1、目標

實現rabbitmq將訊息優先發給閒置的消費者。

2、程式碼

2.1、生產者

private final static String QUEUE_NAME = "hello";

@Test
public void testSend() throws Exception {
    ConnectionFactory factory = new ConnectionFactory();
    factory.setHost("192.168.1.7");
    factory.setUsername("root");
    factory.setPassword("123456"
 
);

    Connection connection = factory.newConnection();
    Channel channel = connection.createChannel();

    channel.queueDeclare(QUEUE_NAME, true, false, false, null);
    for(int i=0;i<20;i++) {
        String message = "Hello "+i;
        channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
        System.out.println(" [1] Sent '"
 
 + message + "'");
    }

    channel.close();
    connection.close();
}

2.2、消費者1

private final static String QUEUE_NAME = "hello";

public static void main(String[] args) throws Exception {
    ConnectionFactory factory = new ConnectionFactory();
    factory.setHost("192.168.1.7");
    factory.setUsername("root"
 
);
    factory.setPassword("123456");

    Connection connection = factory.newConnection();
    final Channel channel = connection.createChannel();

    // 消費者最多接受1條訊息,直到應答後接受新訊息。保證rabbitmq每次將訊息傳送給閒置的消費者
    int prefetchCount = 1;
    channel.basicQos(prefetchCount);

    channel.queueDeclare(QUEUE_NAME, true, false, false, null);
    System.out.println(" [1] Waiting for messages. To exit press CTRL+C");
    Consumer consumer = new DefaultConsumer(channel) {
        @Override
        public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
                byte[] body) throws IOException {
            String message = new String(body, "UTF-8");
            System.out.println(" [1] Received '" + message + "'");
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            // 手動應答
            channel.basicAck(envelope.getDeliveryTag(), false);
        }
    };
    /*
     *  使用公平分發,必須關閉自動應答,使用手動應答
     *  當消費者應答rabbitmq後,rabbitmq將刪除該訊息
     *  保證即時消費者接受訊息後(未應答)中斷,rabbitmq也會將該訊息傳送給其他消費者而不會出現訊息丟失的問題
     */
    boolean autoAck = false;
    channel.basicConsume(QUEUE_NAME, autoAck, consumer);
}

2.2、消費者2

private final static String QUEUE_NAME = "hello";

public static void main(String[] args) throws Exception {
    ConnectionFactory factory = new ConnectionFactory();
    factory.setHost("192.168.1.7");
    factory.setUsername("root");
    factory.setPassword("123456");

    Connection connection = factory.newConnection();
    final Channel channel = connection.createChannel();

    int prefetchCount = 1;
    channel.basicQos(prefetchCount);

    channel.queueDeclare(QUEUE_NAME, true, false, false, null);
    System.out.println(" [2] Waiting for messages. To exit press CTRL+C");
    Consumer consumer = new DefaultConsumer(channel) {
        @Override
        public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
                byte[] body) throws IOException {
            String message = new String(body, "UTF-8");
            System.out.println(" [2] Received '" + message + "'");
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            channel.basicAck(envelope.getDeliveryTag(), false);
        }
    };
    boolean autoAck = false;
    channel.basicConsume(QUEUE_NAME, autoAck, consumer);
}