如何响应XMLHttpRequest

Question

I'm using a Javascript to ask our app (which is in Google App Engine) if the file a user wants to upload is already in his list of files (he will overwrite).

I know how to send the request, but how can I create a response from the server, using Python?

This is the request:

var req = new XMLHttpRequest();

  req.open('POST', 'https://safeshareapp.appspot.com/upload', async);

  req.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
  req.setRequestHeader("Content-length", body.length);
  req.setRequestHeader("Connection", "close");

  if (async) {
    req.onreadystatechange = function() {
      if(req.readyState == 4 && req.status == 200) {
        var response = null;
        try {
         response = JSON.parse(req.responseText);
        } catch (e) {
         response = req.responseText;
        }
        callback(response);
      }
    }
  }

  // Make the actual request
  req.send(body);

As you see, we are getting the responseText from the request after everything has gone OK, but my question is how do we fill that responseText field on the server side??

Answer 1

class MyRequestHandler(webapp.RequestHandler):
    def get(self):
        import json
        result = {"filename": xxx} // just an example, result can be any Python object
        json_obj = json.dumps(result)
        self.response.out.write(str(json_obj))