django原始碼分析 請求流程

1. 瀏覽器解析輸入的url

2. 查詢url對應的ip位址

3. 通過ip位址訪問我們的伺服器

1.  請求進入wsgi伺服器（我在這裡省略了可能存在的**伺服器，比如nginx）

2.  wsgi伺服器將請求包裝後，傳遞給django應用

3.  django應用根據請求路徑找到相應的處理函式進行處理

4.  處理完成後，django應用將響應返回給wsgi伺服器

5. wsgi伺服器將django應用返回的響應包裝後，返回響應

4. 伺服器返回響應內容，瀏覽器渲染輸出

#wsgi.py檔案

class
wsgihandler(base.basehandler):
request_class =wsgirequest
def__init__(self, *args, **kwargs):
super().
__init__(*args, **kwargs)
self.load_middleware()
def__call__
(self, environ, start_response):
set_script_prefix(get_script_name(environ))
signals.request_started.send(sender=self.__class__, environ=environ)
request =self.request_class(environ)
response =self.get_response(request)
response._handler_class = self.__class__
status = '
%d %s
' %(response.status_code, response.reason_phrase)
response_headers =list(response.items())
for c in
response.cookies.values():
'set-cookie
', c.output(header=''
))) start_response(status, response_headers)
if getattr(response, '
file_to_stream
', none) is
not none and environ.get(''):
response = environ['
'](response.file_to_stream)
return response

# wsgi.py檔案

def

load_middleware(self):
...self._view_middleware =
self._template_response_middleware =
self._exception_middleware =
handler =convert_exception_to_response(self._get_response)
for middleware_path in
reversed(settings.middleware):
middleware =import_string(middleware_path)
try:
mw_instance =middleware(handler)
except
middlewarenotused as exc:
...handler =convert_exception_to_response(mw_instance)
self._middleware_chain = handler

1. 例項化乙個request_class

2. 通過get_response獲取請求，get_response最終會呼叫被中介軟體封裝後的函式 _get_response 

def

_get_response(self, request):
response =none
if hasattr(request, '
urlconf'):
urlconf =request.urlconf
set_urlconf(urlconf)
resolver =get_resolver(urlconf)
else
: resolver =get_resolver()
resolver_match =resolver.resolve(request.path_info)
callback, callback_args, callback_kwargs =resolver_match
request.resolver_match =resolver_match
...if response is
none:
try:
except
exception as e:
response =self.process_exception_by_middleware(e, request)
...return response

下面是這個過程的流程圖

我也以一種函式的形式，寫了一下這個流程

def process_request(request)

try:
# 請求前的中介軟體
response =pre_middleware(request)
ifresponse:
return
response
# 檢視中介軟體
response =view_middleware(request, view_fun)
ifnot response:
try:
# 執行檢視函式
reponses =view_fun(request)
except:
# 異常中介軟體
responser =exception_middleware()
if hasattr(response, '
render'):
# 模板中介軟體
response =template_middleware(response)
try:
response =response.render()
except:
response =exception_middleware()
# 請求後的中介軟體
response =post_middleware(request, response)
except:
response =exception()
return response

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