Oracle AQ Prioritised JMS messages delivered in reverse priority order

Question

I created an oracle queue like this

execute dbms_aqadm.create_queue_table (
                        queue_table => 'priorityqueue',
                        sort_list => 'PRIORITY,ENQ_TIME',
                        queue_payload_type => 'sys.aq$_jms_map_message',
                        compatible => '8.1.0');
execute dbms_aqadm.create_queue (
                        queue_name => 'priorityqueue',
                        queue_table => 'priorityqueue');
execute dbms_aqadm.start_queue (
                        queue_name => 'priorityqueue');

Then I send messages using spring JMSTemplate like this:

ConnectionFactory connectionFactory = AQjmsFactory.getQueueConnectionFactory(dataSource);
JmsTemplate jmsTemplate = new JmsTemplate(connectionFactory);
jmsTemplate.setExplicitQosEnabled(true);
MessageCreator messageCreator = new MessageCreator() {
        @Override
        public Message createMessage(Session session) throws JMSException {
            MapMessage message = session.createMapMessage();
            // ... set some properties
            message.setJMSPriority(priority);
            return message;
        }
};
jmsTemplate.setPriority(priority);
jmsTemplate.send("priorityqueue", messageCreator);

If I select everything from priorityqueue I can see that the messages get put there with different priorities:

select q_name, msgid, priority, state from priorityqueue;
Q_NAME                         MSGID                              PRIORITY      STATE
PRIORITYQUEUE                  1297D3F58D41208FE05400215A97112C          1          0 
PRIORITYQUEUE                  1297D3F58D43208FE05400215A97112C          9          0 
PRIORITYQUEUE                  1297D3F58D45208FE05400215A97112C          4          0 

Next I consume the messages... not anything fancy - like this:

ConnectionFactory connectionFactory = AQjmsFactory.getQueueConnectionFactory(oracleDataSource);

Connection connection = connectionFactory.createConnection();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
Queue loggerQueue = session.createQueue("priorityqueue");
MessageConsumer consumer = session.createConsumer(loggerQueue);

int count = 0;
while (true) {
    connection.start();
    Message message = consumer.receive(1000);
    if (message == null) {
        break;
    }
    count++;
    System.out.println(count + ".\tPriority [" + message.getJMSPriority() + "]");
}
connection.close();

But the output looks like this:

1. Priority [1]
2. Priority [4]
3. Priority [9]

When it should really be 9, 4, 1.

The documentation for java.jms.Message states explicitly that [t]he JMS API defines ten levels of priority value, with 0 as the lowest priority and 9 as the highest.

What am I doing wrong? I looked into creating the queue with a descending order on the priority but the CREATE_QUEUE_TABLE documentation says that sort_list is [t]he columns to be used as the sort key in ascending order i.e. it doesn't look like descending order is an option.

Also - when sending, I set the priority twice - once on the message and once on the jmsTemplate. Should I really have to do that?

Answer 1

Spring's JmsTemplate doesn't support per-message priorities. You need to subclass JmsTemplate as described in this article: https://aminsblog.wordpress.com/2010/04/27/publishing-qos-priority-enabled-messages-using-spring-jms-template-2/

public class QoSEnabledJmsTemplate extends JmsTemplate {
    protected void doSend(MessageProducer producer, Message message) throws JMSException {
       producer.send(message, getDeliveryMode(), message.getJMSPriority(), getTimeToLive());
    }
}