DRF中的request

1. 前置面向对象知识点

• 直接访问或利用反射

class Foo(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def show(self):
        return 123


obj = Foo("小三", 19)
# obj.name
# obj.age
# obj.show()

v1 = getattr(obj, 'show')
print(v1)

• getattr
  • 当对象.一个不存在的成员时触发

class Foo(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def show(self):
        return 123

    def __getattr__(self, item):
        print("----->", item)
        return 999


obj = Foo("小三", 19)

# 不触发 __getattr
# obj.name
# obj.age
# obj.show()

# 触发 __getattr__ (不存在的成员)
# print(obj.xxx)
v2 = getattr(obj, "xxxx")
print(v2)

• getattribute
  • 只要执行 对象.xxx都会执行__getattribute__
  • 父类object中的__getattribute__的处理机制
    • 对象中有值，返回
    • 对象中无值，报错

class Foo(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def show(self):
        return 123

    def __getattribute__(self, item):
        print("----->", item)
        return 999


obj = Foo("小三", 19)

print(obj.name)
print(obj.age)
print(obj.xxx)

• 类分析

class HttpRequest(object):
    def __init__(self):
        pass

    def v1(self):
        print("v1")

    def v2(self):
        print("v2")


class Request(object):
    def __init__(self, req, xx):
        self._request = req
        self.xx = xx


req = HttpRequest()
req.v1()
req.v2()

request = Request(req, 111)
request._request.v1()
request._request.v2()

class HttpRequest(object):
    def __init__(self):
        pass

    def v1(self):
        print("v1")

    def v2(self):
        print("v2")


class Request(object):
    def __init__(self, req, xx):
        self._request = req
        self.xx = xx

    # 对象中无的成员，会触发
    def __getattr__(self, attr):
        # attr="v1"
        try:
            return getattr(self._request, attr)  # self._request.v1
        except AttributeError:
            return self.__getattribute__(attr)


req = HttpRequest()

request = Request(req, 111)
request.v1()

• request的简单实现原理

class HttpRequest(object):
    def __init__(self):
        pass

    def method(self):
        print("v1")

    def path_info(self):
        print("v2")


class DrfRequest(object):
    def __init__(self, req, xx):
        self._request = req
        self.xx = xx

    def __getattr__(self, attr):
        try:
            return getattr(self._request, attr)
        except AttributeError:
            return self.__getattribute__(attr)


request = HttpRequest()
request = DrfRequest(request, 123123)

# 普通写法
request._request.method
# 利用__getattr__和__getattribute__
request.method
request.path_info
# 报错
request.uuuu

2. 参数

• 测试代码

from django.contrib import admin
from django.urls import path, re_path
from api import views

urlpatterns = [
    # path('admin/', admin.site.urls),
    # path('users/<str:version>/<int:pid>/', views.UserView.as_view()),
    # re_path('users/(\w+)/(\d+)/', views.UserView.as_view()),
    re_path('users/(?P<version>\w+)/(?P<pid>\d+)/', views.UserView.as_view()),
]

from rest_framework.views import APIView
from rest_framework.response import Response


class UserView(APIView):
    def get(self, request, version, pid):
        print(version, pid)
        print(self.kwargs)
        print(self.args)
        return Response("...")

3. 源码分析

• 流程梳理-文字版

注意：下列调用方法的找寻路线遵循先UserView类，后APIView类，最后是View类，就不再详细赘述找寻过程

首先入口是路由中调用UserView类的as_View()方法，找到APIView类的as_view()方法，又调用View类的as_view()方法
View类的as_view()方法调用APIView类的dispatch方法
dispatch()方法调用initialize_request()方法，将django的request传给drf的Request类进行封装，self._request = request，并且定义了__getattr__方法，用于在drf的request中调用原生django的request
此时initialize_request()方法调用完毕，回到dispatch()方法
dispatch()获取请求方法，并调用，将结果一步步返回

• 源代码分析-精简版

class APIView(View):
    def as_view(cls, **initkwargs):
        view = super().as_view(**initkwargs)
        return csrf_exempt(view)

    def initialize_request(self, request, *args, **kwargs):
        parser_context = self.get_parser_context(request)

        return Request(
            request,
            parsers=self.get_parsers(),
            authenticators=self.get_authenticators(),
            negotiator=self.get_content_negotiator(),
            parser_context=parser_context
        )

    def dispatch(self, request, *args, **kwargs):
        self.args = args
        self.kwargs = kwargs
        # request还是django中的request
        request = self.initialize_request(request, *args, **kwargs)
        # 此时的request时drf的request，request._request就是原生django的request
        # request._request.method
        # request.method  # __getattr__
        self.request = request
        self.headers = self.default_response_headers

        if request.method.lower() in self.http_method_names:
            # 获取get/post/put等方法
            handler = getattr(self, request.method.lower(),self.http_method_not_allowed)
        # 调用get/post等方法(UserView中)
        response = handler(request, *args, **kwargs)

        self.response = self.finalize_response(request, response, *args, **kwargs)
        return self.response


class View:
    def as_view(cls, **initkwargs):
        def view(request, *args, **kwargs):
            return self.dispatch(request, *args, **kwargs)

        return view


class Request:
    def __init__(self, request, parsers=None, authenticators=None,
                 negotiator=None, parser_context=None):
        self._request = request

    def __getattr__(self, attr):

        try:
            return getattr(self._request, attr)
        except AttributeError:
            return self.__getattribute__(attr)
        
        
class UserView(APIView):
    def get(self, request, version, pid):
        print(version, pid)
        print(self.kwargs)
        print(self.args)
        return Response("...")

4. request对象

drf中的request其实是对请求的再次封装，其目的就是在原来的request对象基础中再进行封装一些drf中需要用到的值

• 测试代码

from django.contrib import admin
from django.urls import path, re_path
from api import views

urlpatterns = [
    # path('admin/', admin.site.urls),
    # path('users/<str:version>/<int:pid>/', views.UserView.as_view()),
    # re_path('users/(\w+)/(\d+)/', views.UserView.as_view()),
    re_path('users/(?P<version>\w+)/(?P<pid>\d+)/', views.UserView.as_view()),
]

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.request import Request


class UserView(APIView):
    def get(self, request, version, pid):
        # drf的request对象
        print(request.query_params)
        print(request.data)
        print(request.auth)
        print(request.user)

        # django的request对象
        print(request.GET)
        print(request.method)
        print(request.path_info)
        return Response("...")