python - Python 中的异常处理(webapp2、Google App Engine)

Question

我尝试使用建议的函数来处理异常:

http://webapp-improved.appspot.com/guide/exceptions.html

在 main.py 中:

def handle_404(request, response, exception):
        logging.exception(exception)
        response.write('404 Error')
        response.set_status(404)

def handle_500(request, response, exception):
    logging.exception(exception)
    response.write('A server error occurred!')
    response.set_status(500)

class AdminPage(webapp2.RequestHandler):
    def get(self):
    ...
    admin_id = admin.user_id()
    queues = httpRequests.get_queues(admin_id)

app = webapp2.WSGIApplication(...)

app.error_handlers[404] = handle_404
app.error_handlers[500] = handle_500

httpRequests.py中的函数:

def get_queues(admin_id):

    url = "http://localhost:8080/api/" + admin_id + "/queues"
    result = urlfetch.fetch(url)

    if (result.status_code == 200):
        received_data = json.loads(result.content)
        return received_data

API 中调用的函数:

class Queues(webapp2.RequestHandler): 
    def get(self, admin_id): 
        queues = queues(admin_id)
        if queues == []:
            self.abort(404)
        else:
            self.response.write(json.dumps(queues))

我卡在了 httpRequests.py 的 get_queues 处。如何使用 urlfetch 处理 HTTP 异常？

Answer 1

另一种处理错误的方法是使用 handle_exception 创建一个 BaseHandler 并让所有其他处理程序扩展这个处理程序。一个完整的工作示例如下所示:

import webapp2
from google.appengine.api import urlfetch

class BaseHandler(webapp2.RequestHandler):
  def handle_exception(self, exception, debug_mode):
    if isinstance(exception, urlfetch.DownloadError):
      self.response.out.write('Oups...!')
    else:
      # Display a generic 500 error page.
      pass

class MainHandler(BaseHandler):
  def get(self):
    url = "http://www.google.commm/"
    result = urlfetch.fetch(url)
    self.response.write('Hello world!')


app = webapp2.WSGIApplication([
    ('/', MainHandler)
  ], debug=True)

更好的解决方案是在 Debug模式下运行时抛出异常，并在生产环境中以更友好的方式处理它们。取自another example你可以为你的 BaseHandler 做这样的事情，并根据需要扩展它:

class BaseHandler(webapp2.RequestHandler):
  def handle_exception(self, exception, debug_mode):
    if not debug_mode:
      super(BaseHandler, self).handle_exception(exception, debug_mode)
    else:
      if isinstance(exception, urlfetch.DownloadError):
        # Display a download-specific error page
        pass
      else:
        # Display a generic 500 error page.
        pass