premission组件源码剖析:
第一步，当接收到请求，drf会通过dispatch()对request进行处理
class APIView(View):
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
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
对于权限组件，在dispatch中主要看
self.initial(request, *args, **kwargs)
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.
version, scheme = self.determine_version(request, *args, **kwargs)
request.version, request.versioning_scheme = version, scheme
# Ensure that the incoming request is permitted
self.perform_authentication(request) #认证组件，循环执行每一个authticatef方法，失败会抛出异常
self.check_permissions(request) #权限组件#执行到这里时是通过认证或者所有认证类都返回none，在认证类最后中可加入一个检测是否认证成功的类，到此时可确保request.user&auth
self.check_throttles(request)
执行权限组件时
self.check_permissions(request)
def permission_denied(self, request, message=None, code=None):
#权限等于False,则抛出异常，返回的message和code默认为none，可在认证类中自定义
if request.authenticators and not request.successful_authenticator:
raise exceptions.NotAuthenticated()
raise exceptions.PermissionDenied(detail=message, code=code)
def get_permissions(self):
#读取permission_classes中的类并实例化成对象，读取顺序参照上一篇认证组件
return [permission() for permission in self.permission_classes]
def check_permissions(self, request):
for permission in self.get_permissions():
#执行每个权限类的has_permission，如果等于False则进入下方的permission_denied
if not permission.has_permission(request, self):
#认证不通过抛出会进入permission_denied抛出异常
self.permission_denied(
request,
message=getattr(permission, 'message', None),
code=getattr(permission, 'code', None)
)
自定义认证类的返回的错误信息
class Mypermission(BasePermission):
#自定义错误信息
message = {"code":10011,"msg":"无权访问"}
def has_permission(self,request,view):
a=random.randint(1,3)
if a ==2:
return True
else:
return False
抛出异常时的返回信息
{"code":"10011","msg":"无权访问"}
permission_denied抛出的异常会被dispatch捕获到，执行except后的处理异常的方法。
现有的权限认证的机制时当所有的认证类都返回True时才能继续执行，能不能改成只要通过一个权限类就可以继续执行下面的代码呢？可以通过修改check_permissions实现。在我们自定义的权限类中可以重写check_permissions：
def check_permissions(self, request):
permission_err_list=[]
for permission in self.get_permissions():
if permission.has_permission(request, self):
return
else:
permission_err_list.append(permission)
else:
self.permission_denied( request,message=getattr(permission_err_list[0], 'message', None), code=getattr(permission_err_list[0], 'code', None))
