code: public void execute( EnforcerRuleHelper helper )
          throws EnforcerRuleException
      {
  
          // get the project
          MavenProject project = null;
          try
          {
              project = (MavenProject) helper.evaluate( "${project}" );
          }
          catch ( ExpressionEvaluationException eee )
          {
              throw new EnforcerRuleException( "Unable to retrieve the MavenProject: ", eee );
          }
  
          try
          {
              graphBuilder = (DependencyGraphBuilder) helper.getComponent( DependencyGraphBuilder.class );
          }
          catch ( ComponentLookupException e )
          {
              // real cause is probably that one of the Maven3 graph builder could not be initiated and fails with a ClassNotFoundException
              try
              {
                  graphBuilder = (DependencyGraphBuilder) helper.getComponent( DependencyGraphBuilder.class.getName(), "maven2" );
              }
              catch ( ComponentLookupException e1 )
              {
                  throw new EnforcerRuleException( "Unable to lookup DependencyGraphBuilder: ", e );
              }
          }
          
          // get the correct list of dependencies
          Set<Artifact> dependencies = getDependenciesToCheck( project );
  
          // look for banned dependencies
          Set<Artifact> foundExcludes = checkDependencies( dependencies, helper.getLog() );
  
          // if any are found, fail the check but list all of them
          if ( foundExcludes != null && !foundExcludes.isEmpty() )
          {
              String message = getMessage();
              
              StringBuilder buf = new StringBuilder();
              if ( message != null )
              {
                  buf.append( message + "\n" );
              }
              for ( Artifact artifact : foundExcludes )
              {
                  buf.append( getErrorMessage( artifact ) );
              }
              message = buf.toString() + "Use 'mvn dependency:tree' to locate the source of the banned dependencies.";
  
              throw new EnforcerRuleException( message );
          }
  
      }
docs: Execute the rule.
  
  @param helper the helper
  @throws EnforcerRuleException the enforcer rule exception