RFR: 8350880: (zipfs) Add support for read-only zip file systems [v6]

[Jaikiran Pai]

On Mon, 19 May 2025 12:15:38 GMT, David Beaumont <duke at openjdk.org> wrote:

>> Adding read-only support to ZipFileSystem.
>> 
>> The new `accessMode` environment property allows for readOnly and readWrite values, and ensures that the requested mode is consistent with what's returned.
>> 
>> This involved a little refactoring to ensure that "read only" state was set initially and only unset at the end of initialization if appropriate.
>> 
>> By making 2 methods return values (rather than silently set non-final fields as a side effect) it's now clear in what order fields are initialized and which are final (sadly there are still non-final fields, but only a split of this class into two types can fix that, since determining multi-jar support requires reading the file system).
>
> David Beaumont has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fixed test.

test/jdk/jdk/nio/zipfs/NewFileSystemTests.java line 208:

> 206:         // Multi-release JARs, when opened with a specified version are inherently read-only.
> 207:         Path multiReleaseJar = createMultiReleaseJar();
> 208:         try (FileSystem fs = FileSystems.newFileSystem(multiReleaseJar, Map.of("accessMode", "readWrite"))) {

I wonder if the ZIP filesystem implementation should throw an exception in this case. In the case where the application code has explicitly stated `accessMode=readWrite`, if the underlying file `Path` isn't writable, then we currently throw an `IOException`. I think we should specify and implement the same for the case where `accessMode=readWrite` and the file is a multi-release JAR file.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25178#discussion_r2095637058