[jetty-users] Creating an HttpClient that does HTTP/2 only over ALPN

[John Gardiner Myers <jgmyers@xxxxxxxxxxxxxx>]

Using Jetty 9.4.12 embedded with Java 11.0.1 and the 
jetty-alpn-java-client processor, I cannot figure out how to construct 
an HttpClient which only uses HTTP/2 when talking to an HTTPS server 
which supports h2 under ALPN, using HTTP/1.1 when talking to an HTTP 
server or an HTTPS server which either does not support ALPN or does not 
support h2.

An HttpClient constructed with a HttpClientTransportOverHTTP2 and a 
SslContextFactory appears to use HTTP/2 in all situations.

Naturally, I'd like to configure any underlying HTTP2Client.

This seems like it would be a common use case, but I cannot find any 
obvious documentation or example code. How does one do this?