code: private ByteBuffer columnValueAsBytes(ByteBuffer columnName, String columnFamilyName, String columnValue)
      {
          CfDef columnFamilyDef = getCfDef(columnFamilyName);
          AbstractType<?> defaultValidator = getFormatType(columnFamilyDef.default_validation_class);
  
          for (ColumnDef columnDefinition : columnFamilyDef.getColumn_metadata())
          {
              byte[] currentColumnName = columnDefinition.getName();
  
              if (ByteBufferUtil.compare(currentColumnName, columnName) == 0)
              {
                  try
                  {
                      String validationClass = columnDefinition.getValidation_class();
                      return getBytesAccordingToType(columnValue, getFormatType(validationClass));
                  }
                  catch (Exception e)
                  {
                      throw new RuntimeException(e);
                  }
              }
          }
  
          return defaultValidator.fromString(columnValue);
      }
docs: Converts column value into byte[] according to validation class
  @param columnName - column name to which value belongs
  @param columnFamilyName - column family name
  @param columnValue - actual column value
  @return value in byte array representation