Add parameters to Maven Enforcer Rules called from the command line

Following https://stackoverflow.com/a/59389998/927493, one can now call the Maven enforcer plugin from the command line.

This works well, but unfortunately I haven't understood yet whether I can set rule parameters through the command line. An example would be version in the RequireMavenVersion rule.

No you can't. I'm actually not that happy with the current implementation because of these expectations. The first usecase was a simple, parameterless rule. Of course we could predict the next questions.

Let's first explain how "complex" plugin configuration works. Take a look at the following example:

<rules>
  <requireMavenVersion>
    <version/>
  </requireMavenVersion>
</rules>

Here requireMavenVersion is the lowercase classname in the same package as the EnforceMojo(or enforce goal), version is a setter on this class. What you see is nothing more than a Pojo. The only requirement here is that RequireMavenVersion implements the EnforcerRule interface, so Maven can call its execute method see:

 @Parameter
 private EnforcerRule[] rules;

If you want to call a rule from commandline, the plugin simple tries to rename the rule to a full qualified classname make a new instance of it. Next its execute method will be called.

The request for this feature was to enforce rules without touching the project. This should be solved as a Maven Extension, which fits much better to that usecase.

But in conclusion: no you can't.

UPDATE As of Maven Enforcer 3.0.0 there's a Maven Enforcer Extension which gives you an extra way to define enforcer rules.