How to use of the Maven Enforcer plugin?

Question

I'd like to use the Maven Enforcer plugin to check to see if I have duplicate classes on my path.

I've tried the example from here.

But when I run it like this:

mvn enforcer:enforce

I get this error:

Failed to execute goal org.apache.maven.plugins:maven-enforcer-plugin:1.0.1:enforce (default-cli) on project datapopulator: The parameters 'rules' for goal org.apache.maven.plugins:maven-enforcer-plugin:1.0.1:enforce are missing or invalid

Is there a way to use this correctly?

EDIT #1

If changing my config to this:

        <plugin>             <groupId>org.apache.maven.plugins</groupId>             <artifactId>maven-enforcer-plugin</artifactId>             <version>1.0.1</version>             <executions>                 <execution>                     <id>enforce-versions</id>                     <goals>                         <goal>enforce</goal>                     </goals>                     <configuration>                         <rules>                             <AlwaysPass />                         </rules>                         <fail>true</fail>                     </configuration>                 </execution>             </executions>         </plugin> 

Produces the same error.

Answer 1

The reason why your first version did not work is because there is a difference between a plug-in configuration inside the execution tag and a plug-in configuration outside the execution tag. The execution is only used when your plug-in is triggered by a special phase of the complete Maven build.

The Maven guide to configuration explains it better:

Configurations inside the tag differ from those that are outside in that they cannot be used from a direct command line invocation. Instead they are only applied when the lifecycle phase they are bound to are invoked. Alternatively, if you move a configuration section outside of the executions section, it will apply globally to all invocations of the plugin.

Answer 2

Try this, moving the configuration outside executions, so it isn't bound to the life cycle phase.

<plugin>     <groupId>org.apache.maven.plugins</groupId>     <artifactId>maven-enforcer-plugin</artifactId>     <version>1.0.1</version>     <executions>         <execution>             <id>enforce-versions</id>             <goals>                 <goal>enforce</goal>             </goals>         </execution>     </executions>     <configuration>         <rules>             <AlwaysPass />         </rules>         <fail>true</fail>     </configuration> </plugin> 

Now when you do mvn enforcer:enforce, it picks the rules from your pom.xml.