RFR: 8332303: Better JMX interoperability with older JDKs, after removing Subject Delegation [v5]

[Chris Plummer]

On Fri, 24 May 2024 17:15:31 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

>> Running JConsole from a previous JDK, and attaching to jdk-23 (after [JDK-8326666](https://bugs.openjdk.org/browse/JDK-8326666): Remove the Java Management Extension (JMX) Subject Delegation feature), the MBean tab is blank.
>> 
>> In javax/management/remote/rmi/RMIConnectionImpl.java:
>> addNotificationListener rejects a non-null delegationSubjects array, but older JDKs will send such an array. It could accept the array, and only reject/throw if it contains a non-null Subject (i.e. if an attempt to use subject delegation is really happening).
>> 
>> Manually testing JConsole, the MBean tab is fully populated and usable.
>
> Kevin Walls has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove should... from delegationSubjects param

src/java.management.rmi/share/classes/javax/management/remote/rmi/RMIConnection.java line 978:

> 976:      * @throws IOException if a general communication exception occurred.
> 977:      * @throws UnsupportedOperationException if {@code delegationSubjects}
> 978:      * is non-null and contains any non-null values.

Minor consistency issue. For the `delegationSubjects` comment above, you refer to "non-null entries". Here you refer to "non-null values". I don't have a preference on which you use, but they should be the same in both cases.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19253#discussion_r1613843199