Adding a Protocol to Deploy the Site

Out of the box, Maven 3 only supports file:, http: and https: as transport protocols. Maven 2 adds scp: to this list.

If you try to deploy a site with an unsupported protocol, you'll get an error:

[ERROR] 
Unsupported protocol: '...' for site deployment to distributionManagement.site.url=...
Currently supported protocols are: ...
    Protocols may be added through wagon providers.
    For more information, see http://maven.apache.org/plugins/maven-site-plugin/examples/adding-deploy-protocol.html

As explained in the error message, to deploy a site with a non-built-in protocol, you need to add the corresponding wagon provider.

You can add it either as a global extension, or declare it at as a dependency of the site plugin:

<project>
  ...
  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-site-plugin</artifactId>
          <version>3.5.1</version>
          <dependencies>
            <dependency><!-- add support for ssh/scp -->
              <groupId>org.apache.maven.wagon</groupId>
              <artifactId>wagon-ssh</artifactId>
              <version>1.0</version>
            </dependency>
          </dependencies>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
  ...
</project>