Should some JDK system properties be read only ?

[Alan Bateman]

On 04/12/2014 15:42, Seán Coffey wrote:
> Apologies if this has been raised in past. I've run into issues in the 
> past where bad user code (app server) has set the java.home system 
> property to a value other than the default. This has consequences for 
> apps/code that depend heavily on java.home returning the correct 
> location. The case I saw was a JDK 7 runtime attempting to load JDK 6 
> config files (since java.home was pointing to JDK 6)
>
> It leads me to question on whether we should change this behaviour. 
> There are a whole bunch of properties that make no sense to change. 
> Those like : java.version, java.vendor, java.home, 
> java.vm.specification.version, java.vm.specification.vendor, 
> java.vm.specification.name, java.vm.version, java.vm.vendor, 
> java.vm.name, java.specification.version, java.specification.vendor, 
> java.specification.name.
>
> Should we consider making them read only for JDK 9 and later ?
>
As it happens I ran into a test a few days ago that was changing 
java.home mid-flight. Lots of things can potentially go wrong when 
changing an important property like (user.dir is another one).

It would have been nice if there had been a concept of final/set-once 
system property a long time ago, hard to know if it's worth it now but 
no harm trying if you can come up with something that wouldn't have a 
significant compatibility impact. I could imagine System.setProperties 
requiring work to merge in the new properties so that the important 
properties are replaced.

-Alan.