執行流程原始碼分析

成风人發表於2024-09-27
原始碼
首先 
urlpatterns = [
    url('view/', api_view.as_view()),
]

class APIView(View):
    @classmethod
    def as_view(cls, **initkwargs):
        if isinstance(getattr(cls, 'queryset', None), models.query.QuerySet):
            def force_evaluation():
                raise RuntimeError(
                    'Do not evaluate the `.queryset` attribute directly, '
                    'as the result will be cached and reused between requests. '
                    'Use `.all()` or call `.get_queryset()` instead.'
                )
            cls.queryset._fetch_all = force_evaluation

        view = super().as_view(**initkwargs)
        view.cls = cls
        view.initkwargs = initkwargs
        return csrf_exempt(view)
返回的是解除了csrf_exempt(view), 下一步找view APIView類裡沒有, 就找父類的view
找到view函式 



class View:
    def view(request, *args, **kwargs):
        self = cls(**initkwargs)
        self.setup(request, *args, **kwargs)
        if not hasattr(self, 'request'):
            raise AttributeError(
                "%s instance has no 'request' attribute. Did you override "
                "setup() and forget to call super()?" % cls.__name__
            )
        return self.dispatch(request, *args, **kwargs)

    view.view_class = cls
    view.view_initkwargs = initkwargs

    update_wrapper(view, cls, updated=())

    update_wrapper(view, cls.dispatch, assigned=())
    return view
返回了 return self.dispatch(request, *args, **kwargs), 就去找dispatch, 自己類裡沒有,在class APIView(View)裡找到
找到dispatch函式 
class APIView(View):
    def dispatch(self, request, *args, **kwargs):
        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)

            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

這裡面主要看 if request.method.lower() in self.http_method_names:
handler = getattr(self, request.method.lower(),
self.http_method_not_allowed)
意思是，請求過來的方式。並且轉成小寫字母，然後在後面加括號並且執行。
最後，打包到return self.response並且返回。

下一步分析request引數，和傳過去的引數。

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