python - Flask源码异常处理问题

问题描述

Flask version: 0.3

我事先在views.py里面定义了如下的异常处理方法：

@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 #:: 这两个异常处理方法都是错误的，因为没有加参数。

先贴几段源码

#:: 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 #:: 抛出异常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不为None，之前定义了500的错误处理

然后我在浏览器输入了一个不存在的路由http://localhost:5000/test，想看Flask如何异常处理。

请求过来之后会先执行片段1， 然后代码走到片段3请求上下文，片段3中self.url_adapter.match()抛出HTTPException异常被捕获。然后执行到片段2，然后抛出异常被片段1捕获到执行片段4，最后会执行到handler(e)这条语句。

我的问题来了，因为我定义的500的错误处理里面，没有加参数，导致这条语句执行失败。

报了如下错误：

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)

从Traceback当中能看出最后也是这句的错误。然而浏览器还是返回了500的页面，返回的内容是Werkzeug自定义的页面内容。

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.

既然程序都已经执行错误了，那为什么还能够返回HTTP Response呢？谢谢:-)

问题解答

报错信息提示很清楚 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() 不需要参数，你传递了一个参数。