1.什么是死信（Dead Letter）屠尊？

官方文檔：https://www.rabbitmq.com/dlx.html

一個(gè)消息變成死信的條件有：

1.消費(fèi)被拒絕（basic.reject 或者 basic.nack）捶障，并且參數(shù) requeue = false 時(shí)

2.消息TTL（存活時(shí)間）過(guò)期

3.隊(duì)列達(dá)到最大長(zhǎng)度

rabbitMQ對(duì)于死信消息的處理是：如果配置了死信隊(duì)列蝗砾，成為死信的消息會(huì)被丟進(jìn)死信隊(duì)列，如果沒(méi)有則被丟棄溺忧。

2.配置死信隊(duì)列

死信隊(duì)列不是特殊的隊(duì)列憋飞，它只是綁定在了死信交換機(jī)上而已搭幻，并且死信交換機(jī)也不是特殊的交換機(jī)，它也只是用來(lái)接收死信消息的

哦

一般分為以下步驟：

1.配置業(yè)務(wù)隊(duì)列，綁定到業(yè)務(wù)交換機(jī)上

2.為業(yè)務(wù)隊(duì)列配置死信交換機(jī)和路由

3.配置死信隊(duì)列券勺，綁定到死信交換機(jī)上

模擬其中一種條件來(lái)進(jìn)行實(shí)戰(zhàn)绪钥！

配置類(lèi)：

@Configuration
public class RabbitMQConfig {
    /**
     * 業(yè)務(wù)交換機(jī)
     */
    public static final String BUSINESS_EXCHANGE_NAME = "business.exchange";
    /**
     * 業(yè)務(wù)隊(duì)列
     */
    public static final String BUSINESS_QUEUE_NAME = "business.queue";
    /**
     * 死信交換機(jī)
     */
    public static final String DEAD_EXCHANGE_NAME = "dead.exchange";
    /**
     * 死信隊(duì)列
     */
    public static final String DEAD_QUEUE_NAME = "dead.queue";

    public static final String DEAD_ROUTING_KEY = "dead.routing.key";

    /**
     * 聲明業(yè)務(wù)交換機(jī)
    **/
    @Bean("businessExchange")
    public FanoutExchange businessExchange(){
        return new FanoutExchange(BUSINESS_EXCHANGE_NAME);
    }

    /**
     * 聲明業(yè)務(wù)隊(duì)列
     *
    **/
    @Bean("businessQueue")
    public Queue businessQueue(){
        Map<String, Object> args = new HashMap<>(2);
        //聲明綁定的死信交換機(jī)
        args.put("x-dead-letter-exchange", DEAD_EXCHANGE_NAME);
        //聲明死信路由key
        args.put("x-dead-letter-routing-key", DEAD_ROUTING_KEY);
        return QueueBuilder.durable(BUSINESS_QUEUE_NAME).withArguments(args).build();
    }

    /**
     * 業(yè)務(wù)隊(duì)列綁定到業(yè)務(wù)交換機(jī)
     *
    **/
    @Bean
    public Binding businessBind(@Qualifier("businessQueue")Queue businessQueue,
                                @Qualifier("businessExchange")FanoutExchange businessExchange){
        return BindingBuilder.bind(businessQueue).to(businessExchange);
    }

    /**
     * 聲明死信交換機(jī)
     **/
    @Bean("deadExchange")
    public DirectExchange deadExchange(){
        return new DirectExchange(DEAD_EXCHANGE_NAME);
    }

    /**
     * 聲明死信隊(duì)列
     *
     **/
    @Bean("deadQueue")
    public Queue deadQueue(){
        return new Queue(DEAD_QUEUE_NAME);
    }

    /**
     * 死信隊(duì)列綁定到死信交換機(jī)
     *
     **/
    @Bean
    public Binding deadBind(@Qualifier("deadQueue")Queue deadQueue,
                                @Qualifier("deadExchange")DirectExchange deadExchange){
        return BindingBuilder.bind(deadQueue).to(deadExchange).with(DEAD_ROUTING_KEY);
    }
}

exchange

businessExchange

deadExchange

業(yè)務(wù)隊(duì)列監(jiān)聽(tīng)

@Component
public class BusinessListener {
    Logger logger = LoggerFactory.getLogger(getClass());

    @RabbitListener(queues = RabbitMQConfig.BUSINESS_QUEUE_NAME)
    public void receive(Message message, Channel channel) throws Exception{
        String msg = new String(message.getBody());
        logger.info("收到消息：" + msg);
        if (msg.contains("dead")){
            channel.basicNack(message.getMessageProperties().getDeliveryTag(), false, false);
        }else {
            channel.basicAck(message.getMessageProperties().getDeliveryTag(), false);
        }
    }
}

死信隊(duì)列監(jiān)聽(tīng)

@Component
public class DeadListener {
    Logger logger = LoggerFactory.getLogger(getClass());

    @RabbitListener(queues = RabbitMQConfig.DEAD_QUEUE_NAME)
    public void receive(Message message, Channel channel) throws Exception{
        String msg = new String(message.getBody());
        logger.info("收到消息：" + msg);
    }
}

寫(xiě)一個(gè)controller來(lái)生產(chǎn)消息，方便測(cè)試

@RestController
@RequestMapping("my")
public class MyController {
    @Autowired
    private RabbitTemplate rabbitTemplate;

    @PostMapping("send")
    public void send(@RequestParam("msg")String msg){
        rabbitTemplate.convertSendAndReceive(RabbitMQConfig.BUSINESS_EXCHANGE_NAME,"", msg);
    }
}

發(fā)送一個(gè)消息

發(fā)送消息“msg”

結(jié)果

結(jié)果

發(fā)送消息“deadmsg”

結(jié)果

結(jié)果