How to get concrete type of a generic interface

I have an interface

public interface FooBar<T> { }

I have a class that implements it

public class BarFoo implements FooBar<Person> { }

With reflection, I want to take an instance of BarFoo and get that the version of FooBar it implements is Person.

I use .getInterfaces from BarFoo to get back to FooBar, but that doesn't help me find out what T is.