request请求生命周期

Posted 2021-03-11 randysun

request请求生命周期

一、request请求分析

1.1. request数据请求

# views.py
from rest_framework.views import APIView
from rest_framework.response import Response
from django.http.request import QueryDict
class BookAPIView(APIView):

    def get(self, request, *args, **kwargs):
        print(request._request.GET)  # 原生wigs中值
        print(request.GET) # 二次封装的值
        print(request.META) # 所有get请求信息
        print(request.META.get("HTTP_AUTH")) # 前台发来的头都会大写并加上HTTP
        print(request.query_params) # 所有url数据
        
        print(request.POST) # get请求不能获取Post请求数据

        return Response('get ok')

    def post(self, request, *args, **kwargs):
        print(request._request.POST)  # 原生wigs中值
        print(request.POST) # 二次封装的值
        print(request.data) # 所有post请求数据
        print(request._request) # url数据包<WSGIRequest: POST '/books/?age=123'>
        print(request.GET) # POST请求可以Post请求数据
            
         # QueryDict转为
        print(request.query_params.dict())
        if isinstance(request.data, QueryDict):
            print(request.data.dict())

        return Response('post ok')
    
    
    
# urls.py
from . import views
urlpatterns = [
    url(r'^books/$', views.BookAPIView.as_view()),
]

总结：

1. drf中的request是在wsgi的request基础上进行再一次封装
2. 将wsgi的request作为drf的request的一个属性, _request
3. drf中的request对wsgi中的request做完全兼容，新的可以直接获取wsgi中的数据
4. drf中的request对数据解析更规范化,所有的拼接参数(url?age=18)都解析到了query_params中，所有数据报数据都解析到data中
5. query_params和data属于QueryDict类型,可以通过.dict()转化为字典类型

二、request请求源码分析

# 1. 2. urls.py
from . import views
urlpatterns = [
    url(r'^books/$', views.BookAPIView.as_view()),
]

#3.调用drf中的as_view
@classmethod
def as_view(cls, **initkwargs):     # cls 为 views.BookAPIView类
    ...
    view = super().as_view(**initkwargs) # as_view原生的as_view,super() 为 view
    view.cls = cls
    view.initkwargs = initkwargs

    return csrf_exempt(view)
# 4.进入drf中dispatch 
def dispatch(self, request, *args, **kwargs):   # self为views.BookAPIView类
    self.args = args  
    self.kwargs = kwargs
    # 对原生request进行了二次封装
    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
                
# 4.1 返回封装的request对象
def initialize_request(self, request, *args, **kwargs):
    """
        Returns the initial request object.
        """
    parser_context = self.get_parser_context(request) # 解析

    return Request(
        request, # 二次封装
        parsers=self.get_parsers(),
        authenticators=self.get_authenticators(),
        negotiator=self.get_content_negotiator(),
        parser_context=parser_context
    )
# 5.Request类创建 self._request = request自己的属性
 def __init__(self, request, parsers=None, authenticators=None,
                 negotiator=None, parser_context=None):
        assert isinstance(request, HttpRequest), (
           
            .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
        
#6.如何实现获取wgis中的属性
def __getattr__(self, attr):   
    """
        If an attribute does not exist on this instance, then we also attempt
        to proxy it to the underlying HttpRequest object.
        """
    try:
        return getattr(self._request, attr)
    except AttributeError:
        return self.__getattribute__(attr)

1. 导入drf中的APIView并创建类继承它，在配置url: url(r‘^books/$‘, views.BookAPIView.as_view()),

2. 当项目启动时会执行drf中的as_view()方法，返回view方法(局部禁用了csrf认证)， url：url(r‘^books/$‘, views.BookAPIView.view

3. 浏览器发送请求来时则会执行url中view函数，在执行view中返回的是 self.dispatch(request, *args, **kwargs), dispatch是drf中的dispatch, 不是wsgi中原生的dispatch

4. 进入drf中的dispatch首先会对原生的request进行二次封装：request = self.initialize_request(request, *args, **kwargs),在initialize_request方法中返回了一个request实例对象

5. 进入request.py中的Request方法中就会发现在初始化方法中将wsgi方法的request变为了自己的一个属性： ‘self._request = request‘

6. request通过反射的方法获取wsgi中request属性，当request.获取属性先到 _request中查找，没有则查自己本身的

   #6.如何实现获取wgis中的属性
   def __getattr__(self, attr):   
       """
           If an attribute does not exist on this instance, then we also attempt
           to proxy it to the underlying HttpRequest object.
           """
       try:
           return getattr(self._request, attr)
       except AttributeError:
           return self.__getattribute__(attr)

7. 核心
   • 走drf的Request初始化方法__init__：self._request = request
   • drf的Request的getter方法__getattr__：先从self._request反射取属性，没取到再从drf的request中取
   • request除了可以访问原wsgi协议的request所有内容，还可以访问 query_params、data