RFR: JDK-8285497: Add system property for Java SE specification maintenance version [v5]

[Joe Darcy]

On Fri, 29 Apr 2022 17:11:55 GMT, Mark Reinhold <mr at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/System.java line 743:
>> 
>>> 741:      *         have the value {@code "1"}; after a second maintenance
>>> 742:      *         release, this property will have the value {@code "2"},
>>> 743:      *         and so on.
>> 
>> There should be no requirement that values be allocated sequentially.  In other words, if JCP MR <x> does not require an RI, then it should not be surprising if there is no JDK build with maintenance version <x>.  As an example, JSR 337 MR 1 and MR 2 both used the same RI.  If this system property had existed during development of MR 1, it would return "1".  Since no RI was submitted for MR 2, a build returning "2" should never exist.  MR 3 did update the RI, so it would return "3".
>
> @irisclark does raise an interesting point: If, say, MR 2 doesn’t require a change to the RI then the MR 1 RI is also the MR 2 RI, but its `java.specification.maintenance.version` property will report that it’s the MR 1 RI.
> 
> One way to fix this would be to require an RI update with every MR just to update this property, even if no other code in the RI changes — but we prefer to avoid doing RI builds unnecessarily.
> 
> Another way to fix it would be to finesse the specification of this property, perhaps:
> 
> 
>      * <tr><th scope="row">{@systemProperty java.specification.maintenance.version}</th>
>      *     <td>Java Runtime Environment specification maintenance version, which may
>      *         be interpreted as a non-zero integer. If defined, the value of this
>      *         property is the identifying number of the most recent <a
>      *         href="https://jcp.org/en/procedures/jcp2#3.6.4">specification
>      *         maintenance release</a> that required a change to the runtime</a>
>      *         <em>(optional)</em>.
>      *         </td></tr>

In the latest push, to address the concerns raised updated the proposed wording to, in plain text:

Java Runtime Environment specification maintenance version, not defined before the specification implemented by this runtime has undergone a maintenance release (optional). When defined, the value of this property may be interpreted as a positive integer. The value indicates the latest maintenance release the runtime is known to support. A later release may be supported by the environment. To indicate the first maintenance release this property will have the value "1"; to indicate the second maintenance release, this property will have the value "2", and so on.

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PR: https://git.openjdk.java.net/jdk/pull/8437