聊聊artemis JMSBridge的QualityOfServiceMode

public enum QualityOfServiceMode {
   AT_MOST_ONCE(0), DUPLICATES_OK(1), ONCE_AND_ONLY_ONCE(2);
​
   private final int value;
​
   QualityOfServiceMode(final int value) {
      this.value = value;
   }
​
   public int intValue() {
      return value;
   }
​
   public static QualityOfServiceMode valueOf(final int value) {
      if (value == AT_MOST_ONCE.value) {
         return AT_MOST_ONCE;
      }
      if (value == DUPLICATES_OK.value) {
         return DUPLICATES_OK;
      }
      if (value == ONCE_AND_ONLY_ONCE.value) {
         return ONCE_AND_ONLY_ONCE;
      }
      throw new IllegalArgumentException("invalid QualityOfServiceMode value: " + value);
   }
​
}

public final class JMSBridgeImpl implements JMSBridge {
​
   //......
​
   private void sendBatchNonTransacted() {
      try {
         if (qualityOfServiceMode == QualityOfServiceMode.ONCE_AND_ONLY_ONCE || (qualityOfServiceMode == QualityOfServiceMode.AT_MOST_ONCE && maxBatchSize > 1)) {
            // We client ack before sending
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            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Client acking source session");
            }
​
            messages.getLast().acknowledge();
​
            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Client acked source session");
            }
         }
​
         boolean exHappened;
​
         do {
            exHappened = false;
            try {
               sendMessages();
            } catch (TransactionRolledbackException e) {
               ActiveMQJMSBridgeLogger.LOGGER.transactionRolledBack(e);
               exHappened = true;
            }
         }
         while (exHappened);
​
         if (maxBatchSize > 1) {
            // The sending session is transacted - we need to commit it
​
            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Committing target session");
            }
​
            targetSession.commit();
​
            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Committed target session");
            }
         }
​
         if (qualityOfServiceMode == QualityOfServiceMode.DUPLICATES_OK) {
            // We client ack after sending
​
            // Note we could actually use Session.DUPS_OK_ACKNOWLEDGE here
            // For a slightly less strong delivery guarantee
​
            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Client acking source session");
            }
​
            messages.getLast().acknowledge();
​
            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Client acked source session");
            }
         }
      } catch (Exception e) {
         if (!stopping) {
            ActiveMQJMSBridgeLogger.LOGGER.bridgeAckError(e, bridgeName);
         }
​
         // We don't call failure otherwise failover would be broken with ActiveMQ
         // We let the ExceptionListener to deal with failures
​
         if (connectedSource) {
            try {
               sourceSession.recover();
            } catch (Throwable ignored) {
            }
         }
​
      } finally {
         // Clear the messages
         messages.clear();
​
      }
   }
​
   //......
}