code: private static File getPluginDir() {
          String dataDirPath = System.getProperty("jboss.server.data.dir"); //$NON-NLS-1$
          File dataDir = new File(dataDirPath);
          if (!dataDir.isDirectory()) {
              throw new RuntimeException("Failed to find WildFly data directory at: " + dataDirPath); //$NON-NLS-1$
          }
          File pluginsDir = new File(dataDir, "apiman/plugins"); //$NON-NLS-1$
          return pluginsDir;
      }
docs: Creates the directory to use for the plugin registry.  The location of
  the plugin registry is in the Wildfly data directory.