How to configure a proxy server for both HTTP and HTTPS in Maven’s settings.xml?

Maven proxy from settings.xml is used for both http and https, so you just need to define one proxy server and it will be used for both, you just need to leave only one proxy tag, like this:

<proxies>
    <proxy>
        <id>myhttpproxy</id>
        <active>true</active>
        <protocol>http</protocol>
        <host>192.168.1.2</host>
        <port>3128</port>
        <nonProxyHosts>localhost</nonProxyHosts>
    </proxy>
</proxies>

The protocol above is the protocol of the proxy server, not the proxied request.