RFR: 8364182: Add jcmd VM.properties command [v5]

[Kieran Farrell]

On Fri, 9 Jan 2026 09:54:08 GMT, Kieran Farrell <kfarrell at openjdk.org> wrote:

>> The goal of this PR is to add a means of exposing security properties at runtime to aid the debugging security related issues/misconfigurations etc. Currently, only initial security properties set at start up can be exposed via the `InitialSecurityProperty` JFR event. 
>> 
>> This patch introduces a new jcmd diagnostic command `VM.properties`, which enables developers to print either the current system properties or security properties of a running Java process via command-line arguments (-system or -security). To avoid clutter within the jcmd command list, the old `VM.system_properties` command is hidden, but not removed so will not break existing usages. The implementation of each is shared to reduce duplication.
>
> Kieran Farrell has updated the pull request incrementally with one additional commit since the last revision:
> 
>   hide command

> Security properties are a somewhat niche set of non-system properties for the security/crypto area. They can't be set on the command line, need to use -Djava.security.properties== to locate a properties file to augment the security properties defined in java.security. So very confusing to developers and maybe it's time to think about whether security properties make sense in 2026.
> 
Should this PR be put on hold until such a disccusion takes place or maybe that would be something a little further down the line?

> As regards the proposal then my initial reaction is to keep it separate, meaning a security_properties rather than properties command.

My initial patch added a seperate command `VM.security_properties` but I merged the two following a suggestion reduce clutter in the the `jcmd <PID> help` output. Happy to revert to a seperate command if we proceed with this and there is a preference to do so.

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PR Comment: https://git.openjdk.org/jdk/pull/29124#issuecomment-3728531839