python - Flask源碼異常處理問題

問題描述

Flask version: 0.3

我事先在views.py里面定義了如下的異常處理方法：

@app.errorhandler(404)def page_not_found(): return 'this page is not found.', 404 @app.errorhandler(500)def page_error(): return 'this page is error.', 500 #:: 這兩個異常處理方法都是錯誤的，因為沒有加參數。

先貼幾段源碼

#:: 片段1def wsgi_app(self, environ, start_response): with self.request_context(environ):try: rv = self.preprocess_request() if rv is None:rv = self.dispatch_request() response = self.make_response(rv) response = self.process_response(response)except Exception, e: response = self.make_response(self.handle_exception(e))return response(environ, start_response)#:: 片段2def dispatch_request(self): req = _request_ctx_stack.top.request try:if req.routing_exception is not None: raise req.routing_exception #:: 拋出異常return self.view_functions[req.endpoint](**req.view_args) except HTTPException, e:return self.handle_http_exception(e)#:: 片段3class _RequestContext(object): def __init__(self, app, environ):self.app = appself.url_adapter = app.url_map.bind_to_environ(environ)self.request = app.request_class(environ)self.session = app.open_session(self.request)if self.session is None: self.session = _NullSession()self.g = _RequestGlobals()self.flashes = Nonetry: self.request.endpoint, self.request.view_args = self.url_adapter.match() #:: 不匹配except HTTPException, e: print e.code, e.description self.request.routing_exception = e #:: 片段4def handle_exception(self, e): handler = self.error_handlers.get(500) if self.debug:raise self.logger.error('hello') self.logger.exception(’Exception on %s [%s]’ % (request.path,request.method )) if handler is None:return InternalServerError() return handler(e) #:: handler不為None，之前定義了500的錯誤處理

然后我在瀏覽器輸入了一個不存在的路由http://localhost:5000/test，想看Flask如何異常處理。

請求過來之后會先執行片段1， 然后代碼走到片段3請求上下文，片段3中self.url_adapter.match()拋出HTTPException異常被捕獲。然后執行到片段2，然后拋出異常被片段1捕獲到執行片段4，最后會執行到handler(e)這條語句。

我的問題來了，因為我定義的500的錯誤處理里面，沒有加參數，導致這條語句執行失敗。

報了如下錯誤：

Traceback (most recent call last): File '/Users/virtualenvs/full-stack/lib/python2.7/site-packages/werkzeug/serving.py', line 180, in run_wsgi execute(self.server.app) File '/Users/virtualenvs/full-stack/lib/python2.7/site-packages/werkzeug/serving.py', line 168, in execute application_iter = app(environ, start_response) File '/Users/virtualenvs/full-stack/flask0.3/examples/flaskr/flask.py', line 1435, in __call__ return self.wsgi_app(environ, start_response) File '/Users/virtualenvs/full-stack/lib/python2.7/site-packages/werkzeug/wsgi.py', line 591, in __call__ return self.app(environ, start_response) File '/Users/virtualenvs/full-stack/flask0.3/examples/flaskr/flask.py', line 1382, in wsgi_app response = self.make_response(self.handle_exception(e)) File '/Users/virtualenvs/full-stack/flask0.3/examples/flaskr/flask.py', line 1266, in handle_exception return handler(e)TypeError: page_error() takes no arguments (1 given)

從Traceback當中能看出最后也是這句的錯誤。然而瀏覽器還是返回了500的頁面，返回的內容是Werkzeug自定義的頁面內容。

Internal Server ErrorThe server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.

既然程序都已經執行錯誤了，那為什么還能夠返回HTTP Response呢？謝謝:-)

問題解答

報錯信息提示很清楚 File '/Users/virtualenvs/full-stack/flask0.3/examples/flaskr/flask.py', line 1266, in handle_exception

return handler(e)

TypeError: page_error() takes no arguments (1 given)

page_error() 不需要參數，你傳遞了一個參數。