Enable HTTP/2 for Tomcat 9

It is easier than I thought.

First, ensure you are using APR/native connector. You can download tomcat native from here. Put the tcnative-1.dll in the tomcat lib directory.

Second, change protocol to org.apache.coyote.http11.Http11AprProtocol and add the UpgradeProtocol tag.

$CATALINA_HOME\conf\server.xml

<Connector port="8443"
  protocol="org.apache.coyote.http11.Http11AprProtocol"
  maxThreads="150" SSLEnabled="true">
    <UpgradeProtocol overheadDataThreshold="0" compression="on" className="org.apache.coyote.http2.Http2Protocol" />
    <SSLHostConfig honorCipherOrder="false">
        <Certificate certificateKeyFile="conf/ca.key"
          certificateFile="conf/ca.crt"
          type="RSA" />
    </SSLHostConfig>
</Connector>

Restart tomcat and we are done.

Check if HTTP/2 is enabled
https://tools.keycdn.com/http2-test