与Exclusive Consumer相比，Message Groups的对消息分组的粒度更细。具有相同groupId的消息会被投送到同一个消费者，除非这个消费者挂了。

代码示例：

Mesasge message = session.createTextMessage("
     
      hey
     ");// 设置groupIdmessage.setStringProperty("JMSXGroupID", "IBM_NASDAQ_20/4/05");// 设置sequencemessage.setIntProperty("JMSXGroupSeq", -1);producer.send(message);

对应的代码在 org.apache.activemq.broker.region.Queue 中：

// 判断消息能否分发给消费者，返回true表示可以// Subscription 表示消费者，QueueMessageReference 表示消息protected boolean assignMessageGroup(Subscription subscription, QueueMessageReference node)             throws Exception {    // 默认为true    boolean result = true;    // Keep message groups together.    // 获取消息的"JMSXGroupID"属性    String groupId = node.getGroupID();    // 获取消息的"JMSXGroupSeq"属性    int sequence = node.getGroupSequence();    if (groupId != null) {        // MessageGroupMap是一个Map，键是groupId，值是消费者        MessageGroupMap messageGroupOwners = getMessageGroupOwners();        // If we can own the first, then no-one else should own the        // rest.        if (sequence == 1) {            assignGroup(subscription, messageGroupOwners, node, groupId);        } else {            // Make sure that the previous owner is still valid, we may            // need to become the new owner.            ConsumerId groupOwner;            // 根据groupId取出消费者            groupOwner = messageGroupOwners.get(groupId);            if (groupOwner == null) {                assignGroup(subscription, messageGroupOwners, node, groupId);            } else {                if (groupOwner.equals(subscription.getConsumerInfo().getConsumerId())) {                    // A group sequence < 1 is an end of group signal.                    if (sequence < 0) {                        messageGroupOwners.removeGroup(groupId);                        subscription.getConsumerInfo().                        setLastDeliveredSequenceId(subscription.getConsumerInfo().getLastDeliveredSequenceId() - 1);                    }                } else {                    result = false;                }            }        }    }    return result;}// 往MessageGroupMap中插入键值对protected void assignGroup(Subscription subs, MessageGroupMap messageGroupOwners,                         MessageReference n, String groupId) throws IOException {    messageGroupOwners.put(groupId, subs.getConsumerInfo().getConsumerId());    Message message = n.getMessage();    message.setJMSXGroupFirstForConsumer(true);    subs.getConsumerInfo().        setLastDeliveredSequenceId(subs.getConsumerInfo().getLastDeliveredSequenceId() + 1);}