[SignalR] Don't throw for message headers in Java client

[BrennanConroy]

Fixes #62713

[Copilot]

Pull Request Overview

This PR updates the Java SignalR client to gracefully ignore message headers instead of throwing, and adds tests to verify header parsing across various message types.

• The GsonHubProtocol is modified to skip over the "headers" JSON property rather than throwing an exception.
• New unit tests in GsonHubProtocolTest ensure invocation, completion, and streaming messages with headers (including empty and reordered headers) are parsed without error.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/SignalR/clients/java/signalr/core/src/main/java/com/microsoft/signalr/GsonHubProtocol.java	Replace exception on "headers" field with code that skips its contents
src/SignalR/clients/java/signalr/test/src/main/java/com/microsoft/signalr/GsonHubProtocolTest.java	Add tests covering parsing of messages with headers in different scenarios

[Copilot]

You can simplify skipping the entire headers object by using reader.skipValue() instead of manually iterating through each property—this reduces boilerplate and potential parsing errors.

Suggested change

	// Parse headers as Map<String, String> but don't store for now as it's unused
	reader.beginObject();
	while (reader.hasNext()) {
	reader.nextName(); // Read the key
	reader.nextString(); // Read the value
	}
	reader.endObject();
	// Skip the entire headers object as it's unused
	reader.skipValue();

[captainsafia]

I'm not a Java expert but I looked up this API and it seems like JsonReader.skipValue is a better way to skip processing the entire "headers" object. Is there a reason we aren't using it here, especially if the value isn't stored?

[DeagleGross]

ye, seems a nice API to use here. also as Brennan explained in one of the issue comments headers are parsed in MessagePack - but they are used later:

aspnetcore/src/SignalR/clients/java/signalr/messagepack/src/main/java/com/microsoft/signalr/messagepack/MessagePackHubProtocol.java

Line 194 in 36e93fa

Map<String, String> headers = readHeaders(unpacker);

aspnetcore/src/SignalR/clients/java/signalr/messagepack/src/main/java/com/microsoft/signalr/messagepack/MessagePackHubProtocol.java

Line 224 in 36e93fa

return new InvocationMessage(headers, invocationId, target, arguments, streams);

why do we completely ignore them here?

[BrennanConroy]

why do we completely ignore them here?

They aren't really used. We set them on the messages but don't actually use them.

Is there a reason we aren't using it here, especially if the value isn't stored?

It doesn't really matter what we do here, but I do like the current code since it technically validates the json is {string:string} whereas skip would just validate that some type of object exists.

[DeagleGross]

makes sense, approved.

[BrennanConroy]

/backport to release/9.0

[github-actions]

Started backporting to release/9.0: https://github.com/dotnet/aspnetcore/actions/runs/16352820503

[BrennanConroy]

/backport to release/8.0

[github-actions]

Started backporting to release/8.0: https://github.com/dotnet/aspnetcore/actions/runs/16352823734