How to get an Abstract Syntax Tree from IntelliJ IDEA?

I've been trying to build a Java AST using IntelliJ IDEA, but I've had difficulty finding any information on doing so.
Can someone point me in the right direction with regards to this? I want to create the AST primarily for Java, and then potentially for other languages in future.
The idea is to create an AST for a project, then store the AST in a triplestore database.

The built-in PSI Viewer appears to provide something close to what I'm looking for, perhaps there is a way to create something like an AST using PSI objects?

Thanks for any suggestions.