RFR: 8283335 : Add exists and readAttributesIfExists methods to FileSystemProvider

[Brian Burkhalter]

On Thu, 23 Jun 2022 07:18:07 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> src/java.base/unix/classes/sun/nio/fs/UnixFileAttributes.java line 80:
>> 
>>> 78:     static UnixFileAttributes getIfExists(UnixPath path) throws UnixException {
>>> 79:         UnixFileAttributes attrs = new UnixFileAttributes();
>>> 80:         int errno = UnixNativeDispatcher.stat2(path, attrs);
>> 
>> I think that this is the only use of `stat2()`. It could be deleted if this method were replaced with this:
>> 
>> 
>>     static UnixFileAttributes getIfExists(UnixPath path) throws UnixException {
>>         UnixFileAttributes attrs = new UnixFileAttributes();
>>         try {
>>             UnixNativeDispatcher.stat(path, attrs);
>>             return attrs;
>>         } catch (UnixException e) {
>>             if (e.errno() == UnixConstants.ENOENT) {
>>                 return null;
>>             }
>>             throw e;
>>         }
>>     }
>
>> I think that this is the only use of `stat2()`. It could be deleted if this method were replaced with this:
> 
> The purpose of these additions to the SPI is to improve the performance of user facing methods that don't throw an exception when the file doesn't exist. It needs a stat/equivalent that doesn't throw so this is the reason for stat2. The equivalent on Windows will need to added too.

Understood.

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PR: https://git.openjdk.org/jdk/pull/9249