生产者端

目录结构

导入依赖

修改yml

业务逻辑

---

        DLX（Dead Letter Exchange）死信交换机。当消息成为Dead Message时，可以被重新发送到另一个交换机。这个交换机就是死信交换机。这里主要有两个问题：第一是消息如何判断为死信消息，第二则是消息如何从队列中传到死信交换机。

• 消息成为死信消息的三种情况

  • 队列消息长度达到限制

  • 消费者拒收消息（basicNack()或basicReject），且不把消息重新放回队列（basicNack()方法第三个参数）

  • 消息TTL过期   下面我演示的就是这种情况

• 队列绑定死信交换机

  • 给队列设置参数：x-dead-letter-exchange 和 x-dead-letter-routing-key

生产者端

目录结构

导入依赖

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-amqp</artifactId>
        <version>2.5.0</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
</dependencies>

修改yml

spring:
  rabbitmq:
    host: localhost
    port: 5672
    username: guest
    password: guest
    publisher-returns: true # 开启退回回调
    #三个类型：none默认不开启确认回调 correlated开启确认回调
    #simple也会确认回调 还会调用waitForConfirms()方法或waitForConfirmsOrDie()方法
    publisher-confirm-type: correlated # 开启确认回调

业务逻辑

/**
 * 定义交换机与队列的Bean 并且使之绑定
 * 生产者 -> 普通交换机 -> 普通队列 -> 消费者1
 *                        |
 *                        -> 死信交换机 -> 死信队列 -> 消费者2
 * 需要两个交换机两个队列、三个路由键。两个普通之间我用了"test.#" 
 * 普通与死信之间用了"test.dead.heHe" 两个死信之间用了"test.dead.#" 生产的消息用的就是"test.dead.heHe"
 */
@Component
public class RabbitMQConfig {

    public static final String EXCHANGE_NAME = "test_exchange_name";
    public static final String QUEUE_NAME = "test_queue_name";
    public static final String DEAD_EXCHANGE_NAME = "dead_exchange_name";
    public static final String DEAD_QUEUE_NAME = "dead_queue_name";

    @Bean("testExchange")
    public Exchange testExchange(){
        return ExchangeBuilder.topicExchange(EXCHANGE_NAME).durable(true).build();
    }

    @Bean("deadExchange")
    public Exchange deadExchange(){
        return ExchangeBuilder.topicExchange(DEAD_EXCHANGE_NAME).durable(true).build();
    }

    //普通队列绑定死信交换机并且带上路由键 为了实现死信消息于是配置队列TTL
    @Bean("testQueue")
    public Queue testQueue(){
        return QueueBuilder.durable(QUEUE_NAME).ttl(5000).deadLetterExchange(DEAD_EXCHANGE_NAME)
                .deadLetterRoutingKey("test.dead.heHe").build();
    }

    @Bean("deadQueue")
    public Queue deadQueue(){
        return QueueBuilder.durable(DEAD_QUEUE_NAME).build();
    }

    @Bean
    public Binding link(@Qualifier("testExchange") Exchange exchange,
                        @Qualifier("testQueue") Queue queue){
        return BindingBuilder.bind(queue).to(exchange).with("test.#").noargs();
    }

    @Bean
    public Binding deadLink(@Qualifier("deadExchange") Exchange exchange,
                            @Qualifier("deadQueue") Queue queue){
        return BindingBuilder.bind(queue).to(exchange).with("test.dead.#").noargs();
    }
}

@SpringBootTest
@RunWith(SpringRunner.class)
class RabbitmqProducerApplicationTests {

    @Autowired
    private RabbitTemplate rabbitTemplate;

    @Test
    void testProducer() {
        rabbitTemplate.setConfirmCallback(new RabbitTemplate.ConfirmCallback() {
            @Override
            public void confirm(CorrelationData correlationData, boolean b, String s) {
                if(b) System.out.println("交换机成功接受到了消息");
                else System.out.println("消息失败原因" + s);
            }
        });
        // 设置交换机处理失败消息的模式
        // true:消息到达不了队列时 会将消息重新返回给生产者 false:消息到达不了队列直接丢弃
        rabbitTemplate.setMandatory(true);
        rabbitTemplate.setReturnCallback(new RabbitTemplate.ReturnCallback() {
            @Override
            public void returnedMessage(Message message, int i, String s, String s1, String s2) {
                System.out.println("队列接受不到交换机的消息进行了失败回调");
            }
        });
        for(int i = 0; i < 10; ++i){
            rabbitTemplate.convertAndSend(RabbitMQConfig.EXCHANGE_NAME,"test.dead.heHe","HelloWorld");
        }
    }
}