在tornado.web.RequestHandler类中的初始构造方法中：
class RequestHandler(object): """Base class for HTTP request handlers. Subclasses must define at least one of the methods defined in the "Entry points" section below. """ SUPPORTED_METHODS = ("GET", "HEAD", "POST", "DELETE", "PATCH", "PUT", "OPTIONS") _template_loaders = {} # type: typing.Dict[str, template.BaseLoader] _template_loader_lock = threading.Lock() _remove_control_chars_regex = re.compile(r"[x00-x08x0e-x1f]") def __init__(self, application, request, **kwargs): super(RequestHandler, self).__init__() self.application = application self.request = request self._headers_written = False self._finished = False self._auto_finish = True self._transforms = None # will be set in _execute self._prepared_future = None self._headers = None # type: httputil.HTTPHeaders self.path_args = None self.path_kwargs = None self.ui = ObjectDict((n, self._ui_method(m)) for n, m in application.ui_methods.items()) # UIModules are available as both `modules` and `_tt_modules` in the # template namespace. Historically only `modules` was available # but could be clobbered by user additions to the namespace. # The template {% module %} directive looks in `_tt_modules` to avoid # possible conflicts. self.ui["_tt_modules"] = _UIModuleNamespace(self, application.ui_modules) self.ui["modules"] = self.ui["_tt_modules"] self.clear() self.request.connection.set_close_callback(self.on_connection_close) self.initialize(**kwargs)
尾部自动调用tornado为用户预留的initialize方法（未实现，是由用户调用来实现）
def initialize(self): """Hook for subclass initialization. Called for each request. A dictionary passed as the third argument of a url spec will be supplied as keyword arguments to initialize(). Example:: class ProfileHandler(RequestHandler): def initialize(self, database): self.database = database def get(self, username): ... app = Application([ (r'/user/(.*)', ProfileHandler, dict(database=database)), ]) """ pass
所以对于之前的session类的使用上可以用到钩子，就像php中的公共控制类中构造方法中调用某些函数，会在每个控制器执行时去执行这些函数，减少在代码中的复用。
前面session类的改进
class BaseRequestHandler(tornado.web.RequestHandler): #tornado预留钩子函数 def initialize(self): self.session=Session(self) class IndexHandler(BaseRequestHandler): def get(self): if self.get_argument('u',None) in ['asd','zxc']: #在这里有个bug,当程序两次设置值时，逻辑相同，但是由于只发送了一次请求，获取了第一次的py_session #在相同逻辑代码处理下random_str=self.handler.get_cookie('py_session') #每次都是不正确的，都需要重新创建一个标识符 #但是后面的刷新过程中由于修改了客户区的py_session,所以可以正常进行操作，但是第一次产生的py_session的依旧存在服务端 self.session.set_value('is_login',True) self.session.set_value('name',self.get_argument('u')) #self.get_secure_cookie() #The decoded cookie value is returned as a byte string (unlike #`get_cookie`). else: self.write("请登录")