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我正在尝试编写一个 Google-Appengine 应用程序，该应用程序在禁用数据存储写入时会很好地失败

目前我的 main() 看起来像这样：

def main():
    make_datastore_readonly()
    try:
        run_wsgi_app(application)
    except CapabilityDisabledError:
        run_wsgi_app(NoWrite)

如果我将 main 设置为：

def main():
    run_wsgi_app(application)

引发异常时，我的应用程序会显示回溯。

如果我将 main 设置为：

def main():
    run_wsgi_app(NoWrite)

它将正确显示我的错误消息（尽管对于每个请求）。

回到我修改过的 main 版本，这个：

def main():
    make_datastore_readonly()
    try:
        run_wsgi_app(application)
    except CapabilityDisabledError:
        run_wsgi_app(NoWrite)

我仍然没有收到我的错误消息，而是得到如下所示的回溯：

Traceback (most recent call last):
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/webapp/_webapp25.py", line 703, in __call__
    handler.post(*groups)
  File "/Users/kevin/Sche/main.py", line 232, in post
    me.put();
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/db/__init__.py", line 1074, in put
    return datastore.Put(self._entity, **kwargs)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/datastore.py", line 579, in Put
    return PutAsync(entities, **kwargs).get_result()
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/datastore.py", line 556, in PutAsync
    return _GetConnection().async_put(config, entities, local_extra_hook)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/datastore/datastore_rpc.py", line 1553, in async_put
    return make_put_call(base_req, pbs, extra_hook)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/datastore/datastore_rpc.py", line 1543, in make_put_call
    self.__put_hook, user_data)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/datastore/datastore_rpc.py", line 1188, in make_rpc_call
    rpc.make_call(method, request, response, get_result_hook, user_data)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/apiproxy_stub_map.py", line 519, in make_call
    self.__service, method, request, response, self.__rpc)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/apiproxy_stub_map.py", line 207, in Call
    function(service, call, request, response)
  File "/Users/kevin/Sche/main.py", line 18, in hook
    raise CapabilityDisabledError('Datastore is in read-only mode')
CapabilityDisabledError: Datastore is in read-only mode

所以，我的问题是，为什么没有捕捉到异常？

编辑：

这个函数来自这个 StackOverflow 答案

def make_datastore_readonly():
  """Throw ReadOnlyError on put and delete operations."""
  def hook(service, call, request, response):
    assert(service == 'datastore_v3')
    if call in ('Put', 'Delete'):
      raise CapabilityDisabledError('Datastore is in read-only mode') //Line 18
  apiproxy_stub_map.apiproxy.GetPreCallHooks().Push('readonly_datastore', hook, 'datastore_v3')
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1 回答 1

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该main功能仅注册此应用程序。因此，异常不会在 main 函数中引发。因此，该try ... catch语句将不起作用。

处理这个异常的方法是定义一个新的 RequestHandler。然后，所有想要具有此功能的请求都应该来自新的 RequestHandler。

例如：

Class MyRequestHandler(RequestHandler):
    def get(self):
        try:
            self.get_handler()
        except CapabilityDisabledError:
            pass

class MyRequest(MyRequestHandler):
    def get_handler(self):
        # ....
        pass
于 2012-08-19T02:11:42.270 回答