JSON serialization of Google App Engine models

user_111677 0
Viewed 35749

I've been searching for quite a while with no success. My project isn't using Django, is there a simple way to serialize App Engine models (google.appengine.ext.db.Model) into JSON or do I need to write my own serializer?

Model:

class Photo(db.Model):
    filename = db.StringProperty()
    title = db.StringProperty()
    description = db.StringProperty(multiline=True)
    date_taken = db.DateTimeProperty()
    date_uploaded = db.DateTimeProperty(auto_now_add=True)
    album = db.ReferenceProperty(Album, collection_name='photo')
google-app-engine python json
14 Answers

This is the simplest solution I found. It requires only 3 lines of codes.

Simply add a method to your model to return a dictionary:

class DictModel(db.Model):
    def to_dict(self):
       return dict([(p, unicode(getattr(self, p))) for p in self.properties()])

SimpleJSON now works properly:

class Photo(DictModel):
   filename = db.StringProperty()
   title = db.StringProperty()
   description = db.StringProperty(multiline=True)
   date_taken = db.DateTimeProperty()
   date_uploaded = db.DateTimeProperty(auto_now_add=True)
   album = db.ReferenceProperty(Album, collection_name='photo')

from django.utils import simplejson
from google.appengine.ext import webapp

class PhotoHandler(webapp.RequestHandler):
   def get(self):
      photos = Photo.all()
      self.response.out.write(simplejson.dumps([p.to_dict() for p in photos]))
user_2657730

These APIs (google.appengine.ext.db) are no longer recommended. Apps that use these APIs can only run in the App Engine Python 2 runtime and will need to migrate to other APIs and services before migrating to the App Engine Python 3 runtime. To know more: click here

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