Django

Django restframework源码解读第一节

初始restframework源码

Posted by QQL on January 20, 2019

Django restframework第一节

  1. 开发模式
    • 普通开发方式（前后端放在一起写）
    • 前后端分离
  2. 后端开发
    • 为前端提供URL（API/接口的开发）
    • 注：永远返回HttpResponse
  3. Django FBV、CBV

FBV,function base view

def users(request):
	user_list = ['alex','oldboy']
	return HttpResponse(json.dumps((user_list)))

CBV,class base view

路由： url(r'^students/', views.StudentsView.as_view()),

视图：

from django.views import View

class StudentsView(View):

	def get(self,request,*args,**kwargs):
		return HttpResponse('GET')

	def post(self, request, *args, **kwargs):
		return HttpResponse('POST')

	def put(self, request, *args, **kwargs):
		return HttpResponse('PUT')

	def delete(self, request, *args, **kwargs):
		return HttpResponse('DELETE')

4.面向对象
封装：
对同一类方法封装到类中

class File:
	文件增删改查方法
	
Class DB:
	数据库的方法

将数据封装到对象中

class File:
	def __init__(self,a1,a2):
		self.a1 = a1 
		self.xxx = a2
	def get:...
	def delete:...
	def update:...
	def add:...
	
obj1 = File(123,666)
obj2 = File(456,999)

私有属性/方法
self.__name = name

FBV、CBV

CBV，基于反射实现根据请求方式不同，执行不同的方法。
原理：

url -> view方法 -> dispatch方法（反射执行自定义的其他：GET/POST/DELETE/PUT）—>执行后再次把执行的结果返回给dipatch返回给View—>传给url–>传给客户端

流程：

class StudentsView(View):
	# 本质上CBV发送请求先要获取请求方式，则始终要走dispatch,通过反射getattr(self, request.method)在自定义类的对象中获取请求方法，请求方式需要自己定义def get/def post....

	def dispatch(self, request, *args, **kwargs):
		print('before')  # 可以在dispatch实现其他操作，类似于装饰器的功能
		ret = super(StudentsView,self).dispatch(request, *args, **kwargs)
		print('after')  # 视图函数get/post/put/delete...执行完后执行操作
		return ret

	def get(self,request,*args,**kwargs):
		return HttpResponse('GET')

	def post(self, request, *args, **kwargs):
		return HttpResponse('POST')

	def put(self, request, *args, **kwargs):
		return HttpResponse('PUT')

	def delete(self, request, *args, **kwargs):
		return HttpResponse('DELETE')

继承（多个类共用的功能，为了避免重复编写）：
from django.views import View


class MyBaseView(object):
	def dispatch(self, request, *args, **kwargs):
		print('before')
		# super实现以继承顺序(__mro__可以查看顺序)查找父类的.dispatch()方法
		ret = super(MyBaseView,self).dispatch(request, *args, **kwargs)
		print('after')
		return ret

class StudentsView(MyBaseView,View):  # 从左到右继承顺序

	def get(self,request,*args,**kwargs):
		print('get方法')
		return HttpResponse('GET')

	def post(self, request, *args, **kwargs):
		return HttpResponse('POST')

	def put(self, request, *args, **kwargs):
		return HttpResponse('PUT')

	def delete(self, request, *args, **kwargs):
		return HttpResponse('DELETE')

class TeachersView(MyBaseView,View):

	def get(self,request,*args,**kwargs):
		return HttpResponse('GET')

	def post(self, request, *args, **kwargs):
		return HttpResponse('POST')

	def put(self, request, *args, **kwargs):
		return HttpResponse('PUT')

	def delete(self, request, *args, **kwargs):
		return HttpResponse('DELETE')

面试题

  1. django中间件
    • process_request
    • process_view
    • process_response
    • process_exception
    • process_render_template

中间键流程完整流程：
用户–>WSGI–>每个中间键(可以有多个)的process_request—>走完所有中间键的process_request将倒回来—>走每个中间键的process_view—>视图函数中处理业务逻辑–>template/ORM交互数据库—>如果视图函数中有render，走中间键process_render_template返回给用户/如果视图函数中抛出异常，走中间键process_exception返回给用户错误信息

  1. 使用中间件做过什么？
    • 权限
    • 用户登录验证
    • django的csrf是如何实现？ csrf放在中间键process_view中而不是precess_request，因为csrf要先在视图函数中查看访问的视图是否加了装饰器csrf_exempt process_view方法
    • 检查视图是否被 @csrf_exempt （免除csrf认证）
    • 装饰器需要导入： from django.views.decorators.csrf import csrf_exempt - 去请求体或cookie中获取token
  2. 不使用csrf认证
    情况一：
    ``` settings.py

MIDDLEWARE = [ ‘django.middleware.security.SecurityMiddleware’, ‘django.contrib.sessions.middleware.SessionMiddleware’, ‘django.middleware.common.CommonMiddleware’, ‘django.middleware.csrf.CsrfViewMiddleware’, # 全站使用csrf认证 ‘django.contrib.auth.middleware.AuthenticationMiddleware’, ‘django.contrib.messages.middleware.MessageMiddleware’, ‘django.middleware.clickjacking.XFrameOptionsMiddleware’, ]

views.py

from django.views.decorators.csrf import csrf_exempt @csrf_exempt # 该函数无需认证 def users(request): user_list = [‘alex’,’oldboy’] return HttpResponse(json.dumps((user_list)))


情况二：

settings.py

MIDDLEWARE = [ ‘django.middleware.security.SecurityMiddleware’, ‘django.contrib.sessions.middleware.SessionMiddleware’, ‘django.middleware.common.CommonMiddleware’, #’django.middleware.csrf.CsrfViewMiddleware’, # 全站不使用csrf认证 ‘django.contrib.auth.middleware.AuthenticationMiddleware’, ‘django.contrib.messages.middleware.MessageMiddleware’, ‘django.middleware.clickjacking.XFrameOptionsMiddleware’, ]

views.py

from django.views.decorators.csrf import csrf_exempt,csrf_protect @csrf_protect # 该函数需认证 def users(request): user_list = [‘alex’,’oldboy’] return HttpResponse(json.dumps((user_list)))



### CBV小知识  
**CBV无法给方法(get/post/delete...)添加装饰器！！！**  
**解决办法**：  
csrf时需要使用  
`from django.utils.decorators import method_decorator`  
`@method_decorator(csrf_exempt)`  
装饰器给dispatch方法中（装饰单独方法(get/post/put...)无效）  


方式一：

from django.views.decorators.csrf import csrf_exempt,csrf_protect from django.utils.decorators import method_decorator class StudentsView(View):

@method_decorator(csrf_exempt)
def dispatch(self, request, *args, **kwargs):
	return super(StudentsView,self).dispatch(request, *args, **kwargs)

def get(self,request,*args,**kwargs):
	print('get方法')
	return HttpResponse('GET')

def post(self, request, *args, **kwargs):
	return HttpResponse('POST')

def put(self, request, *args, **kwargs):
	return HttpResponse('PUT')

def delete(self, request, *args, **kwargs):
	return HttpResponse('DELETE') ```   方式二：     ``` from django.views.decorators.csrf import csrf_exempt,csrf_protect from django.utils.decorators import method_decorator

@method_decorator(csrf_exempt,name=’dispatch’) # 装饰给类 class StudentsView(View):

def get(self,request,*args,**kwargs):
	print('get方法')
	return HttpResponse('GET')

def post(self, request, *args, **kwargs):
	return HttpResponse('POST')

def put(self, request, *args, **kwargs):
	return HttpResponse('PUT')

def delete(self, request, *args, **kwargs):
	return HttpResponse('DELETE') ```

总结

  • 本质，基于反射来实现
  • 流程：路由，view，dispatch(反射)
  • 取消csrf认证（装饰器要加到dispatch方法上且method_decorator装饰）

扩展：

  • csrf
    • 基于中间件的process_view方法
    • 装饰器给单独函数进行设置（认证或无需认证）

django rest framework框架

pip3 install djangorestframework
from rest_framework.views import APIView

01.进入APIView源码，发现class APIView(View):pass 继承了View只是在原有的基础上，添加了新的功能

02.找到APIView中的dispatch()方法，重写了原View的dispatch，给request对象，封装了新的属性

def dispatch(self, request, *args, **kwargs):
	self.args = args
	self.kwargs = kwargs
	# 将原有的request 加工分装了新的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

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(),  # 拿到一个列表生成式，生成一个对象列表[obj1,obj2....]
		authenticators=self.get_authenticators(),  # 拿到一个列表生成式，生成一个对象列表[obj1,obj2....]
		negotiator=self.get_content_negotiator(),
		parser_context=parser_context
	)

04.parsers和authenticators两个列表生成式
找self.parser_classes，self为自定义的class对象
当自己的class没有定义parser_classes找继承的父类APIView是否有parser_classes

def get_parsers(self):
	return [parser() for parser in self.parser_classes]

def get_authenticators(self):
	return [auth() for auth in self.authentication_classes]

05.在继承的父类APIView中找到parser_classes和authentication_classes

class APIView(View):
	...
	renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES
	parser_classes = api_settings.DEFAULT_PARSER_CLASSES
	authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES
	...

06.在initialize_request返回的对象Request中

class Request(object):
	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  # 原生的request分装成了_request
		self.parsers = parsers or ()
		self.authenticators = authenticators or ()  # .authenticators可进行验证
		........
	......

authenticator认证仅使用：

from django.views import View
from rest_framework.views import APIView
from rest_framework.authentication import BasicAuthentication
from rest_framework import exceptions
from rest_framework.request import Request

class MyAuthentication(object):
	def authenticate(self,request):
		token = request._request.GET.get('token')
		# 获取用户名和密码，去数据校验
		if not token:
			raise exceptions.AuthenticationFailed('用户认证失败')
		return ("alex",None)

	def authenticate_header(self,val):
		pass

class DogView(APIView):
	authentication_classes = [MyAuthentication,]

	def get(self,request,*args,**kwargs):
		print(request)
		print(request.user)
		ret  = {
			'code':1000,
			'msg':'xxx'
		}
		return HttpResponse(json.dumps(ret),status=201)

	def post(self,request,*args,**kwargs):
		return HttpResponse('创建Dog')

	def put(self,request,*args,**kwargs):
		return HttpResponse('更新Dog')

	def delete(self,request,*args,**kwargs):
		return HttpResponse('删除Dog')
CATALOG
    FEATURED TAGS
    python 算法 Django 番外工具 组建策划 Vue 数据库 金融 PM