To use the maven-enforcer-extension, you must register the extension and configuration.
You have 2 ways to use Maven extensions within your builds:
add maven-enforcer-extension-3.0.0.jar in ${maven.home}/lib/ext (no extra dependencies required),
(since Maven 3.3.1) configure your extension in .mvn/extensions.xml.
There is actually a third way: add the extension to the pom.xml, but in that case it makes more sense to use the maven-enforcer-plugin instead.
The .mvn/enforcer-extension.xml in the root of your Maven project is where you define your rules. It’s content is similar to an execution-block of the maven-enforcer-plugin
<extension> <executions> <execution> <id/> <!-- default: default-extension --> <phase/> <!-- default: validate --> <configuration> <!-- see Plugin Configuration --> <rules/> </configuration> </execution> </executions> </extension>