public static String getUserParam(Query query, String paramName) {
        log(utilsLogger, query, "Retrieving user param value: " + paramName);

        if (paramName == null) {
            error(utilsLogger, query, "Parameter name is null");
            return null;
        }

        String paramValue = null;
        paramValue = query.properties().getString(paramName);
        log(utilsLogger, query, "Param value retrieved is: " + paramValue);

        return paramValue;
    }
Get user param value

@param query Query object from the searcher
@param paramName parameter to be retrieved
@return parameter value or null if not found
container-search/src/main/java/com/yahoo/search/query/rewrite/RewriterUtils.java