Getting started with Cloud Datastore

application: your-app-id
version: 1
runtime: python27
api_version: 1
threadsafe: true
handlers:
- name: jinja2
- url: /favicon\.ico
  static_files: favicon.ico
  upload: favicon\.ico
 
- url: /.*
  script: guestbook.application
 
libraries:
- name: webapp2
  version: latest
- name: jinja2
  version: latest

# this is what configures our Datastore, and allows ndb in guestbook.py to query children
indexes:
# we have kind of Greeting
- kind: Greeting
  # that supports ancestor queries
  ancestor: yes
  properties:
  # on the property 'date'
  - name: date
    # with a direction of descending
    direction: desc

...
          <!-- post to index when submitting -->
          <form role="form" action="" method=post>
              <div class="form-group">
                <textarea class="form-control" name=entry rows="3"></textarea>
              </div>
              <button type="submit" class="btn btn-primary">Submit</button>
          </form>
...
      <ul class="list-group">
        {% for entry in entries %}
        <!-- output the `content` property of each entry -->
        <li class="list-group-item" class=entry>{{ entry.content }}</li>
        {% endfor %}
      </ul>
      
      <!-- post to /clear when clearing entries -->
      <form role=form action="/clear" method=post>
        <button type="submit" class="btn btn-danger">Clear Entries</button>
      </form>
...

import jinja2
import os
import webapp2
 
# Use ndb from the App Engine client libraries to make working with Datastore and
# modeling entities in Python easy
from google.appengine.ext import ndb
 
# define our key here - this is what we use to tie relate our Greeting child entities
# to our parent Guestbook entity
def guestbook_key(guestbook_name='default_guestbook'):
    return ndb.Key('Guestbook', guestbook_name)
 
jinja_environment = jinja2.Environment(
    loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
    extensions=['jinja2.ext.autoescape'],
    autoescape=True)
 
 
# the definition for our Greeting model
class Greeting(ndb.Model):
    content = ndb.StringProperty()
    date = ndb.DateTimeProperty(auto_now_add=True)
 
 
# requests for our app - essentially the same as a route handler in Express
class MainPage(webapp2.RequestHandler):
    # GET requests
    def get(self):
        # create the query to fetch greetings
        # i.e.
        # perform an ancestor query,
        # getting all the children under guestbook_key,
        # and order them descending
        greetings_query = Greeting.query(
            ancestor=guestbook_key()).order(-Greeting.date)
        # get our greetings - the first 10
        greetings = greetings_query.fetch(10)
        # get the template we will populate
        template = jinja_environment.get_template('index.html')
        # send a response using the template above, rendering greetings
        # as the entries value in the template
        self.response.out.write(template.render(entries=greetings))
 
    # POST requests
    def post(self):
        # specify the entity we will be creating
        # This is where we are setting up strong consistency so that this entity
        # has a parent of the specified key
        greeting = Greeting(parent=guestbook_key())
        # set the content of the entity to the `entry` key of the request
        greeting.content = self.request.get('entry')
        # write the entity to Datastore
        greeting.put()
        # redirect the user to the index page
        self.redirect('/')
 
 
# /clear route handler
class Clear(webapp2.RequestHandler):
    # only accepts POST requests. We get a 405 attempting to GET /clear
    def post(self):
        # configure our query
        # fetch only the keys, as that's all we need in order to delete
        # entries. This is more performant than fetching all the data
        # for each entry
        greetings_query = Greeting.query(
            ancestor=guestbook_key()).fetch(keys_only=True)
        # delete entries by passing in the keys for the greetings
        ndb.delete_multi(greetings_query)
        # redirect to index once complete
        self.redirect('/')
        
# map our routes to our route handlers
application = webapp2.WSGIApplication([
    ('/', MainPage),
    ('/clear', Clear),
], debug=True)