Django Rest Framework源码剖析(二)-----权限

一、简介

上一篇博客中已经介绍了django rest framework 对于认证的源码流程,以及实现过程,当用户经过认证之后下一步就是涉及到权限的问题。比如订单的业务只能VIP才能查看,所以这时候需要对权限进行控制。下面将介绍DRF的权限控制源码剖析。

二、基本使用

这里继续使用之前的示例,加入相应的权限,这里先介绍使用示例,然后在分析权限源码

1.在django 项目下新建立目录utils,并建立permissions.py,添加权限控制:

class MyPremission(object):
message = "您不是会员无权访问"
def has_permission(self,request,view):
if request.user.user_type == 1: ## user_type 为1代表普通用户,则不能查看
return False
return True

2.在订单视图中使用

class OrderView(APIView):
'''查看订单'''
from utils.permissions import MyPremission
authentication_classes = [Authentication,] #添加认证
permission_classes = [MyPremission,] #添加权限
def get(self,request,*args,**kwargs):
#request.user
#request.auth
ret = {'code':1000,'msg':"你的订单已经完成",'data':"买了一个mac"}
return JsonResponse(ret,safe=True)

urls.py

from django.conf.urls import url
from django.contrib import admin
from app01 import views urlpatterns = [ url(r'^api/v1/auth', views.AuthView.as_view()),
url(r'^api/v1/order', views.OrderView.as_view()),
]

models.py

from django.db import models

class UserInfo(models.Model):
user_type_choice = (
(1,"普通用户"),
(2,"会员"),
)
user_type = models.IntegerField(choices=user_type_choice)
username = models.CharField(max_length=32,unique=True)
password = models.CharField(max_length=64) class UserToken(models.Model):
user = models.OneToOneField(to=UserInfo)
token = models.CharField(max_length=64)

3.验证:订单业务同样使用user_type=1的用户进行验证,这里使用工具postman发送请求验证,结果如下:证明我们的权限生效了。

Django Rest Framework源码剖析(二)-----权限

三、权限源码剖析

1.同样请求到达视图时候,先执行APIView的dispatch方法,以下源码是我们在认证篇已经解读过了:

dispatch()

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:
#2.认证
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

2.执行inital方法,initial方法中执行perform_authentication则开始进行认证

 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
#4.实现认证
self.perform_authentication(request)
#5.权限判断
self.check_permissions(request)
self.check_throttles(request)

3.当执行完perform_authentication方法认证通过时候,这时候就进入了本篇文章主题--权限(check_permissions方法),下面是check_permissions方法源码:

    def check_permissions(self, request):
"""
Check if the request should be permitted.
Raises an appropriate exception if the request is not permitted.
"""
for permission in self.get_permissions(): #循环对象get_permissions方法的结果,如果自己没有,则去父类寻找,
if not permission.has_permission(request, self): #判断每个对象中的has_permission方法返回值(其实就是权限判断),这就是为什么我们需要对权限类定义has_permission方法
self.permission_denied(
request, message=getattr(permission, 'message', None) #返回无权限信息,也就是我们定义的message共有属性
)

4.从上源码中我们可以看出,perform_authentication方法中循环get_permissions结果,并逐一判断权限,所以需要分析get_permissions方法返回结果,以下是get_permissions方法源码:

 def get_permissions(self):
"""
Instantiates and returns the list of permissions that this view requires.
"""
return [permission() for permission in self.permission_classes] #与权限一样采用列表生成式获取每个认证类对象

5.get_permissions方法中寻找权限类是通过self.permission_class字段寻找,和认证类一样默认该字段在全局也有配置,如果我们视图类中已经定义,则使用我们自己定义的类。

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
authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES
throttle_classes = api_settings.DEFAULT_THROTTLE_CLASSES
permission_classes = api_settings.DEFAULT_PERMISSION_CLASSES #权限控制
content_negotiation_class = api_settings.DEFAULT_CONTENT_NEGOTIATION_CLASS
metadata_class = api_settings.DEFAULT_METADATA_CLASS
versioning_class = api_settings.DEFAULT_VERSIONING_CLASS

6.承接check_permissions方法,当认证类中的has_permission()方法返回false时(也就是认证不通过),则执行self.permission_denied(),以下是self.permission_denied()源码:

    def permission_denied(self, request, message=None):
"""
If request is not permitted, determine what kind of exception to raise.
"""
if request.authenticators and not request.successful_authenticator:
raise exceptions.NotAuthenticated()
raise exceptions.PermissionDenied(detail=message) # 如果定义了message属性,则抛出属性值

7.认证不通过,则至此django rest framework的权限源码到此结束,相对于认证源码简单一些。

四、内置权限验证类

django rest framework 提供了内置的权限验证类,其本质都是定义has_permission()方法对权限进行验证:

#路径:rest_framework.permissions
##基本权限验证
class BasePermission(object) ##允许所有
class AllowAny(BasePermission) ##基于django的认证权限,官方示例
class IsAuthenticated(BasePermission): ##基于django admin权限控制
class IsAdminUser(BasePermission) ##也是基于django admin
class IsAuthenticatedOrReadOnly(BasePermission)
.....
五、总结

1.使用方法:

  • 继承BasePermission类(推荐)
  • 重写has_permission方法
  • has_permission方法返回True表示有权访问,False无权访问

2.配置:

###全局使用
REST_FRAMEWORK = {
#权限
"DEFAULT_PERMISSION_CLASSES":['API.utils.permission.MyPremission'],
} ##单一视图使用,为空代表不做权限验证
permission_classes = [MyPremission,] ###优先级
单一视图>全局配置
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