Logging systems can usually be enabled by package/namespace, and frequently to the class level. I've used AOP to log out the trace of the code (not just the call stack), but can turn it on or off as needed. Authentication acting strange? Enable those logging aspects and browse the log to see where things are behaving strangely, and it may not be in the stack trace of the exception that gets thrown somewhere else. Logging methods and some arguments is hugely helpful; it's like automatic debugging.
Ahh OK. So you mean fine-grained selection and routing of log messages.
I'd never thought of that as AOP, but I suppose it is. And I suppose AOP frameworks provide the machinery to do it, without the logging subsystem having to reinvent those wheels.
Can you expand on how this works in practice. Or link to an explanation? (I assume AOP means "Aspect Oriented Programming").