RabbitMQ中Confirm确认与Return返回消息详解（八）

理解Confirm消息确认机制：

　　消息的确认，是指生产者投递消息后，如果Broker收到消息，则会给我们生产这一个应答。

　　生产者进行接收应答，用来确定这条消息是否正常的发送到Broker，这种方式也是消息的可靠性投递的核心保障。

　　

　　如何实现Confirm确认消息？

　　　　第一步：在channel上开启确认模式：channel.confirmSelect()

　　　　第二步：在channel上添加监听：addConfirmListener，监听成功和失败的返回结果，

　　　　　　　　根据具体的结果对消息进行重新发送、或者记录日志等后续处理。

      //生产端代码
      //1 创建ConnectionFactory
         ConnectionFactory connectionFactory = new ConnectionFactory();
         connectionFactory.setHost("127.0.0.1");
         connectionFactory.setPort(5672);
         connectionFactory.setVirtualHost("/");

         //2 获取C    onnection
         Connection connection = connectionFactory.newConnection();

         //3 通过Connection创建一个新的Channel
         Channel channel = connection.createChannel();

         //4 指定我们的消息投递模式: 消息的确认模式
         channel.confirmSelect();

         String exchangeName = "test_confirm_exchange";
         String routingKey = "confirm.save";

         //5 发送一条消息
         String msg = "Hello RabbitMQ Send confirm message!";
         channel.basicPublish(exchangeName, routingKey, null, msg.getBytes());

         //6 添加一个确认监听
         channel.addConfirmListener(new ConfirmListener() {
             @Override
             public void handleNack(long deliveryTag, boolean multiple) throws IOException {
                 System.err.println("-------no ack!-----------");
             }

             @Override
             public void handleAck(long deliveryTag, boolean multiple) throws IOException {
                 System.err.println("-------ack!-----------");
             }
         });    

     //消费端代码
     //1 创建ConnectionFactory
         ConnectionFactory connectionFactory = new ConnectionFactory();
         connectionFactory.setHost("127.0.0.1");
         connectionFactory.setPort(5672);
         connectionFactory.setVirtualHost("/");

         //2 获取C    onnection
         Connection connection = connectionFactory.newConnection();

         //3 通过Connection创建一个新的Channel
         Channel channel = connection.createChannel();

         String exchangeName = "test_confirm_exchange";
         String routingKey = "confirm.#";
         String queueName = "test_confirm_queue";

         //4 声明交换机和队列 然后进行绑定设置, 最后制定路由Key
         channel.exchangeDeclare(exchangeName, "topic", true);
         channel.queueDeclare(queueName, true, false, false, null);
         channel.queueBind(queueName, exchangeName, routingKey);

         //5 创建消费者
         QueueingConsumer queueingConsumer = new QueueingConsumer(channel);
         channel.basicConsume(queueName, true, queueingConsumer);

         while(true){
             Delivery delivery = queueingConsumer.nextDelivery();
             String msg = new String(delivery.getBody());

             System.err.println("消费端: " + msg);
         }

 Return消息机制

　　Return Listener用于处理一些不可路由的消息。

　　我们的消息生产者，通过指定一个Exchange和Routingkey，把消息送到某一个队列中，

　　然后我们的消费者监听队列，进行消息处理操作。

　　但是在某些情况下，如果我们在发送消息的时候，当前的exchange不存在或者指定的路由key路由不到，

　　这个时候我们需要监听这种不可达的消息，就要使用return listener。

　　

　　在基础API中有一个关键的配置项：

　　　　Mandatory：如果为true，则监听会接收到路由不可达的消息，然后进行后续处理，

　　　　　　　　　　如果为false，那么broker端自动删除该消息。（默认false）

　　　　　　　　　　

                 //生产端代码
              ConnectionFactory connectionFactory = new ConnectionFactory();
         connectionFactory.setHost("127.0.0.1");
         connectionFactory.setPort(5672);
         connectionFactory.setVirtualHost("/");

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

         String exchange = "test_return_exchange";
         String routingKey = "return.save";
         String routingKeyError = "abc.save";

         String msg = "Hello RabbitMQ Return Message";

         channel.addReturnListener(new ReturnListener() {
             @Override
             public void handleReturn(int replyCode, String replyText, String exchange,
                     String routingKey, AMQP.BasicProperties properties, byte[] body) throws IOException {

                 System.err.println("---------handle  return----------");
                 System.err.println("replyCode: " + replyCode);
                 System.err.println("replyText: " + replyText);
                 System.err.println("exchange: " + exchange);
                 System.err.println("routingKey: " + routingKey);
                 System.err.println("properties: " + properties);
                 System.err.println("body: " + new String(body));
             }
         });

         channel.basicPublish(exchange, routingKeyError, true, null, msg.getBytes());
             

         //消费端代码
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("127.0.0.1");
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");

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

        String exchangeName = "test_return_exchange";
        String routingKey = "return.#";
        String queueName = "test_return_queue";

        channel.exchangeDeclare(exchangeName, "topic", true, false, null);
        channel.queueDeclare(queueName, true, false, false, null);
        channel.queueBind(queueName, exchangeName, routingKey);

        QueueingConsumer queueingConsumer = new QueueingConsumer(channel);

        channel.basicConsume(queueName, true, queueingConsumer);

        while(true){

            Delivery delivery = queueingConsumer.nextDelivery();
            String msg = new String(delivery.getBody());
            System.err.println("消费者: " + msg);
        }

　　运行结果：