带有可选Google App Engine支持的标准Java Webapp

Question

I've built plenty of Java webapps that run in standard containers like Tomcat and Jetty, but I've never built one that runs in Google's App Engine before. I'm using Maven, so I had originally thought that I could just do this with build profiles to just optionally include Google's libraries at build time to make an App Engine-compatible WAR.

Unfortunately, it seems to be more complex than that. In reading through the documentation, there seems to be an awful lot of very specific code you have to write in order to use the App Engine. For example, all file system writes need to go through the App Engine data store, so you can't use native java.io.* libraries.

I understand why these things are necessary, and I wouldn't mind having some of this code in my webapp. However, I really don't like the idea that my webapp can only run on the App Engine. Is it possible/feasible to write my code in such a way that I can also run it in a typical container like Tomcat?

Answer 1

It mostly depends on what you app is going to do. You are going to run into troubles as soon as you want to do stuff with the datastore, or caching for example. Perhaps you could wrap things line datastore calls or caching, but certain apis, like search you can forget about. If you just want to run something locally that is no problem you can mock the app engine locally.