code: private static File getPluginDir() {
          String dataDirPath = System.getProperty("catalina.home"); //$NON-NLS-1$
          File dataDir = new File(dataDirPath, "data"); //$NON-NLS-1$
          if (!dataDir.getParentFile().isDirectory()) {
              throw new RuntimeException("Failed to find Tomcat home at: " + dataDirPath); //$NON-NLS-1$
          }
          if (!dataDir.exists()) {
              dataDir.mkdir();
          }
          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 tomcat data directory.