public String applyFields(final String replaceText, final LogData event) {
    if (replaceText == null) {
      return null;
    }
    InFixToPostFix.CustomTokenizer tokenizer = new InFixToPostFix.CustomTokenizer(replaceText);
    StringBuffer result = new StringBuffer();
    boolean found = false;

    while (tokenizer.hasMoreTokens()) {
      String token = tokenizer.nextToken();
      if (isField(token) || token.toUpperCase(Locale.US).startsWith(PROP_FIELD)) {
        result.append(getValue(token, event).toString());
        found = true;
      } else {
        result.append(token);
      }
    }
    if (found) {
      return result.toString();
    }
    return null;
  }
Apply fields.

@param replaceText replacement text.
@param event       logging event.
@return evaluted expression
olv-core/src/main/java/pl/otros/logview/accept/query/org/apache/log4j/spi/LoggingEventFieldResolver.java