This gist implements an Image Uploader Service in python using Google App Engine. There are four components. image.py implements the Image Model to persist Image Resource. image_service.py implements image service client which provides basis functionality of retrieving, saving, updating and deleting an image resource. image_rest_handler.py imple…

image.py

import datetime
from google.appengine.ext import db

class Image(db.Model):
    """Model to represent Image
    """
    name = db.StringProperty(required = True)
    data = db.TextProperty(required = True)
    created_at = db.DateTimeProperty(auto_now_add = True)
    updated_at = db.DateTimeProperty(auto_now = False)

    def to_dict(self):
        return {
            'name': self.name,
            'src': self.data,
            'id': str(self.key()),
            }

image_rest_handler.py

import json
from google.appengine.ext import db
from datetime import datetime
from base import BaseHandler
import logging
from models.image import Image
import image_service  #image service layer

log = logging.getLogger(__name__)

class ImageRestHandler(BaseHandler):
    def get(self, id = None):
        log.info("Image Get request received for %s" % id)
        if id:
            try:
                img = image_service.get(id)
                if img:
                    resp = img.to_dict()
                else:
                    self.abort(404)
            except db.BadKeyError:
                self.abort(404)
        else:
            start = int(self.request.get('start', "0"))
            count = int(self.request.get('count', 16))
            images = image_service.multi_get(limit = count, offset = start)
            resp = []
            for x in images: resp.append(x.to_dict())
        return self.render_json(resp)


    def post(self, id = None):
        """Save a new image
        """
        log.info('Image Post request received: %s' % (self.request.body))

        resp = {}

        try:
            input_img = json.loads(self.request.body)
            if input_img.get('name', None) is None or \
                    input_img.get('src', None) is None:
                    #Bad Request missing args
                    self.abort(400)
        except json.ValueError:
            self.abort(400) #bad request

        img = image_service.create(name = input_img.get('name'), data = input_img.get('src'))
        resp = img.to_dict()
        return self.render_json(resp)

    def put(self, id = None):
        """Update a Tracker Information
        """
        log.info("Image update request received for %s" % id)
        if id is None:
            self.abort(400) #bad request
        try:
            input_img = json.loads(self.request.body)
        except json.ValueError:
            self.abort(400) #bad request

        resp = {}
        img = image_service.update(id, **input_img)
        if img is None:
            self.abort(400)
        else:
            resp = img.to_dict()

        return self.render_json(resp)

    def delete(self, id = None):
        """Delete an Image resource
        """
        log.info("Image Delete request received for %s" % id)
        if id is None:
            self.abort(400)

        img = image_service.delete(id)
        if img:
            return self.render_json(img.to_dict())
        else:
            self.abort(400)

image_service.py

"""This file implement image service module. This service is responsible for providing the
    service abstraction to higher level module like Image REST Controller
"""

from models.image import Image

DEFAULT_PAGE_SIZE = 10

def get(id):
    return Image.get(id)

def multi_get(offset = 0, limit = DEFAULT_PAGE_SIZE):
    q = Image.all()
    return q.order('-created_at').run(limit = limit, offset = offset)

def create(**kwargs):
    img = Image(**kwargs)
    img.put()
    return img

def update(id, **kwargs):
    img = get(id)
    if not img:
        return None

    if kwargs.get('name', None):
        img.name = kwargs.get('name')
    if kwargs.get('src', None):
        img.data = kwargs.get('src')

    img.put()
    return img

def delete(id):
    img = Image.get(id)
    if img:
        img.delete()
        return img
    else:
        return None

test_image_service.py

#!/usr/bin/env python
"""Quick script to test the image REST service
"""
import requests
import json


URL = 'http://localhost:8080/images'

IMAGE_CREATE_DATA = { 'name': 'Test Image', 'src': 'data 1'}
IMAGE_UPDATE_DATE = {'name': 'Test Image2', 'src': 'data 2'}

def test_post():
    r = requests.post(URL, data = json.dumps(IMAGE_CREATE_DATA))
    assert r.status_code == 200
    resp = json.loads(r.content)
    print "Image POST OK"
    assert resp.get('name') == IMAGE_CREATE_DATA.get('name') and \
            resp.get('src') == IMAGE_CREATE_DATA.get('src')
    return resp

def test_get(image_data):
    r = requests.get(URL + "/%s" % (image_data.get('id')))
    assert r.status_code == 200
    resp = json.loads(r.content)
    assert resp.get('id') == image_data.get('id')
    print "Image GET OK"
    return resp

def test_put(image_data):
    r = requests.put(URL + "/%s" % (image_data.get('id')), data = json.dumps(IMAGE_UPDATE_DATE))
    assert r.status_code == 200
    resp = json.loads(r.content)
    assert resp.get('id') == image_data.get('id') and \
            resp.get('name') == IMAGE_UPDATE_DATE.get('name') and \
            resp.get('src') == IMAGE_UPDATE_DATE.get('src')
    print "Image PUT OK"
    return image_data

def test_delete(image_data):
    r = requests.delete(URL + "/%s" % (image_data.get('id')))
    assert r.status_code == 200
    resp = json.loads(r.content)
    assert resp.get('id') == image_data.get('id')
    print "Image DELETE OK"

if __name__ == '__main__':
    import sys

    if len(sys.argv) == 2:
        URL = sys.argv[1]

    image = test_post()
    image = test_get(image)
    image = test_put(image)
    test_delete(image)