RFR: 8356645: Javac should utilize new ZIP file system read-only access mode [v9]

[duke]

On Tue, 29 Jul 2025 13:37:44 GMT, David Beaumont <duke at openjdk.org> wrote:

>> This PR seeks to integrate the new ZipFileSystem "accessMode" parameter to open internal ZIP/JAR files as read only, to act as defense in-depth against accidental modification.
>> 
>> Note that this currently also propagates the (currently undocumented) "zipinfo-time" parameter to several other places where ZIP/JAR files are opened, which is likely to improve performance. This was discussed and is expected to be safe (but it's something to be careful about).
>> This will, of course, be thoroughly tested before integration.
>> 
>> It also unifies several places to use a common helper method to obtain the environment map, adds more comments, and changes a small number of affected tests.
>> 
>> I'm also happy to update the original bug description to include the timestamp related changes as necessary.
>
> David Beaumont has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Feedback tweaks.

@david-beaumont 
Your change (at version b5a428d68b68eaeb9f5eaf8ecff5ba54dfb4fad0) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/jdk/pull/25639#issuecomment-3133460367