Did you use Perf4J in your Java application to collect and analyze performance stats?
What was the typical pattern (using log files, utilities, UI, JMX, etc.)?
Did you use annotations and AOP-based features?
Did you use any JMX integration?
How did you handle production configuration?
Did you include performance stats views/reports as a feature in your application?
Please tell if and why you decided on alternative library/approach.