一、请求到来之后，都要先执行dispatch方法，dispatch方法方法根据请求方式的不同触发get/post/put/delete等方法
注意，APIView中的dispatch方法有很多的功能
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 第一步：对request进行加工（添加数据） request = self.initialize_request(request, *args, **kwargs) self.request = request self.headers = self.default_response_headers # deprecate? try: #第二步： #处理版权信息 #认证 #权限 #请求用户进行访问频率的限制 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 # 第三步、执行：get/post/put/delete函数 response = handler(request, *args, **kwargs) except Exception as exc: response = self.handle_exception(exc) #第四步、 对返回结果再次进行加工 self.response = self.finalize_response(request, response, *args, **kwargs) return self.response
二、上面是大致步骤，下面我们来具体分析一下，看每个步骤中都具体干了什么事
1、对request进行加工（添加数据）
我们来看看request里面都添加了那些数据
a、首先 request = self.initialize_request(request, *args, **kwargs)点进去，会发现：在Request里面多加了四个，如下
def initialize_request(self, request, *args, **kwargs): """ Returns the initial request object. """ #吧请求弄成一个字典返回了 parser_context = self.get_parser_context(request) return Request( request, parsers=self.get_parsers(), #解析数据，默认的有三种方式，可点进去看 #self.get_authenticator优先找自己的，没有就找父类的 authenticators=self.get_authenticators(), #获取认证相关的所有类并实例化，传入request对象供Request使用 negotiator=self.get_content_negotiator(), parser_context=parser_context )
b、获取认证相关的类的具体 authenticators=self.get_authenticators(),
def get_authenticators(self): """ Instantiates and returns the list of authenticators that this view can use. """ #返回的是对象列表 return [auth() for auth in self.authentication_classes] #[SessionAuthentication,BaseAuthentication]
c、查看认证的类：self.authentication_classes
authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES #默认的，如果自己有会优先执行自己的
d、接着走进api_settings
api_settings = APISettings(None, DEFAULTS, IMPORT_STRINGS) #点击继承的DEFAULTS类
DEFAULTS = { # Base API policies 'DEFAULT_AUTHENTICATION_CLASSES': ( 'rest_framework.authentication.SessionAuthentication', #这时候就找到了他默认认证的类了，可以导入看看 'rest_framework.authentication.BasicAuthentication' ),
e、导入了类看看类里面具体干了什么
from rest_framework.authentication import SessionAuthentication from rest_framework.authentication import BaseAuthentication
f、看到里面有个authenticate方法和authenticate_header方法
class BaseAuthentication(object): """ All authentication classes should extend BaseAuthentication. """ def authenticate(self, request): """ Authenticate the request and return a two-tuple of (user, token). """ raise NotImplementedError(".authenticate() must be overridden.") def authenticate_header(self, request): """ Return a string to be used as the value of the `WWW-Authenticate` header in a `401 Unauthenticated` response, or `None` if the authentication scheme should return `403 Permission Denied` responses. """ pass
具体处理认证，从headers里面能获取用户名和密码
class BasicAuthentication(BaseAuthentication): """ HTTP Basic authentication against username/password. """ www_authenticate_realm = 'api' def authenticate(self, request): """ Returns a `User` if a correct username and password have been supplied using HTTP Basic authentication. Otherwise returns `None`. """ auth = get_authorization_header(request).split() if not auth or auth[0].lower() != b'basic': return None #返回none不处理。让下一个处理 if len(auth) == 1: msg = _('Invalid basic header. No credentials provided.') raise exceptions.AuthenticationFailed(msg) elif len(auth) > 2: msg = _('Invalid basic header. Credentials string should not contain spaces.') raise exceptions.AuthenticationFailed(msg) try: auth_parts = base64.b64decode(auth[1]).decode(HTTP_HEADER_ENCODING).partition(':') #用partition切割冒号也包括 except (TypeError, UnicodeDecodeError, binascii.Error): msg = _('Invalid basic header. Credentials not correctly base64 encoded.') raise exceptions.AuthenticationFailed(msg) userid, password = auth_parts[0], auth_parts[2] # 返回用户和密码 return self.authenticate_credentials(userid, password, request) def authenticate_credentials(self, userid, password, request=None): """ Authenticate the userid and password against username and password with optional request for context. """ credentials = { get_user_model().USERNAME_FIELD: userid, 'password': password } user = authenticate(request=request, **credentials) if user is None: raise exceptions.AuthenticationFailed(_('Invalid username/password.')) if not user.is_active: raise exceptions.AuthenticationFailed(_('User inactive or deleted.')) return (user, None) def authenticate_header(self, request): return 'Basic realm="%s"' % self.www_authenticate_realm
g、当然restfulframework默认定义了两个类。我们也可以自定制类，自己有就用自己的了，自己没有就去找父类的了，但是里面必须实现authenticate方法，不然会报错。
2、进行一下操作
- 处理版权信息
- 认证
- 权限
- 请求用户进行访问频率的限制
我们主要来看一下认证流程
认证流程：
a、首先 self.initial(request, *args, **kwargs)可以看到做了以下操作
def initial(self, request, *args, **kwargs): """ Runs anything that needs to occur prior to calling the method handler. """ self.format_kwarg = self.get_format_suffix(**kwargs) # Perform content negotiation and store the accepted info on the request neg = self.perform_content_negotiation(request) request.accepted_renderer, request.accepted_media_type = neg # Determine the API version, if versioning is in use. #2.1 处理版本信息 version, scheme = self.determine_version(request, *args, **kwargs) request.version, request.versioning_scheme = version, scheme # Ensure that the incoming request is permitted #2.2 认证 self.perform_authentication(request) # 2.3 权限 self.check_permissions(request) # 2.4 请求用户进行访问频率的限制 self.check_throttles(request)
b、我们先来看认证，self.perform_authentication(request) 具体干了什么，按住ctrl点击进去
def perform_authentication(self, request): """ Perform authentication on the incoming request. Note that if you override this and simply 'pass', then authentication will instead be performed lazily, the first time either `request.user` or `request.auth` is accessed. """ request.user #执行request的user，这是的request已经是加工后的request了
c、那么我们可以从视图里面导入一下Request，找到request对象的user方法
from rest_framework.views import Request
@property def user(self): """ Returns the user associated with the current request, as authenticated by the authentication classes provided to the request. """ if not hasattr(self, '_user'): with wrap_attributeerrors(): self._authenticate() # return self._user #返回user
d、执行self._authenticate() 开始用户认证，如果验证成功后返回元组： (用户,用户Token)
def _authenticate(self): """ Attempt to authenticate the request using each authentication instance in turn. """ #循环对象列表 for authenticator in self.authenticators: try: #执行每一个对象的authenticate 方法 user_auth_tuple = authenticator.authenticate(self) except exceptions.APIException: self._not_authenticated() raise if user_auth_tuple is not None: self._authenticator = authenticator self.user, self.auth = user_auth_tuple #返回一个元组，user，和auth，赋给了self, # 只要实例化Request，就会有一个request对象，就可以request.user,request.auth了 return self._not_authenticated()
e、在user_auth_tuple = authenticator.authenticate(self) 进行验证，如果验证成功，执行类里的authenticatie方法
f、如果用户没有认证成功：self._not_authenticated()
def _not_authenticated(self): """ Set authenticator, user & authtoken representing an unauthenticated request. Defaults are None, AnonymousUser & None. """ #如果跳过了所有认证，默认用户和Token和使用配置文件进行设置 self._authenticator = None # if api_settings.UNAUTHENTICATED_USER: self.user = api_settings.UNAUTHENTICATED_USER() # 默认值为：匿名用户AnonymousUser else: self.user = None # None 表示跳过该认证 if api_settings.UNAUTHENTICATED_TOKEN: self.auth = api_settings.UNAUTHENTICATED_TOKEN() # 默认值为：None else: self.auth = None # (user, token) # 表示验证通过并设置用户名和Token； # AuthenticationFailed异常
3、执行get/post/delete等方法
4、对返回结果在进行加工
