GAE, App Marketplace, Python and Java

I spent some part of the weekend working on an app which was hosted on Google App Engine (GAE) and hooks into the Google App Marketplace – I learnt a bit about how these systems work together and thought I’d share.

There are some issues with the choice of development languages for an App Marketplace app hosted on GAE – GAE supports Python and Java and App Marketplace currently offers supports for Ruby, Java, C# and PHP. In principle, it is possible for App Marketplace to work with other languages, as it is really just a set of web APIs; however, it could be a bit of work to assemble the right set of libraries to make this work properly.

I did spend a bit of time before looking at using the Python variant of GAE (GAE/P) to develop an app which runs on the Marketplace. However, I found that there are some known problems with Single Sign On for App Marketplace using the Python in AppEngine. For this reason, we chose to use Java in GAE (GAE/J) for the solution.

In my naivety, I had assumed that the GAE/J would be very similar to GAE/P and hence my experience with the latter would make it relatively easy to get a GAE/J app up and running quickly. To my horror, I found that GAE/J is based on Java servlets and is a big world of pain when compared with the ease of GAE/P.

We did make some progress on the concept, but we found that there was a small outfit based in Mountain View doing essentially the same thing – didn’t do the homework properly. We shifted emphasis to produce what is really quite a nice concept – it’s no longer focused on the Marketplace, so we’re going to ditch the Java variant and start again with Python.

Key takeaways for me from this episode:

  • GAE/J is very much more complex than GAE/P – you’d need good reasons to use the former;
  • if you have designs on an App Marketplace hosted app and you haven’t rolled a line of code yet and time is not of the utmost urgency, I’d advise hanging on until there is proper GAE/P support for Marketplace – it shouldn’t be so long

If you’re interested in Marketplace, are hanging around Dublin and free on Nov 30th 2010, you could pop in to the local GTUG for more info on it.

Update: I’m told Google has fixed up this problem in AppEngine 1.4.0, so GAE/P now plays nice with Marketplace. Haven’t tested it as yet, but I’m assuming they know what they’re talking about.


About morphousmusings

Engineer, thinker, tinker, drinker, talker, walker, hiker, biker, liker, lover View all posts by morphousmusings

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