apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/component/txtresolver/PropertyResolver.java/PropertyResolver/isHasRepeatKey
class PropertyResolver:  private boolean isHasRepeatKey(String[] newItems, @NotNull Set<String> repeatKeys) {
    Set<String> keys = new HashSet<>();
    int lineCounter = 1;
    for (String item : newItems) {
      if (!isCommentItem(item) && !isBlankItem(item)) {
        String[] kv = parseKeyValueFromItem(item);
        if (kv != null) {
          String key = kv[0].toLowerCase();
          if(!keys.add(key)){
            repeatKeys.add(key);
          }
        } else {
          throw new BadRequestException("line:" + lineCounter + " key value must separate by '='");
        }
      }
      lineCounter++;
    }
    return !repeatKeys.isEmpty();
  }