AbstractHandshakeHandler does not support HTTP/2 CONNECT (RFC 8441)

[jazdw]

If the web server advertises that it supports RFC 8441 via the HTTP/2 SETTINGS_ENABLE_CONNECT_PROTOCOL parameter then some web browsers (Chrome, Firefox) will follow RFC 8441 to open a WebSocket over a HTTP/2 stream using the CONNECT HTTP method.

The org.springframework.web.socket.server.support.AbstractHandshakeHandler#doHandshake method however only supports the GET method and will respond with 405 Method Not Allowed. and log an error message: Handshake failed due to unexpected HTTP method: CONNECT

The work around is to disable RFC 8441 in your web server, e.g. with Jetty you can set org.eclipse.jetty.http2.server.AbstractHTTP2ServerConnectionFactory#setConnectProtocolEnabled to false (the default is that it is enabled in Jetty 12 EE10).

This problem was observed in Spring 6.2.0.

spring-framework/spring-websocket/src/main/java/org/springframework/web/socket/server/support/AbstractHandshakeHandler.java

Lines 172 to 179 in f8fd6da

	if (HttpMethod.GET != request.getMethod()) {
	response.setStatusCode(HttpStatus.METHOD_NOT_ALLOWED);
	response.getHeaders().setAllow(Collections.singleton(HttpMethod.GET));
	if (logger.isErrorEnabled()) {
	logger.error("Handshake failed due to unexpected HTTP method: " + request.getMethod());
	}
	return false;
	}