Comment sérialiser db.Modèle d'objets json?

Ok - mon python pas grand, de sorte que toute aide serait appréciée - Vous n'avez pas besoin d'écrire un analyseur - c'est la solution:

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

 import datetime  
import time 
from google.appengine.api import users 
from google.appengine.ext import db 
#this is a mod on the orinal file for some reason it includes its own simplejson files i have ref django!
from django.utils import simplejson  
class GqlEncoder(simplejson.JSONEncoder): 
"""Extends JSONEncoder to add support for GQL results and properties. 
Adds support to simplejson JSONEncoders for GQL results and properties by 
overriding JSONEncoder's default method. 
""" 
# TODO Improve coverage for all of App Engine's Property types. 
def default(self, obj): 
"""Tests the input object, obj, to encode as JSON.""" 
if hasattr(obj, '__json__'): 
return getattr(obj, '__json__')() 
if isinstance(obj, db.GqlQuery): 
return list(obj) 
elif isinstance(obj, db.Model): 
properties = obj.properties().items() 
output = {} 
for field, value in properties: 
output[field] = getattr(obj, field) 
return output 
elif isinstance(obj, datetime.datetime): 
output = {} 
fields = ['day', 'hour', 'microsecond', 'minute', 'month', 'second', 
'year'] 
methods = ['ctime', 'isocalendar', 'isoformat', 'isoweekday', 
'timetuple'] 
for field in fields: 
output[field] = getattr(obj, field) 
for method in methods: 
output[method] = getattr(obj, method)() 
output['epoch'] = time.mktime(obj.timetuple()) 
return output 
elif isinstance(obj, time.struct_time): 
return list(obj) 
elif isinstance(obj, users.User): 
output = {} 
methods = ['nickname', 'email', 'auth_domain'] 
for method in methods: 
output[method] = getattr(obj, method)() 
return output 
return simplejson.JSONEncoder.default(self, obj) 
def encode(input): 
"""Encode an input GQL object as JSON 
Args: 
input: A GQL object or DB property. 
Returns: 
A JSON string based on the input object.  
Raises: 
TypeError: Typically occurs when an input object contains an unsupported 
type. 
""" 
return GqlEncoder().encode(input)   

enregistrer sous json.py

À UTILISER

import cgi
import os
import json 
from google.appengine.ext.webapp import template
from google.appengine.api import users
from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
from google.appengine.ext import db
class Greeting(db.Model):
author = db.UserProperty()
content = db.StringProperty(multiline=True)
date = db.DateTimeProperty(auto_now_add=True)
class MainPage(webapp.RequestHandler):
def get(self):
greetings_query = Greeting.all().order('-date')
greetings = greetings_query.fetch(5)
if users.get_current_user():
url = users.create_logout_url(self.request.uri)
url_linktext = 'Logout'
else:
url = users.create_login_url(self.request.uri)
url_linktext = 'Login'
template_values = {
'greetings': greetings,
'url': url,
'url_linktext': url_linktext,
}
path = os.path.join(os.path.dirname(__file__), 'index.html')
self.response.out.write(template.render(path, template_values))
class Guestbook(webapp.RequestHandler):
def post(self):
greeting = Greeting()
if users.get_current_user():
greeting.author = users.get_current_user()
greeting.content = self.request.get('content')
greeting.put()
self.redirect('/')
#here i return my json feed - simple implementaion for example
class FeedHandler(webapp.RequestHandler):
def get(self):
"""Retrieve a feed"""
user = None
greetings_query = Greeting.all().order('-date')
rs= greetings_query.fetch(5)
#this is the part that calls the encoder - dosnt cause an exception
data = json.encode(rs)
#roll out to browser -might need to check my headers etc
self.response.headers['Content-Type'] = 'application/json; charset=utf-8'  
self.response.out.write(data)
application = webapp.WSGIApplication(
[
('/', MainPage),
('/sign',Guestbook),
('/feed',FeedHandler),
], debug=True
)
def main():
run_wsgi_app(application)
if __name__ == "__main__":
main()

C'est le navigateur réponse:

[{"contenu": "", "date": {"ctime": "Sat Jan 23 02:40:22 2010", "heure": 2, "isoweekday": 6, "mois": 1, "second": 22, "la microseconde": 434000, "isocalendar": [2010, 3, 6], "timetuple": [2010, 1, 23, 2, 40, 22, 5, 23, -1], "année": 2010, "époque": 1264214422.0, "isoformat": "2010-01-23T02:40:22.434000", "jours": 23, "minute": 40}, "auteur": {"pseudo": "[email protected]", "email": "[email protected]", "auth_domain": "gmail.com"}}, {"contenu": "", "date": {"ctime": "Sat Jan 23 01:12:43 2010", "heure": 1, "isoweekday": 6, "mois": 1, "second": 43, "la microseconde": 972000, "isocalendar": [2010, 3, 6], "timetuple": [2010, 1, 23, 1, 12, 43, 5, 23, -1], "année": 2010, "époque": 1264209163.0, "isoformat": "2010-01-23T01:12:43.972000", "jours": 23, "minute": 12}, "auteur": {"pseudo": "[email protected]", "email": "[email protected]", "auth_domain": "gmail.com"}}, {"contenu": "test", "date": {"ctime": "Fri Jan 22 22:32:13 2010", "heure": 22, "isoweekday": 5, "mois": 1, "second": 13, "la microseconde": 659000, "isocalendar": [2010, 3, 5], "timetuple": [2010, 1, 22, 22, 32, 13, 4, 22, -1], "année": 2010, "époque": 1264199533.0, "isoformat": "2010-01-22T22:32:13.659000", "jours": 22, "minute": 32}, "auteur": {"pseudo": "[email protected]", "email": "[email protected]", "auth_domain": "gmail.com"}}, {"contenu": "", "date": {"ctime": "Fri Jan 22 22:29:49 2010", "heure": 22, "isoweekday": 5, "mois": 1, "second": 49, "la microseconde": 358000, "isocalendar": [2010, 3, 5], "timetuple": [2010, 1, 22, 22, 29, 49, 4, 22, -1], "année": 2010, "époque": 1264199389.0, "isoformat": "2010-01-22T22:29:49.358000", "jours": 22, "minute": 29}, "auteur": {"pseudo": "[email protected]", "email": "[email protected]", "auth_domain": "gmail.com"}}, {"contenu": "ah ça marche!\r\n", "date": {"ctime": "Fri Jan 22 22:29:22 2010", "heure": 22, "isoweekday": 5, "mois": 1, "second": 22, "la microseconde": 995000, "isocalendar": [2010, 3, 5], "timetuple": [2010, 1, 22, 22, 29, 22, 4, 22, -1], "l'année": en 2010, "epoch": 1264199362.0, "isoformat": "2010-01-22T22:29:22.995000", "jours": 22, "minute": 29}, "auteur": {"pseudo": "[email protected]", "email": "[email protected]", "auth_domain": "gmail.com"}}]

json ne peut pas être utilisé pour sérialiser quelque chose de plus que les types de base tels que les dicts, des listes, des ints/longs, et les chaînes de caractères (ce qui n'est pas exhaustive). Par exemple, mais ces commandes ne fonctionnent pas:

import json
json.dumps(object())

Si vous souhaitez sérialiser django objets, reportez-vous à la documentation de django sur la sérialisation, qui utilisent leurs propres bibliothèques, mais ils n'en faire le support de json.

De ce que je peux comprendre - et je suis python - avec google app engine le contourner est de sérialiser l'objet de modèle à un dictioanry python objet, puis utilisez simple json pour le dump comme une chaîne json - cela ne fait aucun sens pour moi - peut-être que quelqu'un a le savoir pour serialise à un ditionary (pickel?)
Toute aide sur ce serait de l'AIDE! ne pas impressionné de voir que google app engine n'a pas intégré la solution pour cela.