code: private void checkGwtUserVersion() throws MojoExecutionException
      {
          InputStream inputStream = Thread.currentThread().getContextClassLoader()
              .getResourceAsStream( "org/codehaus/mojo/gwt/mojoGwtVersion.properties" );
          Properties properties = new Properties();
          try
          {
              properties.load( inputStream );
  
          }
          catch (IOException e)
          {
              throw new MojoExecutionException( "Failed to load plugin properties", e );
          }
          finally
          {
              IOUtils.closeQuietly( inputStream );
          }
  
          Artifact gwtUser = project.getArtifactMap().get( GWT_USER );
          if (gwtUser != null)
          {
              String mojoGwtVersion = properties.getProperty( "gwt.version" );
              //ComparableVersion with an up2date maven version
              ArtifactVersion mojoGwtArtifactVersion = new DefaultArtifactVersion( mojoGwtVersion );
              ArtifactVersion userGwtArtifactVersion = new DefaultArtifactVersion( gwtUser.getVersion() );
              if ( userGwtArtifactVersion.compareTo( mojoGwtArtifactVersion ) < 0 )
              {
                  getLog().warn( "Your project declares dependency on gwt-user " + gwtUser.getVersion()
                                     + ". This plugin is designed for at least gwt version " + mojoGwtVersion );
              }
          }
      }
docs: Check gwt-user dependency matches plugin version