On Mon, 11 Aug 2025 07:47:03 GMT, Volkan Yazici <[email protected]> wrote:
>> Adds a new `ofFileChannel(FileChannel channel, long offset, long length)`
>> method to `java.net.HttpRequest.BodyPublishers` to provide an `HttpClient`
>> publisher to upload a certain region of a file. The new publisher does not
>> modify the state of the passed `FileChannel`, streams the file channel bytes
>> as it publishes (i.e., avoids reading the entire file into the memory), and
>> can be leveraged to implement sliced uploads. As noted in the Javadoc:
>>
>>> The file channel will not be closed upon completion. The caller is
>>> expected to manage the life cycle of the channel, and close it
>>> appropriately when not needed anymore.
>>
>> ### Implementation notes
>>
>> - `FileChannel` is preferred over `{Readable,Seekable}ByteChannel`, since
>> the latter does not provide a positional read without modifying the state of
>> the `FileChannel`, which is necessary to use a single `FileChannel` instance
>> to implement sliced uploads.
>> - `ofFileChannel(FileChannel,long,long)` is preferred over
>> `ofPath(Path,long,long)` to avoid overloading the maximum file descriptor
>> limit of the platform.
>
> Volkan Yazici has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Improve style for declaring multiple consecutive fields of the same type
I'm not sure saying "this method doesn't change the channel position" is
appropriate - indeed it's not the method that would potentially change the
channel position but the body publisher it returns.
On the one hand, not mentioning explicitely that we use
`FileChannel#read(ByteBuffer, long)` doesn't lock us on the implementation; on
the other hand it leaves some uncertainty on how we achieve this and whether
concurrency would effectively work (we could be locking the channel and
resetting its position for instance).
I like the idea of moving that information into an `@apiNote`. Maybe a cross
between your suggested change and what Volkan currently has? Also - though
uploading non-overlapping portions of the file is how you would usually use the
publisher, it is not required that the portions are non-overlapping for
concurrency to work correctly.
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PR Comment: https://git.openjdk.org/jdk/pull/26155#issuecomment-3199960642
