private RegionListener getRegionListener() {
    RegionListener rl = null;
    for (RegionListener listener : cache.getRegionListeners()) {
      if (listener instanceof LuceneRegionListener) {
        LuceneRegionListener lrl = (LuceneRegionListener) listener;
        if (lrl.getRegionPath().equals(regionPath) && lrl.getIndexName().equals(indexName)) {
          rl = lrl;
          break;
        }
      }
    }
    return rl;
  }
Register an extension with the region so that xml will be generated for this index.
geode-lucene/src/main/java/org/apache/geode/cache/lucene/internal/LuceneIndexImpl.java