Django应用程序入口WSGIHandler源码解析

# Python dotted path to the WSGI application used by Django's runserver.WSGI_APPLICATION = 'tomato.wsgi.application'

import os os.environ.setdefault("DJANGO_SETTINGS_MODULE", "tomato.settings")from django.core.wsgi import get_wsgi_applicationapplication = get_wsgi_application()

from django.core.handlers.wsgi import WSGIHandlerdef get_wsgi_application():  """  The public interface to Django's WSGI support. Should return a WSGI  callable.   Allows us to avoid making django.core.handlers.WSGIHandler public API, in  case the internal WSGI implementation changes or moves in the future.   """  """  # 继承, 但只实现了 __call__ 方法, 方便使用  class WSGIHandler(base.BaseHandler):  """  return WSGIHandler()

# 继承, 但只实现了 __call__ 方法, 方便使用class WSGIHandler(base.BaseHandler):  initLock = Lock()   # 关于此, 日后展开, 可以将其视为一个代表 http 请求的类  request_class = WSGIRequest   # WSGIHandler 也可以作为函数来调用  def __call__(self, environ, start_response):    # Set up middleware if needed. We couldn't do this earlier, because    # settings weren't available.     # 这里的检测: 因为 self._request_middleware 是最后才设定的, 所以如果为空,    # 很可能是因为 self.load_middleware() 没有调用成功.    if self._request_middleware is None:      with self.initLock:        try:          # Check that middleware is still uninitialised.          if self._request_middleware is None:            因为 load_middleware() 可能没有调用, 调用一次.            self.load_middleware()        except:          # Unload whatever middleware we got          self._request_middleware = None          raise     set_script_prefix(base.get_script_name(environ))    signls.request_started.send(sender=self.__class__) # __class__ 代表自己的类     try:      # 实例化 request_class = WSGIRequest, 将在日后文章中展开, 可以将其视为一个代表 http 请求的类      request = self.request_class(environ)     except UnicodeDecodeError:      logger.warning('Bad Request (UnicodeDecodeError)',        exc_info=sys.exc_info(),        extra={          'status_code': 400,        }      )      response = http.HttpResponseBadRequest()    else:      # 调用 self.get_response(), 将会返回一个相应对象 response<br>      ############# 关键的操作, self.response() 可以获取响应数据.           response = self.get_response(request)     # 将 self 挂钩到 response 对象    response._handler_class = self.__class__     try:      status_text = STATUS_CODE_TEXT[response.status_code]    except KeyError:      status_text = 'UNKNOWN STATUS CODE'     # 状态码    status = '%s %s' % (response.status_code, status_text)     response_headers = [(str(k), str(v)) for k, v in response.items()]     # 对于每个一个 cookie, 都在 header 中设置: Set-cookie xxx=yyy    for c in response.cookies.values():      response_headers.append((str('Set-Cookie'), str(c.output(header=''))))     # start_response() 操作已经在上节中介绍了    start_response(force_str(status), response_headers)     # 成功返回相应对象    return response