code: final long getDerivedJmsExpiration() {
          long ts = getTimestamp().longValue();
          long ttl = getTimeToLive().longValue();
          if ((ts <= 0) || (ttl <= 0)) {
              return 0;
          }
          else {
              return (ts + ttl);
          }
      }
docs: Return the derived JmsExpiration for a non-JMS/MQ produced message.
  The value is derived from the Timestamp and TimeToLive values.
  d336582 - now want to return 0 if Timestamp or TimeToLive are 'not set'.
  
  @return long The JmsExpiration value for the JMS message.