settings.py
MIDDLEWARE = [ 'django.contrib.sessions.middleware.SessionMiddleware', ]
1. 看看SessionMiddleware类 from django.contrib.sessions.middleware import SessionMiddleware
class SessionMiddleware(MiddlewareMixin):
#1.1 def __init__(self, get_response=None): self.get_response = get_response engine = import_module(settings.SESSION_ENGINE) self.SessionStore = engine.SessionStore #2 def process_request(self, request): session_key = request.COOKIES.get(settings.SESSION_COOKIE_NAME) request.session = self.SessionStore(session_key) def process_response(self, request, response): """ If request.session was modified, or if the configuration is to save the session every time, save the changes and set a session cookie or delete the session cookie if the session has been emptied. """ try: accessed = request.session.accessed modified = request.session.modified empty = request.session.is_empty() except AttributeError: pass else: # First check if we need to delete this cookie. # The session should be deleted only if the session is entirely empty if settings.SESSION_COOKIE_NAME in request.COOKIES and empty: response.delete_cookie( settings.SESSION_COOKIE_NAME, path=settings.SESSION_COOKIE_PATH, domain=settings.SESSION_COOKIE_DOMAIN, ) else: if accessed: patch_vary_headers(response, ('Cookie',)) if (modified or settings.SESSION_SAVE_EVERY_REQUEST) and not empty: if request.session.get_expire_at_browser_close(): max_age = None expires = None else: max_age = request.session.get_expiry_age() expires_time = time.time() + max_age expires = cookie_date(expires_time) # Save the session data and refresh the client cookie. # Skip session save for 500 responses, refs #3881. if response.status_code != 500: try: request.session.save() except UpdateError: raise SuspiciousOperation( "The request's session was deleted before the " "request completed. The user may have logged " "out in a concurrent request, for example." ) response.set_cookie( settings.SESSION_COOKIE_NAME, request.session.session_key, max_age=max_age, expires=expires, domain=settings.SESSION_COOKIE_DOMAIN, path=settings.SESSION_COOKIE_PATH, secure=settings.SESSION_COOKIE_SECURE or None, httponly=settings.SESSION_COOKIE_HTTPONLY or None, ) return response
1.1步:每个中间件的类在调用的时候都会先执行init 构造方法
class SessionMiddleware(MiddlewareMixin): def __init__(self, get_response=None): self.get_response = get_response #1.1.1 到配置文件中获取一个类 engine = import_module(settings.SESSION_ENGINE) self.SessionStore = engine.SessionStore
1.1.1步:django自带的settings中没有SESSION_ENGINE这个属性,那就需要去全局的global_settings文件中找
SESSION_ENGINE = 'django.contrib.sessions.backends.db' #这个时候self.SessionStore =db 文件中的 SessionStore类
class SessionStore(SessionBase): """ Implements database session store. """ def __init__(self, session_key=None): super(SessionStore, self).__init__(session_key) @classmethod def get_model_class(cls): # Avoids a circular import and allows importing SessionStore when # django.contrib.sessions is not in INSTALLED_APPS. from django.contrib.sessions.models import Session return Session @cached_property def model(self): return self.get_model_class() def load(self): try: s = self.model.objects.get( session_key=self.session_key, expire_date__gt=timezone.now() ) return self.decode(s.session_data) except (self.model.DoesNotExist, SuspiciousOperation) as e: if isinstance(e, SuspiciousOperation): logger = logging.getLogger('django.security.%s' % e.__class__.__name__) logger.warning(force_text(e)) self._session_key = None return {} def exists(self, session_key): return self.model.objects.filter(session_key=session_key).exists() def create(self): while True: self._session_key = self._get_new_session_key() try: # Save immediately to ensure we have a unique entry in the # database. self.save(must_create=True) except CreateError: # Key wasn't unique. Try again. continue self.modified = True return def create_model_instance(self, data): """ Return a new instance of the session model object, which represents the current session state. Intended to be used for saving the session data to the database. """ return self.model( session_key=self._get_or_create_session_key(), session_data=self.encode(data), expire_date=self.get_expiry_date(), ) def save(self, must_create=False): """ Saves the current session data to the database. If 'must_create' is True, a database error will be raised if the saving operation doesn't create a *new* entry (as opposed to possibly updating an existing entry). """ if self.session_key is None: return self.create() data = self._get_session(no_load=must_create) obj = self.create_model_instance(data) using = router.db_for_write(self.model, instance=obj) try: with transaction.atomic(using=using): obj.save(force_insert=must_create, force_update=not must_create, using=using) except IntegrityError: if must_create: raise CreateError raise except DatabaseError: if not must_create: raise UpdateError raise def delete(self, session_key=None): if session_key is None: if self.session_key is None: return session_key = self.session_key try: self.model.objects.get(session_key=session_key).delete() except self.model.DoesNotExist: pass @classmethod def clear_expired(cls): cls.get_model_class().objects.filter(expire_date__lt=timezone.now()).delete()
SessionStore类
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