RFR: 8355572: Support HTTP Range requests in Simple Web Server [v6]

[Michael McMahon]

On Fri, 31 Oct 2025 10:12:27 GMT, Peyang <duke at openjdk.org> wrote:

>> Hi all,
>> 
>> [JEP 408](https://openjdk.org/jeps/408) introduced the Simple Web Server in Java 18, providing a minimal webserver for serving static files over HTTP.
>> 
>> [RFC 9110](https://www.rfc-editor.org/rfc/rfc9110.html#name-range-requests) defines "Range Requests" as an optional feature that allows clients to request a subset of a resource's content. Supporting Range requests in the context of JDK's Simple Web Server means enabling the server to serve only the requested portion of a static file.
>> 
>> This change contains:
>> 
>> 1. Enhances `sun.net.httpserver.simpleserver.FileServerHandler` in the `jdk.httpserver` module to support `Range` and `If-Range` headers.
>> 2. Calculates an `ETag` for each resource based on its last-modified date and file size and sends it to the client on demand for use with the `If-Range` header.
>> 3. Returns the `Accept-Ranges` header for all file retrievals, and `Content-Range` when a client requests a specific range.
>> 4. Adds a new constant `HTTP_RANGE_NOT_SATISFIABLE` to the `Codes` class to indicate invalid ranges.
>> 5. Returns `206 Partial Content` for valid ranges and `416 Range Not Satisfiable` for invalid ranges.
>> 6. Includes corresponding tests to verify correct behavior.
>> 
>> This enhancement was motivated by recent discussions on the net-dev mailing list, which requested support for Range requests along with example use cases: https://mail.openjdk.org/pipermail/net-dev/2025-April/026364.html
>> It was also discussed briefly on the net-dev mailing list: https://mail.openjdk.org/pipermail/net-dev/2025-October/028586.html
>
> Peyang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add documentation for HTTP range requests support in SimpleFileServer

This looks like a useful enhancement. 

One comment - we probably should send the "Accept-Ranges" header in response to a HEAD request also.

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PR Comment: https://git.openjdk.org/jdk/pull/28021#issuecomment-3472517222