private String formatExp(final String expPrefix, String expSuffix, String exp) {
        String ret = exp;
        if (!Strings.isNullOrEmpty(expPrefix)) {
            ret = String.format("(%s.%s)", StringUtils.substringBefore(exp, "."), expPrefix);
            final String after = StringUtils.substringAfter(exp, ".");
            if (!Strings.isNullOrEmpty(after)) {
                ret = String.format("(%s.%s)", ret, after);
            }
        }
        if (!Strings.isNullOrEmpty(expSuffix)) {
            ret = String.format("(%s).%s", ret, expSuffix);
        }
        return ret;
    }
MetricConvert converts {@link SampleFamily} collection to meter-system metrics, then store them to backend storage.
oap-server/analyzer/meter-analyzer/src/main/java/org/apache/skywalking/oap/meter/analyzer/MetricConvert.java