聊聊artemis的persistenceEnabled

public class ConfigurationImpl implements Configuration, Serializable {

   //......

   private boolean persistenceEnabled = ActiveMQDefaultConfiguration.isDefaultPersistenceEnabled();

   public boolean isPersistenceEnabled() {
      return persistenceEnabled;
   }

   public ConfigurationImpl setPersistenceEnabled(final boolean enable) {
      persistenceEnabled = enable;
      return this;
   }

   //......
}  

public class ActiveMQServerImpl implements ActiveMQServer {

   //......

   protected StorageManager createStorageManager() {
      if (configuration.isPersistenceEnabled()) {
         if (configuration.getStoreConfiguration() != null && configuration.getStoreConfiguration().getStoreType() == StoreConfiguration.StoreType.DATABASE) {
            JDBCJournalStorageManager journal = new JDBCJournalStorageManager(configuration, getCriticalAnalyzer(), getScheduledPool(), executorFactory, ioExecutorFactory, shutdownOnCriticalIO);
            this.getCriticalAnalyzer().add(journal);
            return journal;
         } else {
            // Default to File Based Storage Manager, (Legacy default configuration).
            JournalStorageManager journal = new JournalStorageManager(configuration, getCriticalAnalyzer(), executorFactory, scheduledPool, ioExecutorFactory, shutdownOnCriticalIO);
            this.getCriticalAnalyzer().add(journal);
            return journal;
         }
      }
      return new NullStorageManager();
   }

   //......
}

public class PostOfficeImpl implements PostOffice, NotificationListener, BindingsFactory {

   //......

   public void processRoute(final Message message,
                            final RoutingContext context,
                            final boolean direct) throws Exception {
      final List<MessageReference> refs = new ArrayList<>();

      Transaction tx = context.getTransaction();

      Long deliveryTime = message.getScheduledDeliveryTime();

      for (Map.Entry<SimpleString, RouteContextList> entry : context.getContexListing().entrySet()) {
         PagingStore store = pagingManager.getPageStore(entry.getKey());

         if (store != null && storageManager.addToPage(store, message, context.getTransaction(), entry.getValue())) {
            if (message.isLargeMessage()) {
               confirmLargeMessageSend(tx, message);
            }

            // We need to kick delivery so the Queues may check for the cursors case they are empty
            schedulePageDelivery(tx, entry);
            continue;
         }

         for (Queue queue : entry.getValue().getNonDurableQueues()) {
            MessageReference reference = MessageReference.Factory.createReference(message, queue);

            if (deliveryTime != null) {
               reference.setScheduledDeliveryTime(deliveryTime);
            }
            refs.add(reference);

            message.incrementRefCount();
         }

         Iterator<Queue> iter = entry.getValue().getDurableQueues().iterator();

         while (iter.hasNext()) {
            Queue queue = iter.next();

            MessageReference reference = MessageReference.Factory.createReference(message, queue);

            if (context.isAlreadyAcked(context.getAddress(message), queue)) {
               reference.setAlreadyAcked();
               if (tx != null) {
                  queue.acknowledge(tx, reference);
               }
            }

            if (deliveryTime != null) {
               reference.setScheduledDeliveryTime(deliveryTime);
            }
            refs.add(reference);

            if (message.isDurable()) {
               int durableRefCount = message.incrementDurableRefCount();

               if (durableRefCount == 1) {
                  if (tx != null) {
                     storageManager.storeMessageTransactional(tx.getID(), message);
                  } else {
                     storageManager.storeMessage(message);
                  }

                  if (message.isLargeMessage()) {
                     confirmLargeMessageSend(tx, message);
                  }
               }

               if (tx != null) {
                  storageManager.storeReferenceTransactional(tx.getID(), queue.getID(), message.getMessageID());

                  tx.setContainsPersistent();
               } else {
                  storageManager.storeReference(queue.getID(), message.getMessageID(), !iter.hasNext());
               }

               if (deliveryTime != null && deliveryTime > 0) {
                  if (tx != null) {
                     storageManager.updateScheduledDeliveryTimeTransactional(tx.getID(), reference);
                  } else {
                     storageManager.updateScheduledDeliveryTime(reference);
                  }
               }
            }

            message.incrementRefCount();
         }
      }

      if (tx != null) {
         tx.addOperation(new AddOperation(refs));
      } else {
         // This will use the same thread if there are no pending operations
         // avoiding a context switch on this case
         storageManager.afterCompleteOperations(new IOCallback() {
            @Override
            public void onError(final int errorCode, final String errorMessage) {
               ActiveMQServerLogger.LOGGER.ioErrorAddingReferences(errorCode, errorMessage);
            }

            @Override
            public void done() {
               context.processReferences(refs, direct);
            }
         });
      }
   }

   //......
}

public abstract class AbstractJournalStorageManager extends CriticalComponentImpl implements StorageManager {

   //......

   protected Journal messageJournal;

   //......

   public void storeMessage(final Message message) throws Exception {
      if (message.getMessageID() <= 0) {
         // Sanity check only... this shouldn't happen unless there is a bug
         throw ActiveMQMessageBundle.BUNDLE.messageIdNotAssigned();
      }

      readLock();
      try {
         // Note that we don't sync, the add reference that comes immediately after will sync if
         // appropriate

         if (message.isLargeMessage()) {
            messageJournal.appendAddRecord(message.getMessageID(), JournalRecordIds.ADD_LARGE_MESSAGE, LargeMessagePersister.getInstance(), message, false, getContext(false));
         } else {
            messageJournal.appendAddRecord(message.getMessageID(), JournalRecordIds.ADD_MESSAGE_PROTOCOL, message.getPersister(), message, false, getContext(false));
         }
      } finally {
         readUnLock();
      }
   }

   //......
}

public class NullStorageManager implements StorageManager {

   //......

   public void storeMessage(final Message message) throws Exception {
   }

   //......
}