code: public static RocksDbWrapper openReadOnly(String dirPath, DBOptions dbOptions,
              ReadOptions readOptions) throws RocksDbException, IOException {
          RocksDbWrapper rocksDbWrapper = new RocksDbWrapper(dirPath, true);
          rocksDbWrapper.setDbOptions(dbOptions).setReadOptions(readOptions);
          rocksDbWrapper.init();
          return rocksDbWrapper;
      }
docs: Open a {@link RocksDB} with specified options in read-only mode.
  
  @param dirPath
  existing {@link RocksDB} data directory
  @param dbOptions
  @param readOptions
  @return
  @throws RocksDBException
  @throws IOException