 'DATE_INPUT_FORMATS': (ISO_8601,), 'DATETIME_FORMAT': ISO_8601, 'DATETIME_INPUT_FORMATS': (ISO_8601,), 'TIME_FORMAT': ISO_8601, 'TIME_INPUT_FORMATS': (ISO_8601,), # Encoding 'UNICODE_JSON': True, 'COMPACT_JSON': True, 'STRICT_JSON': True, 'COERCE_DECIMAL_TO_STRING': True, 'UPLOADED_FILES_USE_URL': True, # Browseable API 'HTML_SELECT_CUTOFF': 1000, 'HTML_SELECT_CUTOFF_TEXT': "More than {count} items...", # Schemas 'SCHEMA_COERCE_PATH_PK': True, 'SCHEMA_COERCE_METHOD_NAMES': { 'retrieve': 'read', 'destroy': 'delete' }, }
#APISettings源码解析 def perform_import(val, setting_name): """ If the given setting is a string import notation, then perform the necessary import or imports. """ if val is None: return None elif isinstance(val, six.string_types): return import_from_string(val, setting_name) elif isinstance(val, (list, tuple)): return [import_from_string(item, setting_name) for item in val] return val def import_from_string(val, setting_name): """ Attempt to import a class from a string representation. """ try: # Nod to tastypie's use of importlib. module_path, class_name = val.rsplit('.', 1) module = import_module(module_path) return getattr(module, class_name) except (ImportError, AttributeError) as e: msg = "Could not import '%s' for API setting '%s'. %s: %s." % (val, setting_name, e.__class__.__name__, e) raise ImportError(msg) class APISettings(object): """ A settings object, that allows API settings to be accessed as properties. For example: from rest_framework.settings import api_settings print(api_settings.DEFAULT_RENDERER_CLASSES) Any setting with string import paths will be automatically resolved and return the class, rather than the string literal. """ 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: raise AttributeError("Invalid API setting: '%s'" % attr) try: # Check if present in user settings 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 def __check_user_settings(self, user_settings): SETTINGS_DOC = "https://www.django-rest-framework.org/api-guide/settings/" for setting in REMOVED_SETTINGS: if setting in user_settings: raise RuntimeError("The '%s' setting has been removed. Please refer to '%s' for available settings." % (setting, SETTINGS_DOC)) return user_settings def reload(self): for attr in self._cached_attrs: delattr(self, attr) self._cached_attrs.clear() if hasattr(self, '_user_settings'): delattr(self, '_user_settings') api_settings = APISettings(None, DEFAULTS, IMPORT_STRINGS)#生成类对象,user_setting没有传值. def reload_api_settings(*args, **kwargs): setting = kwargs['setting'] if setting == 'REST_FRAMEWORK': api_settings.reload() setting_changed.connect(reload_api_settings)
源码解析思路通认证一样只是填写参数不一样.
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#装饰器将方法变成实例对象.函数名的形式 def data(self): if not _hasattr(self, '_full_data'): self._load_data_and_files() return self._full_data
#Request类属性源码展示 class Request(object): """ Wrapper allowing to enhance a standard `HttpRequest` instance. Kwargs: - request(HttpRequest). The original request instance. - parsers_classes(list/tuple). The parsers to use for parsing the request content. - authentication_classes(list/tuple). The authentications used to try authenticating the request's user. """ def __init__(self, request, parsers=None, authenticators=None, negotiator=None, parser_context=None): assert isinstance(request, HttpRequest), ( 'The `request` argument must be an instance of ' '`django.http.HttpRequest`, not `{}.{}`.' .format(request.__class__.__module__, request.__class__.__name__) ) self._request = request self.parsers = parsers or () self.authenticators = authenticators or () self.negotiator = negotiator or self._default_negotiator() self.parser_context = parser_context self._data = Empty self._files = Empty self._full_data = Empty self._content_type = Empty self._stream = Empty if self.parser_context is None: self.parser_context = {} self.parser_context['request'] = self self.parser_context['encoding'] = request.encoding or settings.DEFAULT_CHARSET
因为_full_data为空所以执行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)
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:
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))
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。
#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]
