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 224:

> 222:         // Underlying file is read-only.
> 223:         Path readOnlyZip = Utils.createJarFile("read_only.zip", Map.of("file.txt", "Hello World"));
> 224:         readOnlyZip.toFile().setReadOnly();

`java.io.File.setReadOnly()` specifies:

> On some platforms it may be possible to start the
> Java virtual machine with special privileges that allow it to modify
> files that are marked read-only. Whether or not a read-only file or
> directory may be deleted depends upon the underlying system.

So I think we should run the subsequent asserts in this test after first checking if the file was set to read-only. If it isn't then we should skip the test. Something like:


final boolean marked  = readOnlyZip.toFile().setReadOnly();
Assumptions.assumeTrue(marked, "skipping test since " + readOnlyZip + " couldn't be marked read-only");
assertThrows(IOException.class,
                () -> FileSystems.newFileSystem(readOnlyZip, Map.of("accessMode", "readWrite")));

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/25178#discussion_r2095650541