It is possible to run, at least, a simple Struts 2 application on GAE with a little work. Namely, you need to tell OGNL to not do security manager permission checks, which will fail since GAE has a security manager and you don't have the ability to add the OGNL-specific permissions. Therefore, somewhere in your initialization code, add this:
OgnlRuntime.setSecurityManager(null);
The easiest place for this is in a Servlet context listener, executing when the context is initialized.
The following features are known not to work:
- Sitemesh plugin, due to Sitemesh not working in GAE