• RabbitMQ死信队列原理与项目代码示例

    1、产生死信消息的原因

    当在消费消息时，如果队列里的消息出现以下情况，那么该消息将成为一条死信消息：

    • 当一条消息被使用 channel.basicNack方法 或 channel.basicReject方法所nack响应 ，并且此时requeue 属性被设置为false。

    • 消息在队列的存活时间超过设置的生存时间（TTL)时间。

    • 消息队列的消息数量超过了设置的最大队列长度。

    死信队列（DLQ）非常简单，就一个普通的队列，只不过它是和死信交换机绑定的而已，在声明队列的时候，通过x-dead-letter-exchange参数和x-dead-letter-routing-key指定死信交换机以及死信路由键即可。

    • 参数dead-letter-exchange：指定死信交换机。

    • 参数dead-letter-routing-key：指定死信路由键，用于绑定死信交换机和死信队列。

    2、代码实现

    pom.xml

    plugins {
	id 'java'
	id 'org.springframework.boot' version '3.1.1'
	id 'io.spring.dependency-management' version '1.1.0'
}

group = 'com.kexuexiong'
version = '0.0.1-SNAPSHOT'

java {
	sourceCompatibility = '17'
}

configurations {
	compileOnly {
		extendsFrom annotationProcessor
	}
}

repositories {
//	mavenCentral()
	maven {
		url 'https://maven.aliyun.com/repository/public'
	}
}

dependencies {
	implementation 'org.springframework.boot:spring-boot-starter-jdbc'
	implementation 'org.springframework.boot:spring-boot-starter-validation'
	implementation 'org.springframework.boot:spring-boot-starter-web'
	implementation 'org.mybatis.spring.boot:mybatis-spring-boot-starter:3.0.2'
	compileOnly 'org.projectlombok:lombok'
	runtimeOnly 'com.mysql:mysql-connector-j'
	annotationProcessor 'org.projectlombok:lombok'
	testImplementation 'org.springframework.boot:spring-boot-starter-test'
	testImplementation 'org.mybatis.spring.boot:mybatis-spring-boot-starter-test:3.0.2'
	// https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-amqp
	implementation 'org.springframework.boot:spring-boot-starter-amqp'
	implementation 'cn.hutool:hutool-all:5.8.16'
}

tasks.named('test') {
	useJUnitPlatform()
}


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    yml配置文件：
    搭建的是RabbitMQ集群：192.168.49.10:5672,192.168.49.9:5672,192.168.49.11:5672
    详细搭建过程可以参考往期中的RabbitMQ集群搭建。

    server:
  port: 8014

spring:
  rabbitmq:
    username: admin
    password: 123456
    dynamic: true
#    port: 5672
#    host: 192.168.49.9
    addresses: 192.168.49.10:5672,192.168.49.9:5672,192.168.49.11:5672
    publisher-confirm-type: correlated
    publisher-returns: true
  application:
    name: shushan
  datasource:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://ip/shushan
      username: root
      password: 
      hikari:
        minimum-idle: 10
        maximum-pool-size: 20
        idle-timeout: 50000
        max-lifetime: 540000
        connection-test-query: select 1
        connection-timeout: 600000

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    常量文件：

    package com.kexuexiong.shushan.common.mq;

import javax.swing.plaf.PanelUI;

public class MqConstant {

    public final static String demoDirectQueue = "demoDirectQueue";

    public final static String demoDirectExchange = "demoDirectExchange";

    public final static String demoDirectRouting = "demoDirectRouting";

    public final static String lonelyDirectExchange = "lonelyDirectExchange";

    public final static String topicExchange = "topicExchange";

    public final static String BIG_CAR_TOPIC = "topic.big_car";

    public final static String SMALL_CAR_TOPIC = "topic.small_car";

    public final static String TOPIC_ALL = "topic.#";

    public final static String FANOUT_A = "fanout.A";

    public final static String FANOUT_B = "fanout_B";

    public final static String FANOUT_C = "fanout_c";

    public final static String FANOUT_EXCHANGE = "fanoutExchange";

    public final static String DEAD_LETTER_EXCHANGE = "dead.letter.exchange";

    public final static String DEAD_LETTER_QUEUE = "dead.letter.queue";

    public final static String DEAD_LETTER_ROUTING_KEY = "dead.letter.routing.key";

    public final static String BUSINESS_QUEUE = "business.queue";

    public final static String BUSINESS_ROUTING_KEY = "business.routing.key";

    public final static String BUSINESS_EXCHANGE = "business.exchange";


}


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    RabbitMQ配置文件：

    package com.kexuexiong.shushan.common.mq;


import org.springframework.amqp.core.*;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.HashMap;


@Configuration
public class DirectDLXRabbitConfig {

    @Bean
    public Queue businessDirectQueue() {
        HashMap<String, Object> args = new HashMap<>();
        args.put("x-dead-letter-exchange",MqConstant.DEAD_LETTER_EXCHANGE);//设置死信交换机
        args.put("x-dead-letter-routing-key",MqConstant.DEAD_LETTER_ROUTING_KEY);
        return QueueBuilder.durable(MqConstant.BUSINESS_QUEUE).withArguments(args).build();
    }

    @Bean
    DirectExchange businessDirectExchange() {
        return new DirectExchange(MqConstant.BUSINESS_EXCHANGE, true, false);
    }

    @Bean
    DirectExchange deadLetterDirectExchange() {
        return new DirectExchange(MqConstant.DEAD_LETTER_EXCHANGE, true, false);
    }

    @Bean
    public Queue deadLetterDirectQueue() {
        return new Queue(MqConstant.DEAD_LETTER_QUEUE, true, false, false);
    }

    @Bean
    Binding deadLetterBingingDirect() {
        return BindingBuilder.bind(deadLetterDirectQueue()).to(deadLetterDirectExchange()).with(MqConstant.DEAD_LETTER_ROUTING_KEY);
    }


    @Bean
    Binding businessBingingDirect() {
        return BindingBuilder.bind(businessDirectQueue()).to(businessDirectExchange()).with(MqConstant.BUSINESS_ROUTING_KEY);
    }

}


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    队列绑定死信交换机：
    在这里插入图片描述

    生产者：

    package com.kexuexiong.shushan.controller.mq;

import cn.hutool.core.date.DateUtil;
import cn.hutool.core.util.RandomUtil;
import com.kexuexiong.shushan.common.mq.MqConstant;
import com.kexuexiong.shushan.controller.BaseController;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.MessagePostProcessor;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;

@Slf4j
@RestController
@RequestMapping("/mq/")
public class MqController extends BaseController {

    @Autowired
    RabbitTemplate rabbitTemplate;

    @GetMapping("/deadLetterSendDirectMessage")
    public String deadLetterSendDirectMessage(){

        String msgId = UUID.randomUUID().toString();
        String msg = "demo msg ,dead letter!!";
        String createTime = DateUtil.format(new Date(),"YYYY-MM-dd HH:mm:ss");

        Map<String,Object> map = new HashMap();
        map.put("msgId",msgId);
        map.put("msg",msg);
        map.put("createTime",createTime);

        rabbitTemplate.convertAndSend(MqConstant.BUSINESS_EXCHANGE,MqConstant.BUSINESS_ROUTING_KEY,map);

        return "ok";
    }

    @GetMapping("/deadLetterTimeOutSendDirectMessage")
    public String deadLetterTimeOutSendDirectMessage(){

        String msgId = UUID.randomUUID().toString();
        String msg = "demo msg ,dead letter!!";
        String createTime = DateUtil.format(new Date(),"YYYY-MM-dd HH:mm:ss");
        log.info("msg time :" +createTime);
        Map<String,Object> map = new HashMap();
        map.put("msgId",msgId);
        map.put("msg",msg);
        map.put("createTime",createTime);
        Integer randomInt = RandomUtil.randomInt(30000);
        map.put("randomTime",randomInt);
        MessagePostProcessor messagePostProcessor = message -> {
            // 设置消息过期时间为5秒
            message.getMessageProperties().setExpiration("30000");
            return message;
        };

        rabbitTemplate.convertAndSend(MqConstant.BUSINESS_EXCHANGE,MqConstant.BUSINESS_ROUTING_KEY,map,messagePostProcessor);

        return "ok";
    }

   
}


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    消费者：

    package com.kexuexiong.shushan.common.mq;

import org.springframework.amqp.core.AcknowledgeMode;
import org.springframework.amqp.rabbit.connection.CachingConnectionFactory;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MessageListenerConfig {

    @Autowired
    private CachingConnectionFactory connectionFactory;

    @Autowired
    private AckReceiver ackReceiver;

    @Bean
    public SimpleMessageListenerContainer simpleMessageListenerContainer() {
        SimpleMessageListenerContainer simpleMessageListenerContainer = new SimpleMessageListenerContainer(connectionFactory);

        simpleMessageListenerContainer.setConcurrentConsumers(2);
        simpleMessageListenerContainer.setMaxConcurrentConsumers(2);
        simpleMessageListenerContainer.setAcknowledgeMode(AcknowledgeMode.MANUAL);
        //,MqConstant.demoDirectQueue, MqConstant.FANOUT_A, MqConstant.BIG_CAR_TOPIC

        simpleMessageListenerContainer.setQueueNames(MqConstant.DEAD_LETTER_QUEUE);

        simpleMessageListenerContainer.setMessageListener(ackReceiver);

        return simpleMessageListenerContainer;
    }

}


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    AckReceiver：

    package com.kexuexiong.shushan.common.mq;

import com.rabbitmq.client.Channel;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.listener.api.ChannelAwareMessageListener;
import org.springframework.stereotype.Component;

import java.io.ByteArrayInputStream;
import java.io.ObjectInputStream;
import java.util.Map;
import java.util.Objects;

@Slf4j
@Component
public class AckReceiver implements ChannelAwareMessageListener {
    @Override
    public void onMessage(Message message, Channel channel) throws Exception {
        long deliveryTag = message.getMessageProperties().getDeliveryTag();
        byte[] messageBody = message.getBody();
        try (ObjectInputStream inputStream = new ObjectInputStream(new ByteArrayInputStream(messageBody));) {

            Map<String, String> msg = (Map<String, String>) inputStream.readObject();
            log.info(message.getMessageProperties().getConsumerQueue()+"-ack Receiver :" + msg);
            log.info("header msg :"+message.getMessageProperties().getHeaders());
            if(Objects.equals(message.getMessageProperties().getConsumerQueue(),MqConstant.BUSINESS_QUEUE)){
             //拒绝
                channel.basicNack(deliveryTag,false,false);

            }else if(Objects.equals(message.getMessageProperties().getConsumerQueue(),MqConstant.DEAD_LETTER_QUEUE)){
                channel.basicAck(deliveryTag, true);
            }else {
                channel.basicAck(deliveryTag, true);
            }

        } catch (Exception e) {
            channel.basicReject(deliveryTag, false);
            log.error(e.getMessage());
        }
    }
}


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    测试：

    1、当一条消息被使用 channel.basicNack方法 或 channel.basicReject方法所nack响应 ，并且此时requeue 属性被设置为false

    在这里插入图片描述

    2023-10-11T16:18:13.124+08:00  INFO 28104 --- [enerContainer-2] c.k.shushan.common.mq.AckReceiver        : business.queue-ack Receiver :{msg=demo msg ,dead letter!!, createTime=2023-10-11 16:18:13, msgId=9b31b4b3-c58f-47bd-8b27-cac4f53ae120}
2023-10-11T16:18:13.125+08:00  INFO 28104 --- [enerContainer-2] c.k.shushan.common.mq.AckReceiver        : header msg :{spring_listener_return_correlation=995de3d2-d5a8-42fe-91e6-992fd485d20d}
2023-10-11T16:18:13.125+08:00  INFO 28104 --- [nectionFactory1] c.k.shushan.common.config.RabbitConfig   : confirmCallback  data: null
2023-10-11T16:18:13.125+08:00  INFO 28104 --- [nectionFactory1] c.k.shushan.common.config.RabbitConfig   : confirmCallback ack :true
2023-10-11T16:18:13.125+08:00  INFO 28104 --- [nectionFactory1] c.k.shushan.common.config.RabbitConfig   : confirmCallback cause :null
2023-10-11T16:18:13.127+08:00  INFO 28104 --- [enerContainer-1] c.k.shushan.common.mq.AckReceiver        : dead.letter.queue-ack Receiver :{msg=demo msg ,dead letter!!, createTime=2023-10-11 16:18:13, msgId=9b31b4b3-c58f-47bd-8b27-cac4f53ae120}
2023-10-11T16:18:13.127+08:00  INFO 28104 --- [enerContainer-1] c.k.shushan.common.mq.AckReceiver        : header msg :{spring_listener_return_correlation=995de3d2-d5a8-42fe-91e6-992fd485d20d, x-first-death-exchange=business.exchange, x-death=[{reason=rejected, count=1, exchange=business.exchange, time=Wed Oct 11 16:18:14 CST 2023, routing-keys=[business.routing.key], queue=business.queue}], x-first-death-reason=rejected, x-first-death-queue=business.queue}


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    if(Objects.equals(message.getMessageProperties().getConsumerQueue(),MqConstant.BUSINESS_QUEUE)){
             //拒绝
                channel.basicNack(deliveryTag,false,false);

  }

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    消费者代码中拒绝消费，然后消息被路由到死信队列中。

    {spring_listener_return_correlation=995de3d2-d5a8-42fe-91e6-992fd485d20d, x-first-death-exchange=business.exchange, x-death=[{reason=rejected, count=1, exchange=business.exchange, time=Wed Oct 11 16:18:14 CST 2023, routing-keys=[business.routing.key], queue=business.queue}], x-first-death-reason=rejected, x-first-death-queue=business.queue}

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    reason为rejected，并记录原交换机 exchange=business.exchange。

    2、消息在队列的存活时间超过设置的生存时间（TTL)时间

    将消费者中的MqConstant.BUSINESS_QUEUE去掉，后测试。
    设置消息过期时间可以在队列中设置：增加参数x-message-ttl；

     @Bean("businessQueue")
    public Queue businessQueue() {
        Map<String, Object> args = new HashMap<>(16);
        // 设置当前队列绑定的死信交换机
        args.put("x-dead-letter-exchange", DEAD_LETTER_EXCHANGE);
        // 设置当前队列的死信路由key
        args.put("x-dead-letter-routing-key", DEAD_LETTER_ROUTING_KEY);
        // 设置消息的过期时间 单位：ms（毫秒）
        args.put("x-message-ttl", 5000);
        return QueueBuilder.durable(BUSINESS_QUEUE).withArguments(args).build();
    }

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    也可以针对每个消息进行设置过期时间：

      @GetMapping("/deadLetterTimeOutSendDirectMessage")
    public String deadLetterTimeOutSendDirectMessage(){

        String msgId = UUID.randomUUID().toString();
        String msg = "demo msg ,dead letter!!";
        String createTime = DateUtil.format(new Date(),"YYYY-MM-dd HH:mm:ss");
        log.info("msg time :" +createTime);
        Map<String,Object> map = new HashMap();
        map.put("msgId",msgId);
        map.put("msg",msg);
        map.put("createTime",createTime);
        Integer randomInt = RandomUtil.randomInt(30000);
        map.put("randomTime",randomInt);
        MessagePostProcessor messagePostProcessor = message -> {
            // 设置消息过期时间为5秒
            message.getMessageProperties().setExpiration("30000");
            return message;
        };

        rabbitTemplate.convertAndSend(MqConstant.BUSINESS_EXCHANGE,MqConstant.BUSINESS_ROUTING_KEY,map,messagePostProcessor);

        return "ok";
    }

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    在这里插入图片描述
    测试：
    在这里插入图片描述

    2023-10-11T16:28:49.052+08:00  INFO 25848 --- [nio-8014-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2023-10-11T16:28:49.052+08:00  INFO 25848 --- [nio-8014-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2023-10-11T16:28:49.053+08:00  INFO 25848 --- [nio-8014-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 1 ms
2023-10-11T16:28:49.099+08:00  INFO 25848 --- [nio-8014-exec-1] c.k.shushan.controller.mq.MqController   : msg time :2023-10-11 16:28:49
2023-10-11T16:28:49.120+08:00  INFO 25848 --- [nectionFactory1] c.k.shushan.common.config.RabbitConfig   : confirmCallback  data: null
2023-10-11T16:28:49.121+08:00  INFO 25848 --- [nectionFactory1] c.k.shushan.common.config.RabbitConfig   : confirmCallback ack :true
2023-10-11T16:28:49.121+08:00  INFO 25848 --- [nectionFactory1] c.k.shushan.common.config.RabbitConfig   : confirmCallback cause :null
2023-10-11T16:29:19.123+08:00  INFO 25848 --- [enerContainer-1] c.k.shushan.common.mq.AckReceiver        : dead.letter.queue-ack Receiver :{msg=demo msg ,dead letter!!, randomTime=22235, createTime=2023-10-11 16:28:49, msgId=4793dd5c-70c2-4c2f-a6ae-cdc6663e0b05}
2023-10-11T16:29:19.123+08:00  INFO 25848 --- [enerContainer-1] c.k.shushan.common.mq.AckReceiver        : header msg :{spring_listener_return_correlation=22fdc49f-30da-4524-9fc8-d4f69eb4c2c3, x-first-death-exchange=business.exchange, x-death=[{reason=expired, original-expiration=30000, count=1, exchange=business.exchange, time=Wed Oct 11 16:29:20 CST 2023, routing-keys=[business.routing.key], queue=business.queue}], x-first-death-reason=expired, x-first-death-queue=business.queue}


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    在这里插入图片描述
    30秒过期，进入死信队列，然后被消费。

    3、 消息队列的消息数量超过了设置的最大队列长度

    修改RabbitMQ配置文件，创建businessDirectQueue时增加x-max-length设置容量的参数。

    package com.kexuexiong.shushan.common.mq;


import org.springframework.amqp.core.*;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.HashMap;


@Configuration
public class DirectDLXRabbitConfig {

    @Bean
    public Queue businessDirectQueue() {
        HashMap<String, Object> args = new HashMap<>();
        args.put("x-dead-letter-exchange",MqConstant.DEAD_LETTER_EXCHANGE);
        args.put("x-dead-letter-routing-key",MqConstant.DEAD_LETTER_ROUTING_KEY);
        args.put("x-max-length", 3);
        return QueueBuilder.durable(MqConstant.BUSINESS_QUEUE).withArguments(args).build();
    }

    @Bean
    DirectExchange businessDirectExchange() {
        return new DirectExchange(MqConstant.BUSINESS_EXCHANGE, true, false);
    }

    @Bean
    DirectExchange deadLetterDirectExchange() {
        return new DirectExchange(MqConstant.DEAD_LETTER_EXCHANGE, true, false);
    }

    @Bean
    public Queue deadLetterDirectQueue() {
        return new Queue(MqConstant.DEAD_LETTER_QUEUE, true, false, false);
    }

    @Bean
    Binding deadLetterBingingDirect() {
        return BindingBuilder.bind(deadLetterDirectQueue()).to(deadLetterDirectExchange()).with(MqConstant.DEAD_LETTER_ROUTING_KEY);
    }


    @Bean
    Binding businessBingingDirect() {
        return BindingBuilder.bind(businessDirectQueue()).to(businessDirectExchange()).with(MqConstant.BUSINESS_ROUTING_KEY);
    }

}


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    在这里插入图片描述

    测试：
    在这里插入图片描述

    在这里插入图片描述
    第三次请求的结果：
    在这里插入图片描述

    第四次请求结果：
    在这里插入图片描述
    控制台输出，死信队列接收到消息。

    2023-10-11T16:46:54.783+08:00  INFO 20444 --- [nectionFactory2] c.k.shushan.common.config.RabbitConfig   : confirmCallback  data: null
2023-10-11T16:46:54.783+08:00  INFO 20444 --- [nectionFactory2] c.k.shushan.common.config.RabbitConfig   : confirmCallback ack :true
2023-10-11T16:46:54.783+08:00  INFO 20444 --- [nectionFactory2] c.k.shushan.common.config.RabbitConfig   : confirmCallback cause :null
2023-10-11T16:46:54.787+08:00  INFO 20444 --- [enerContainer-1] c.k.shushan.common.mq.AckReceiver        : dead.letter.queue-ack Receiver :{msg=demo msg ,dead letter!!, createTime=2023-10-11 16:44:35, msgId=db7d2d7f-12a0-4ca4-9e92-81758cda436e}
2023-10-11T16:46:54.787+08:00  INFO 20444 --- [enerContainer-1] c.k.shushan.common.mq.AckReceiver        : header msg :{spring_listener_return_correlation=e2a1871a-7765-43ee-b44c-d80d0ac6323c, x-first-death-exchange=business.exchange, x-death=[{reason=maxlen, count=1, exchange=business.exchange, time=Wed Oct 11 16:46:56 CST 2023, routing-keys=[business.routing.key], queue=business.queue}], x-first-death-reason=maxlen, x-first-death-queue=business.queue}


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    到这里三种情况都介绍完了，总体来讲RabbitMQ的死信队列还是很简单的。但是它作用还是很强大的，可以用于实现延时消息，订单到时取消等。

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  • 原文地址：https://blog.csdn.net/qq_22744093/article/details/133772586