How to detect if a Java System property has changed?

Question

I would like to know when a System property is changed. I have an application, in an application server, that somehow is changing a system property (System.setProperty() I think). I was taking a look and I have found different approaches:

1. JPDA?
2. Observer & Observable?
3. Property change listener?
4. JMX?

Any suggestions? Thanks in advance.

Answer 1

You can replace the system Properties with your own custom subclass.

MyProperties newProps = new MyProperties(System.getProperties());
System.setProperties(newProps);

Then, just write a subclass of Properties which hooks the relevant methods.

Answer 2

If you primarily want to find the issue, I would look at using the SecurityManager for this. It has a couple methods available checkPropertiesAccess() and checkPropertyAccess() which look like they will help you to find the issue, but not necessarily be able to 'notify you when a system property has changed.'