Python 官方文档：入门教程 => 点击学习
目录一、Django运行顺序1.启动1.1 命令行启动(测试服务器)2.监听2.1 runserver(测试服务器)3.中间件的执行本文只算是本人片面之言（当然也会借鉴网络上公开资料
本文只算是本人片面之言（当然也会借鉴网络上公开资料），而且技术含量比较低，内容质量也一般，大家仅限参考即可
如果对本文看不太懂，请先阅读后面文章，等都差不多看完再回顾来看
命令行结论：其在第二步utility.execute()函数会根据命令行参数，分发给不同的类进行处理
在manange.py里面execute_from_command_line(sys.argv)进入关键代码
def main():
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'testDjango.settings')
try:
from django.core.management import execute_from_command_line
except ImportError as exc:
---
execute_from_command_line(sys.argv)2.execute_from_command_line函数里面其实例化 ManagementUtility类然后执行utility.execute()函数 [
2.1. 此函数是专门用来分析参数的，例如python manage.py runserver、Python manage.py help
2.2 其会通过分析额外添加的参数选择要使用的类或者函数，类或者函数对应着django\core\management\commands里面的类
def execute_from_command_line(argv=None):
utility = ManagementUtility(argv)
utility.execute()3.从self.fetch_command(subcommand).run_from_argv(self.argv)[约第413行]
3.1 self.fetch_command(subcommand)，这个函数返回了runserver.Command对象（可以自行深入查看），之后执行该Command父类里面的run_from_argv函数
def execute(self):
---
if subcommand == 'help':
---
elif subcommand == 'version' or self.argv[1:] == ['--version']:
sys.stdout.write(django.get_version() + '\n')
elif self.argv[1:] in (['--help'], ['-h']):
sys.stdout.write(self.main_help_text() + '\n')
else:
self.fetch_command(subcommand).run_from_argv(self.argv)4.从run_from_argv函数self.execute(*args, **cmd_options)进入
4.1 当前类也有这个execute函数，但是由于继承关系（此时的self也指向Command类），子类如果已经存在该函数会覆盖执行，execute是在子类 Command类中（之后由于super还会到父类里面）[约第354行]
def run_from_argv(self, argv):
self._called_from_command_line = True
parser = self.create_parser(argv[0], argv[1])
options = parser.parse_args(argv[2:])
cmd_options = vars(options)
args = cmd_options.pop('args', ())
handle_default_options(options)
try:
self.execute(*args, **cmd_options)
except CommandError as e:
---5.execute函数执行output = self.handle(*args, **options)[约第398行]跳进子类runserver.Command类的handle函数
5.1 此时位于Command类的父类里面的execute，因为super().execute(*args, **options) #继承下来父类
def handle(self, *args, **options):
if not settings.DEBUG and not settings.ALLOWED_HOSTS:
raise CommandError('You must set settings.ALLOWED_HOSTS if DEBUG is False.')
self.use_ipv6 = options['use_ipv6']
if self.use_ipv6 and not Socket.has_ipv6:
raise CommandError('Your Python does not support IPv6.')
self._raw_ipv6 = False
if not options['addrport']:
---
else:
---
if not self.addr:
self.addr = self.default_addr_ipv6 if self.use_ipv6 else self.default_addr
self._raw_ipv6 = self.use_ipv6
self.run(**options)
6.handle 函数最后一行，从 self.run(**options) 进入
def run(self, **options):
use_reloader = options['use_reloader']
if use_reloader:
autoreload.run_with_reloader(self.inner_run, **options)
else:
self.inner_run(None, **options)
7.从def inner_run(self, *args, \*\*options)再执行run函数
def inner_run(self, *args, **options):
---
try:
handler = self.get_handler(*args, **options)
run(self.addr, int(self.port), handler,
ipv6=self.use_ipv6, threading=threading, server_cls=self.server_cls)
except OSError as e:
---
8.最后启动服务，此时跳到django.core.servers.basehttp.py的run函数
8.1 Httpd_cls = type('WSGIServer', (socketserver.ThreadingMixIn, server_cls), {}) 这一步特别重要，其涉及到较长的继承关系，2.监听-4.1这一环节会介绍到
def run(addr, port, wsgi_handler, ipv6=False, threading=False, server_cls=WSGIServer):
server_address = (addr, port)
if threading:
httpd_cls = type('WSGIServer', (socketserver.ThreadingMixIn, server_cls), {})
else:
httpd_cls = server_cls
httpd = httpd_cls(server_address, WSGIRequestHandler, ipv6=ipv6)
if threading:
httpd.daemon_threads = True
httpd.set_app(wsgi_handler)
httpd.serve_forever()总结流程：
解释：WSGI开启后，不间断的监听外界的请求
快速阅读：下面写的比较麻烦，最快了解监听和到中间件前的经过就是去读 1 、12.1 和 13
1.runserver成功开启后，关键的一步是httpd.serve_forever()，其使得进入监听即一个死循环
def run(addr, port, wsgi_handler, ipv6=False, threading=False, server_cls=WSGIServer):
---
httpd.set_app(wsgi_handler)
httpd.serve_forever()
2.在serve_forever()函数里面执行，当ready有值时，表示有请求发来，然后进入self._handle_request_noblock()
def serve_forever(self, poll_interval=0.5):
self.__is_shut_down.clear()
try:
with _ServerSelector() as selector:
selector.register(self, selectors.EVENT_READ)
while not self.__shutdown_request:
ready = selector.select(poll_interval)
if self.__shutdown_request:
break
if ready:
self._handle_request_noblock()
self.service_actions()
---3.从self._handle_request_noblock()正常请求将进入self.process_request(request, client_address)
def _handle_request_noblock(self):
try:
request, client_address = self.get_request()
except OSError:
return
if self.verify_request(request, client_address):
try:
self.process_request(request, client_address)
except Exception:
self.handle_error(request, client_address)
self.shutdown_request(request)
except:
self.shutdown_request(request)
raise
else:
self.shutdown_request(request)4.从self.process_request(request, client_address)进入来到了ThreadingMixIn.process_request
4.1 此时，如果没有搞清楚此时的self是谁，就搞不明白为什么进入到ThreadingMixIn.process_request，而不是其它的process_request，这时候就关联到上面提到的httpd_cls = type('WSGIServer', (socketserver.ThreadingMixIn, server_cls), {})
4.2 type的用法是动态的创建类，此时httpd_cls 是一个新类，里面分别继承了ThreadingMixIn和server_cls对应得WSGIServer，这时就不难理解为什么找的是ThreadingMixIn.process_request
def process_request(self, request, client_address):
"""Start a new thread to process the request."""
t = threading.Thread(target = self.process_request_thread,
args = (request, client_address))
t.daemon = self.daemon_threads
if not t.daemon and self.block_on_close:
if self._threads is None:
self._threads = []
self._threads.append(t)
t.start()
5.在def process_request(self, request, client_address)里面的t = threading.Thread(target = self.process_request_thread,args = (request, client_address))实际调用了self.process_request_thread，但是等t.start()才会真正执行
def process_request_thread(self, request, client_address):
"""Same as in BaseServer but as a thread.
In addition, exception handling is done here.
"""
try:
self.finish_request(request, client_address)
except Exception:
self.handle_error(request, client_address)
finally:
self.shutdown_request(request)
6.从def process_request_thread(self, request, client_address)进入，self.finish_request(request, client_address)，继续完成请求
6.1 这时候又需要回顾之前的代码，因为self.RequestHandlerClass不是已经有的类，而是初始化的时候赋值，其值变为了某个类
6.2 这个过程就在1.启动-8里面的httpd = httpd_cls(server_address, WSGIRequestHandler, ipv6=ipv6)，此时的httpd_cls是type动态创建的，继承了ThreadingMixIn和server_cls对应得WSGIServer，实例化时会执行def __init__方法，其关键执行了self.RequestHandlerClass = RequestHandlerClass
class BaseServer:
timeout = None
def __init__(self, server_address, RequestHandlerClass):
"""Constructor. May be extended, do not override."""
self.server_address = server_address
self.RequestHandlerClass = RequestHandlerClass
self.__is_shut_down = threading.Event()
self.__shutdown_request = False
def finish_request(self, request, client_address):
self.RequestHandlerClass(request, client_address, self)
# self.RequestHandlerClass等同于self.WSGIRequestHandler
7.从self.RequestHandlerClass(request, client_address, self)，即去WSGIRequestHandler类里面初始化，根据一层层继承关系，只要最老类BaseRequestHandler有初始化方法
class BaseRequestHandler:
def __init__(self, request, client_address, server):
self.request = request
self.client_address = client_address
self.server = server
self.setup()
try:
self.handle()
finally:
self.finish()
从def __init__(self, request, client_address, server):进入self.handle()
8.1 此时的self.handle()，根据继承关系，其就在最小子类WSGIRequestHandler里面
def handle(self):
self.close_connection = True
self.handle_one_request()
while not self.close_connection:
self.handle_one_request()
try:
self.connection.shutdown(socket.SHUT_WR)
except (AttributeError, OSError):
pass
9.从def handle(self)进入self.handle_one_request()
def handle_one_request(self):
"""Copy of WSGIRequestHandler.handle() but with different ServerHandler"""
self.raw_requestline = self.rfile.readline(65537)
if len(self.raw_requestline) > 65536:
self.requestline = ''
self.request_version = ''
self.command = ''
self.send_error(414)
return
if not self.parse_request(): # An error code has been sent, just exit
return
handler = ServerHandler(
self.rfile, self.wfile, self.get_stderr(), self.get_environ()
)
handler.request_handler = self # backpointer for logging & connection closing
handler.run(self.server.get_app())
10.从def handle_one_request(self)进入handler.run(self.server.get_app())
10.1 注意此时handler为ServerHandler实例化对象，run方法存在它的最大父类BaseHandler里面
10.2 此时handler.run(self.server.get_app())执行了self.server.get_app()，其返回django.contrib.staticfiles.handlers.StaticFilesHandler，handler.run把其当参数传递了过去
def run(self, application):
try:
self.setup_environ()
self.result = application(self.environ, self.start_response)
self.finish_response()
except (ConnectionAbortedError, BrokenPipeError, ConnectionResetError):
return
except:
---
11.从def run(self, application)进入self.result = application(self.environ, self.start_response)，其中application是django.contrib.staticfiles.handlers.StaticFilesHandler
11.1 其中self.application已经初始化了是WSGIHandler
class StaticFilesHandler(StaticFilesHandlerMixin, WSGIHandler):
def __init__(self, application):
self.application = application
self.base_url = urlparse(self.get_base_url())
super().__init__()
def __call__(self, environ, start_response):
if not self._should_handle(get_path_info(environ)):
return self.application(environ, start_response)
return super().__call__(environ, start_response)
12.进入后执行def __call__(self, environ, start_response)方法，进入return self.application(environ, start_response)，此时self.application已经初始化了是WSGIHandler
12.1 request = self.request_class(environ)获取到用户请求的url后面就开始配置runserver启动时候加载的url； response = self.get_response(request)获取用户url对应的响应准备开始往视图转
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)
---13.进入response = self.get_response(request)，结束，再下一步就要开始中间件的进行
def get_response(self, request):
set_urlconf(settings.ROOT_URLCONF)
response = self._middleware_chain(request)
response._resource_closers.append(request.close)
if response.status_code >= 400:
log_response(
'%s: %s', response.reason_phrase, request.path,
response=response,
request=request,
)
return response解释：中间件的执行需要联系着上面运行过程，这个过程是一个递归的过程，下面介绍的五个函数是中间件命名规则对应得内容
1.递归的进入阶段：循环进行下面的代码（此代码位置django\core\handlers\exception.py）
1.1 此处出现process_request()和process_response()
@wraps(get_response)
def inner(request):
try:
response = get_response(request) # 此进入循环
except Exception as exc:
response = response_for_exception(request, exc)
return response
return inner def __call__(self, request):
# Exit out to async mode, if needed
if asyncio.iscoroutinefunction(self.get_response):
return self.__acall__(request)
response = None
if hasattr(self, 'process_request'):
response = self.process_request(request) # 进行中间件的process_request步骤
response = response or self.get_response(request) # 此进入循环
if hasattr(self, 'process_response'):
response = self.process_response(request, response) # 此是递归后执行的
return response
2.递归的结束准备回传：进行下面的代码（此代码位置django\core\handlers\base.py）
2.1 此处出现process_view()、process_template_response()和process_exception()
进入视图的关键函数：
def _get_response(self, request):
response = None
callback, callback_args, callback_kwargs = self.resolve_request(request)
for middleware_method in self._view_middleware:
response = middleware_method(request, callback, callback_args, callback_kwargs)
if response:
break
if response is None:
wrapped_callback = self.make_view_atomic(callback) # 找到视图函数
# If it is an asynchronous view, run it in a subthread.
if asyncio.iscoroutinefunction(wrapped_callback):
wrapped_callback = async_to_sync(wrapped_callback)
try:
response = wrapped_callback(request, *callback_args, **callback_kwargs)
except Exception as e:
response = self.process_exception_by_middleware(e, request)
if response is None:
raise
self.check_response(response, callback)
if hasattr(response, 'render') and callable(response.render):
for middleware_method in self._template_response_middleware:
response = middleware_method(request, response)
self.check_response(
response,
middleware_method,
name='%s.process_template_response' % (
middleware_method.__self__.__class__.__name__,
)
)
try:
response = response.render()
except Exception as e:
response = self.process_exception_by_middleware(e, request)
if response is None:
raise
return response
3.递归的结束回传：循环进行下面的代码
@wraps(get_response)
def inner(request):
try:
response = get_response(request) # 此进入循环
except Exception as exc:
response = response_for_exception(request, exc)
return response
return inner
def __call__(self, request):
# Exit out to async mode, if needed
if asyncio.iscoroutinefunction(self.get_response):
return self.__acall__(request)
response = None
if hasattr(self, 'process_request'):
response = self.process_request(request)
response = response or self.get_response(request) # 此进入循环
if hasattr(self, 'process_response'):
response = self.process_response(request, response) # 进行中间件的process_response步骤
return response
到此这篇关于Python Django源码运行过程的文章就介绍到这了,更多相关Python Django源码运行内容请搜索编程网以前的文章或继续浏览下面的相关文章希望大家以后多多支持编程网！
--结束END--
本文标题: Python Django源码运行过程解析
本文链接: https://www.lsjlt.com/news/120121.html(转载时请注明来源链接)
有问题或投稿请发送至: 邮箱/279061341@qq.com QQ/279061341
下载Word文档到电脑，方便收藏和打印～
2024-03-01
2024-03-01
2024-03-01
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
2024-02-29
回答
回答
回答
回答
回答
回答
回答
回答
回答
回答
官方手机版
微信公众号
商务合作
0