public ValidationError validate(Object value, ExpressionContext expressionContext) {
   Iterator validationRulesIt = validationRules.iterator();
   while (validationRulesIt.hasNext()) {
     ValidationRule validationRule = (ValidationRule) validationRulesIt.next();
     ValidationError result = validationRule.validate(value, expressionContext);
     if (result != null) return result;
   }
   return null;
 }