code: public static RocksDbWrapper openReadOnly(File directory) throws RocksDbException, IOException {
          RocksDbWrapper rocksDbWrapper = new RocksDbWrapper(directory, true);
          rocksDbWrapper.init();
          return rocksDbWrapper;
      }
docs: Open a {@link RocksDB} with default options in read-only mode.
  
  @param directory
  existing {@link RocksDB} data directory
  @return
  @throws RocksDBException
  @throws IOException