RFR: 8358688: HttpClient: Simplify file streaming in RequestPublishers.FilePublisher [v3]

[Volkan Yazici]

On Sun, 8 Jun 2025 16:38:09 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> Thanks for the clarification.
>
> Hello Volkan,
> 
>> Earlier the regular file check was performed by FIS::new at subscription, hence, NSFE (yes, FIS::new throws NSFE when passed a not-regular file, e.g., a directory) was thrown at subscribe()
> 
> The `NoSuchFileException` is a NIO construct and resides in `java.nio.file` package. So the older `java.io.FileInputStream`'s constructor throwing a `NoSuchFileException` felt odd to me. So I tried this:
> 
> 
> jshell> new FileInputStream(new File("/tmp"))
> 
> 
> that throws a `FileNotFoundException` (which is understandable) and not a `NoSuchFileException`
> 
> 
> |  Exception java.io.FileNotFoundException: /tmp (Is a directory)
> |        at FileInputStream.open0 (Native Method)
> |        at FileInputStream.open (FileInputStream.java:185)
> |        at FileInputStream.<init> (FileInputStream.java:139)
> |        at (#1:1)
> 
> 
> Was it something else in that test failure which was throwing the `NoSuchFileException`?

@jaikiran, your observation is correct. My explanation was worded poorly: I did not want to mean `NSFE` was thrown by `FIS::new`, instead I was stressing that _the exception_ was thrown at subscription-time. All in all, my point still stands: I could not move certain checks from `subscribe()` to `create()`, because of subscription- versus assembly-time difference in exception semantics. I will try to rephrase:

* In the old version,
  * if the passed `Path` was associated with the default file system, and hence, supports `Path::toFile`, `FIS::new` of OIO was used and it throws `FNFE` of OIO.
  * Otherwise, `Files::newIS` of NIO was used throwing `NSFE` of NIO.
  * There was no `NSFE`-to-`FNFE` translation for the latter case.
  * Both `FIS::new`/`Files::newIS` invocations were at subscription-time.
* In the new version, only `Files::newIS` is used, at subscription-time, with (hopefully) sufficient `NSFE`-to-`FNFE` translation to preserve the old exception semantics.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25662#discussion_r2139586673