code: private void validateGeneratedValueAnnotation(final Class<?> clazz, Field field)
      {
  
          Table table = clazz.getAnnotation(Table.class);
          // Still we need to validate for this after post metadata
          // population.
          if (table != null)
          {
              String schemaName = table.schema();
              if (schemaName != null && schemaName.indexOf('@') > 0)
              {
                  schemaName = schemaName.substring(0, schemaName.indexOf('@'));
                  GeneratedValue generatedValue = field.getAnnotation(GeneratedValue.class);
                  if (generatedValue != null && generatedValue.generator() != null
                          && !generatedValue.generator().isEmpty())
                  {
                      if (!(field.isAnnotationPresent(TableGenerator.class)
                              || field.isAnnotationPresent(SequenceGenerator.class)
                              || clazz.isAnnotationPresent(TableGenerator.class) || clazz
                              .isAnnotationPresent(SequenceGenerator.class)))
                      {
  
                          throw new IllegalArgumentException("Unknown Id.generator: " + generatedValue.generator());
                      }
                      else
                      {
                          checkForGenerator(clazz, field, generatedValue, schemaName);
                      }
                  }
              }
          }
  
      }
docs: validate generated value annotation if given.
  
  @param clazz
  @param field
  @throws RuleValidationException