any event when system properties are changed?

[Jack Zhou]

I have set a system property same named, say , key via System.setProperty() call. But some how it is reset by some code out of my control. I wonder is there a way I can detect the change of this property. For example, is there any event I can catch when certain property values get reset.
Thanks,

[Peter Chase]

No, I don't think there is any way to be notified of changes to system properties.

It is not clear from your description whether you really need to use a system property. What do you need to achieve?

[Jack Zhou]

I was trying find out why some of the system property I set get reseted.
Thanks,

[Jim Hicks]

System properties apply to the JVM. When the JVM executes multiple apps may be executing in it. Any app in the JVM can change a system property that is not restricted. In general, I don't recommend setting system properties unless it is for a property value that is for all the apps in the JVM.

However, to answer the question, access to the System object is controller by the SecurityManager. When you start the JVM, a security manager can be loaded. This security manager will be notified of any attempt to change a system property. However, if you are on a j2ee web server, you may not be able to load your own security manager as most J2ee environments supply a security manager that you cant override. These seucrity managers usually have a way to restrict system property changes. You can restrict the changes and see who get a the SecurityException.