Notes on converting an GWT + AppEngine web app using Objectify to a plain GWT + MongoDB web app

There has been a lot of noise in blog-space criticizing Google for the re-pricing of AppEngine services. I don't really agree with a lot of the complaints because it seems fair for Google to charge enough to make AppEngine a long term viable business.

That said, I have never done any customer work targeting the AppEngine platform because no one has requested it. (Although I have enthusiastically used AppEngine for some of my own projects and I have written several AppEngine and Wave specific articles.) I still host KnowledgeBooks.com on AppEngine.

I wrote a GWT + AppEngine app for my own use about a year ago, and since I always have at least one EC2 instance running for my own experiments and development work I decided to move my app. It turns out that converting my app is fairly easy using these steps:

• Copy my IntelliJ project, renaming it and removing AppEngine facets and libraires.
• Add the MongoDB Java required JARs
• I had all of my Objectify datastore operations in a single utility class on the server side - I converted this to use MongoDB

Sure, a complex application would take a while, but my app only has 6 model classes (all POJOs) so the whole process took less than 90 minutes.