private void createShellExecutor(String executorClassName) throws ExecutorException {
    try {
      executor = (SqlExecutor) createInstance(executorClassName);
    } catch (ClassCastException e) {
      String errMsg = String.format("Error trying to cast Object of class %s to SqlExecutor", executorClassName);
      LOG.error(errMsg);
      throw new ExecutorException(errMsg, e);
    } catch (Exception e) {
      LOG.error(e.getMessage());
      throw new ExecutorException(e);
    }
  }
retrieves the list of {@link CommandHandler}s setup in this environment
@return List of {@link CommandHandler}
samza-sql-shell/src/main/java/org/apache/samza/sql/client/cli/CliEnvironment.java