Question

In my GAE application, I have several request handlers that return JSON-formated response. When one of these is called, if an error occurs (exception, or programming error), the output is not JSON: it is the stack trace.

What I need is:

Output without error:
{
    "foo" : 1
    "bar" : 2
    "status" : "OK"
}

Output when an error occurs:
{
    "status" : "ERR"
    "errorMessage" : "An error occurred!"
}

My question is: What is the best practice to make sure that, in any case, the output will be a JSON-formated response? Of course, a common solution for every request handlers would be great.

Any help would be appreciated.

Answer 1

Sure – use the ereporter class (described here: https://stackoverflow.com/a/4296664/336505), but create a custom BaseHandler that formats your uncaught exceptions as JSON output:

class BaseHandler(webapp.RequestHandler):
    def handle_exception(self, exception, debug_mode):
      self.response.headers['Content-Type'] = 'application/json'
      self.response.out.write(etc, etc) # format the exception