Distributable application for Google App Engine

I have an idea of web-application.

As an option I'm considering Java+Appengine as technology, but in future I will need possibility to create instances of application without using GAE.

So, I have a questions:

is it possible to migrate application from GAE to some application server (Tomcat for example)?

What I need to take into accoun开发者_如何学运维t from that start for easier migration?

Or In that case it is easier to create application not for GAE?

Thank you!

If you write to the subset of the servlet API that Google provides, then yes.

Use best practice of J2EE development: 1. Separate layers in backend: DAO for data access, Service for bussiness logic. About data model - in any case you'll have to change it when move from AppEngine to Tomcat. Maybe JPA annotations will help you. You can use it with other DB. But if you nead scalability - you have to use NoSQL. 2. Use MVC for frontend with Spring for example

I think you'll have to rewrite your DAO layer and data model. So it is take some time.