public static String getStringValue(String primaryKey, String secondaryKey) {
        String val = (String) CFG.get(primaryKey);
        if (val == null) {
            val = (String) CFG.get(secondaryKey);
            if (val == null) {
                throw new SofaRpcRuntimeException(LogCodes.getLog(LogCodes.ERROR_NOT_FOUND_KEY, primaryKey + "/" +
                    secondaryKey));
            } else {
                return val;
            }
        } else {
            return val;
        }
    }
Gets string value.

@param primaryKey   the primary key
@param secondaryKey the secondary key
@return the string value
core/api/src/main/java/com/alipay/sofa/rpc/common/RpcConfigs.java