RFR: 8356645: Javac should utilize new ZIP file system read-only access mode [v8]

[Jan Lahoda]

On Mon, 28 Jul 2025 16:43:15 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:
> 
>   Update copyright year.

Overall looks good, two small suggestions for cleanup inline.

test/langtools/tools/javac/jvm/ClassRefDupInConstantPoolTest.java line 2:

> 1: /*
> 2:  * Copyright (c) 2014, 2025, Oracle and/or its affiliates. All rights reserved.

There's no change in this file, this year change can presumably be dropped.

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PR Review: https://git.openjdk.org/jdk/pull/25639#pullrequestreview-3064139247
PR Review Comment: https://git.openjdk.org/jdk/pull/25639#discussion_r2237521343