Rabbitmq's priority queue - rabbitmq

Question

Rabbitmq's priority queue mechanism has been tested and will not take effect until the producer is started to publish the message before the consumer is started. How to solve this problem?
**Code snippet**
consumer:
Map<String,Object> args = new HashMap<String,Object>();
args.put("x-max-priority", 10);
channel.queueDeclare(TEST_PRIORITY_QUEUE, true, false, false,args);
//omit... ...
DeliverCallback deliverCallback= (consumerTag, delivery) -> {
try {
String message = new String(delivery.getBody(), "UTF-8");
System.out.println("message="+message);
Thread.sleep(20*1000);
}catch (Exception e) {
e.printStackTrace();
}finally {
channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
}
};
//... ...
producer：
for (int i = 0; i <20; i++) {
String messagelow = "lowLevelMsg";
channel.basicPublish(TEST_EXCHANGE_direct,
"prikey",
new BasicProperties.Builder().priority(1).build(),
messagelow.getBytes());
}
String messagehigh = "HigherLevelMsg";
channel.basicPublish(TEST_EXCHANGE_direct,
"prikey",
new BasicProperties.Builder().priority(9).build(),
messagehigh.getBytes());