Question

I’m getting started with Google App Engine. I want to make AJAX chat like Twitter.

class ChatMessage(db.Model):
  message = db.StringProperty()
  created = db.DateTimeProperty(auto_now=True)

Server JSON encodes the response,

class RPCHandler(webapp.RequestHandler):
  def get(self):
    chat_list = {'message':'Hello!'}
    self.response.out.write(simplejson.dumps(chat_list))

Result: Hello!

This is OK. But replace RPCHandler

class RPCHandler(webapp.RequestHandler):
  def get(self):
    newchat = ChatMessage(message="Hi!")
    newchat.put()
    que = db.Query(ChatMessage).order('-created')
    chat_list = que.fetch(limit=1)

    self.response.out.write(simplejson.dumps(chat_list))

Result: Error. The server is not accessible (get)

How can I JSON encode Entities?

Answer 1

In App Engine Python you can use this script to encode db.Models to JSON. You may have to customize some parts, like the DateTime formatting.

http://code.google.com/p/google-app-engine-samples/source/browse/trunk/geochat/json.py?r=55