Django Rest Framework-----解析器-程序员宅基地

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]