一、应用场景

• 业务中心根据业务需求向特定用户发送消息；发送前不确定由哪个用户接收

• 特定用户接收特定消息；用户可以退出，再切换别的用户登录，用户登录后只接收与自已对应的消息

二、总体要求

项目要足够稳健，消息不能丢失

• 交换机、队列、消息持久化

• 队列有容量限制；如：3000

• 消息发送后需要确认（非自动确认）

• 未发送成功的消息，由缓存保存，定时重发

• 交换机收到消息，但无法投递时，转发至备份交换机，再广播至对应队列

三、架构图

四、安装RabbitMQ

参考如下三篇文章

• 【RabbitMQ】RabbitMQ入门及安装

• 【RabbitMQ】Docker中安装RabbitMQ

• 【图文详解】RabbitMQ集群搭建、镜像队列、负载均衡HAProxy、故障转移Keepalived

五、搭建SpringBoot项目

• java1.8

• spring-boot 2.6.7

1、依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.7</version>
    </parent>

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.tuwer</groupId>
    <artifactId>mq</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <!-- amqp-client -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-amqp</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- amqp-client Java原生依赖 -->
<!--        <dependency>
            <groupId>com.rabbitmq</groupId>
            <artifactId>amqp-client</artifactId>
            <version>5.14.2</version>
        </dependency>-->
        <!-- hutool-all -->
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.8.2</version>
        </dependency>
        <!-- jackson -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.13.3</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
            <version>2.13.3</version>
        </dependency>
        <dependency>
            <groupId>jakarta.json</groupId>
            <artifactId>jakarta.json-api</artifactId>
            <version>2.0.1</version>
        </dependency>
        <!-- fastjson -->
        <dependency>
            <groupId>com.alibaba.fastjson2</groupId>
            <artifactId>fastjson2</artifactId>
            <version>2.0.3</version>
        </dependency>
        <!-- lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
        </dependency>
        <!-- 工具类 -->
        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>2.6</version>
        </dependency>
        <!-- 测试 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.amqp</groupId>
            <artifactId>spring-rabbit-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

2、application.yml

spring:
  rabbitmq:
    host: 192.168.3.174
    port: 5672
    username: admin
    password: admin
    virtual-host: /
    # 交换机接收确认
    publisher-confirm-type: correlated
    # 交换机回退消息
    #publisher-returns: true

2、启动类

package com.tuwer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 * @author 土味儿
 * Date 2023/1/4
 * @version 1.0
 */
@SpringBootApplication
public class MqApp {
    public static void main(String[] args) {
        SpringApplication.run(MqApp.class, args);
    }
}

3、基础类

3.1、常量类

package com.tuwer.constant;

/**
 * <p>系统常量类</p>
 *
 * @author 土味儿
 * Date 2023/1/4
 * @version 1.0
 */
public class Constants {
    /**
     * 队列容量、通道预取值
     * 队列容量应根据项目需要，设置合适的值；
     * 本案例中为了测试方便设为5
     */
    public static final int QUEUE_CAPACITY = 5;
    public static final int PRE_FETCH_SIZE = 10;

    /**
     * 交换机
     */
    public static final String NORMAL_EXCHANGE = "normal_exchange";
    public static final String BACKUP_EXCHANGE = "backup_exchange";

    /**
     * 队列
     */
    public static final String BACKUP_QUEUE = "backup_queue";
}

3.2、雪花算法工具类

获取Long型id：SnowflakeUtil.getInstance().nextId()

package com.tuwer.util;

import lombok.extern.slf4j.Slf4j;

import java.text.MessageFormat;

/**
 * <p>雪花算法工具类</p>
 *
 * @author 土味儿
 * Date 2022/6/2
 * @version 1.0
 */
@Slf4j
@SuppressWarnings("all")
public class SnowflakeUtil {
    // ==============================Fields===========================================
    /**
     * 开始时间戳 (2000-01-01 00:00:00)
     */
    private static final long TWEPOCH = 946656000000L;

    /**
     * 机器id所占的位数 5
     */
    private static final long WORKER_ID_BITS = 5L;

    /**
     * 数据标识id所占的位数 5
     */
    private static final long DATA_CENTER_ID_BITS = 5L;

    /**
     * 支持的最大机器id，结果是 31
     */
    private static final long MAX_WORKER_ID = ~(-1L << WORKER_ID_BITS);

    /**
     * 支持的最大数据标识id，结果是 31
     */
    private static final long MAX_DATA_CENTER_ID = ~(-1L << DATA_CENTER_ID_BITS);

    /**
     * 序列在id中占的位数
     */
    private static final long SEQUENCE_BITS = 12L;

    /**
     * 机器ID向左移12位
     */
    private static final long WORKER_ID_SHIFT = SEQUENCE_BITS;

    /**
     * 数据标识id向左移17位(12+5)
     */
    private static final long DATA_CENTER_ID_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS;

    /**
     * 时间戳向左移22位(5+5+12)
     */
    private static final long TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATA_CENTER_ID_BITS;

    /**
     * 生成序列的掩码，这里为4095 (0b111111111111=0xfff=4095)
     */
    private static final long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS);

    /**
     * 步长 1024
     */
    private static final long STEP_SIZE = 1024;

    /**
     * unsigned int max value
     */
    private static final long UINT_MAX_VALUE = 0xffffffffL;

    /**
     * 工作机器ID(0~31)
     */
    private long workerId;

    /**
     * 工作机器ID 计数器
     */
    private long workerIdFlags = 0L;

    /**
     * 数据中心ID(0~31)
     */
    private long dataCenterId;

    /**
     * 数据中心ID 计数器
     */
    private long dataCenterIdFlags = 0L;

    /**
     * 毫秒内序列(0~4095)
     */
    private long sequence = 0L;

    /**
     * 毫秒内序列基数[0|1024|2048|3072]
     */
    private long basicSequence = 0L;

    /**
     * 上次生成ID的时间戳
     */
    private long lastTimestamp = -1L;

    /**
     * 工作模式
     */
    private final WorkMode workMode;

    public enum WorkMode {NON_SHARED, RATE_1024, RATE_4096;}

    //==============================单例模式（静态内部类）=====================================
    private static class InnerClass{
        private static final SnowflakeUtil INNER_DEMO = new SnowflakeUtil();
    }
    public static SnowflakeUtil getInstance(){
        return InnerClass.INNER_DEMO;
    }

    //==============================Constructors=====================================

    public SnowflakeUtil() {
        this(0, 0, WorkMode.RATE_4096);
    }

    /**
     * 构造函数
     *
     * @param workerId     工作ID (0~31)
     * @param dataCenterId 数据中心ID (0~31)
     */
    public SnowflakeUtil(long workerId, long dataCenterId) {
        this(workerId, dataCenterId, WorkMode.RATE_4096);
    }

    /**
     * 构造函数
     *
     * @param workerId     工作ID (0~31)
     * @param dataCenterId 数据中心ID (0~31)
     * @param workMode     工作模式
     */
    public SnowflakeUtil(long workerId, long dataCenterId, WorkMode workMode) {
        this.workMode = workMode;
        if (workerId > MAX_WORKER_ID || workerId < 0) {
            throw new IllegalArgumentException(MessageFormat.format("worker Id can't be greater than {0} or less than 0", MAX_WORKER_ID));
        }
        if (dataCenterId > MAX_DATA_CENTER_ID || dataCenterId < 0) {
            throw new IllegalArgumentException(MessageFormat.format("datacenter Id can't be greater than {0} or less than 0", MAX_DATA_CENTER_ID));
        }
        this.workerId = workerId;
        this.workerIdFlags = setSpecifiedBitTo1(this.workerIdFlags, this.workerId);
        this.dataCenterId = dataCenterId;
        this.dataCenterIdFlags = setSpecifiedBitTo1(this.dataCenterIdFlags, this.dataCenterId);
    }

    // ==============================Methods==========================================

    /**
     * 获取机器id
     *
     * @return 所属机器的id
     */
    public long getWorkerId() {
        return workerId;
    }

    /**
     * 获取数据中心id
     *
     * @return 所属数据中心id
     */
    public long getDataCenterId() {
        return dataCenterId;
    }

    /**
     * 获得下一个ID (该方法是线程安全的)
     *
     * @return SnowflakeId
     */
    public synchronized long nextId() {
        long timestamp = timeGen();
        //如果当前时间小于上一次ID生成的时间戳，说明系统时钟回退过这个时候应当抛出异常
        if (timestamp < this.lastTimestamp) {
            if (timestamp > TWEPOCH) {
                if (WorkMode.NON_SHARED == this.workMode) {
                    nonSharedClockBackwards(timestamp);
                } else if (WorkMode.RATE_1024 == this.workMode) {
                    rate1024ClockBackwards(timestamp);
                } else {
                    throw new RuntimeException(MessageFormat.format("Clock moved backwards. Refusing to generate id for {0} milliseconds", lastTimestamp - timestamp));
                }
            } else {
                throw new RuntimeException(MessageFormat.format("Clock moved backwards. Refusing to generate id for {0} milliseconds", lastTimestamp - timestamp));
            }
        }
        //如果是同一时间生成的，则进行毫秒内序列
        if (this.lastTimestamp == timestamp) {
            this.sequence = (this.sequence + 1) & SEQUENCE_MASK;
            //毫秒内序列溢出
            if (this.sequence == 0) {
                //阻塞到下一个毫秒,获得新的时间戳
                timestamp = tilNextMillis(this.lastTimestamp);
            }
        }
        //时间戳改变，毫秒内序列重置
        else {
            this.sequence = this.basicSequence;
        }
        //上次生成ID的时间戳
        this.lastTimestamp = timestamp;
        //移位并通过或运算拼到一起组成64位的ID
        return ((timestamp - TWEPOCH) << TIMESTAMP_LEFT_SHIFT)
                | (this.dataCenterId << DATA_CENTER_ID_SHIFT)
                | (this.workerId << WORKER_ID_SHIFT)
                | this.sequence;
    }

    /**
     * 阻塞到下一个毫秒，直到获得新的时间戳
     *
     * @param lastTimestamp 上次生成ID的时间戳
     * @return 当前时间戳
     */
    protected long tilNextMillis(long lastTimestamp) {
        long timestamp0;
        do {
            timestamp0 = timeGen();
        } while (timestamp0 <= lastTimestamp);
        return timestamp0;
    }

    /**
     * 返回以毫秒为单位的当前时间
     *
     * @return 当前时间(毫秒)
     */
    protected long timeGen() {
        return System.currentTimeMillis();
    }

    /**
     * 尝试解决时钟回拨<br>【* 仅用于 单机生成不对外 的情况 *】
     *
     * @param timestamp 当前时间戳
     * @return void
     */
    private void nonSharedClockBackwards(long timestamp) {
        if (this.dataCenterIdFlags >= UINT_MAX_VALUE && this.workerIdFlags >= UINT_MAX_VALUE) {
            throw new RuntimeException(MessageFormat.format("Clock moved backwards. Refusing to generate id for {0} milliseconds", lastTimestamp - timestamp));
        } else {
            //如果仅用于生成不重复的数值，尝试变更 dataCenterId 或 workerId 修复时钟回拨问题

            log.warn("Clock moved backwards. Refusing to generate id for {} milliseconds", lastTimestamp - timestamp);
            //先尝试变更 dataCenterId，当 dataCenterId 轮询一遍之后，尝试变更 workerId 并重置 dataCenterId
            if (this.dataCenterIdFlags >= UINT_MAX_VALUE) {
                if (++this.workerId > MAX_WORKER_ID) {
                    this.workerId = 0L;
                }
                this.workerIdFlags = setSpecifiedBitTo1(this.workerIdFlags, this.workerId);
                // 重置 dataCenterId 和 dataCenterIdFlags
                this.dataCenterIdFlags = this.dataCenterId = 0L;
            } else {
                if (++this.dataCenterId > MAX_DATA_CENTER_ID) {
                    this.dataCenterId = 0L;
                }
            }
            this.dataCenterIdFlags = setSpecifiedBitTo1(this.dataCenterIdFlags, this.dataCenterId);
            this.lastTimestamp = -1L;
            log.warn("Try to fix the clock moved backwards. timestamp : {}, worker Id : {}, datacenter Id : {}", timestamp, workerId, dataCenterId);
        }
    }

    /**
     * 尝试解决时钟回拨<br>【* 仅用于每毫秒生成量 不大于 1024 的情况 *】
     *
     * @param timestamp 当前时间戳
     * @return void
     */
    private void rate1024ClockBackwards(long timestamp) {
        if (this.basicSequence > (SEQUENCE_MASK - STEP_SIZE)) {
            throw new RuntimeException(MessageFormat.format("Clock moved backwards. Refusing to generate id for {0} milliseconds", lastTimestamp - timestamp));
        } else {
            log.warn("Clock moved backwards. Refusing to generate id for {} milliseconds", lastTimestamp - timestamp);
            this.basicSequence += STEP_SIZE;
            this.lastTimestamp = -1L;
            log.warn("Try to fix the clock moved backwards. timestamp : {}, basicSequence : {}", timestamp, basicSequence);
        }
    }

    /**
     * Set the specified bit to 1
     *
     * @param value raw long value
     * @param index bit index (From 0~31)
     * @return long value
     */
    private long setSpecifiedBitTo1(long value, long index) {
        return value |= (1L << index);
    }

    /**
     * Set the specified bit to 0
     *
     * @param value raw long value
     * @param index bit index (From 0~31)
     * @return long value
     */
    private long setSpecifiedBitTo0(long value, long index) {
        return value &= ~(1L << index);
    }

    /**
     * Get the specified bit
     *
     * @param value raw long value
     * @param index bit index(From 0-31)
     * @return 0 or 1
     */
    private int getSpecifiedBit(long value, long index) {
        return (value & (1L << index)) == 0 ? 0 : 1;
    }

}

3.3、缓存模型类

缓存操作不是本文的重点，用模型类代替；实际部署时可换作redis

package com.tuwer.cache;

import java.util.Set;
import java.util.concurrent.ConcurrentNavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;

/**
 * 模拟缓存
 *
 * @author 土味儿
 * Date 2023/1/3
 * @version 1.0
 */
public class CacheModel {
    /**
     * 并发Map
     */
    private static ConcurrentSkipListMap<Long, String> cache = new ConcurrentSkipListMap<>();

    /**
     * 存入缓存
     *
     * @param key
     * @param value
     */
    public static void put(Long key, String value) {
        cache.put(key, value);
        System.out.println("存入缓存；【key】" + key + "【value】" + value);
        print();
    }

    /**
     * 获取value
     *
     * @param key
     * @return
     */
    public static String get(Long key) {
        String v = cache.get(key);
        System.out.println("从缓存中获取；【key】" + key + "【value】" + v);
        return v;
    }

    /**
     * 删除key
     *
     * @param key
     */
    public static void del(Long key) {
        String v = cache.remove(key);
        System.out.println("从缓存中删除；【key】" + key + "【value】" + v);
        print();
    }

    /**
     * 删除小于等于key的多个值
     *
     * @param key
     */
    public static void delMany1(Long key) {
        Set<Long> keys = cache.keySet();
        int n = 0;
        for (Long k : keys) {
            if (k <= key) {
                cache.remove(k);
                n++;
            }
        }
        System.out.println("从缓存中删除小于等于；【" + key + "】的多个值；共有 " + n + " 个");
        print();
    }

    /**
     * 删除小于等于key的多个值
     * ConcurrentNavigableMap
     * @param key
     */
    public static void delMany(Long key) {
        // 得到批量确认信息Map（只能得到小于key的值）
        ConcurrentNavigableMap<Long, String> confirmMap = cache.headMap(key);
        System.out.println("从缓存中删除小于等于；【" + key + "】的多个值；共有 " + (confirmMap.size() + 1) + " 个");
        // 清空已经确认的
        confirmMap.clear();

        // 单独再删除等于key的值
        cache.remove(key);

        print();
    }

    public static void print() {
        System.out.println("当前缓存大小：" + cache.size());
        Set<Long> keys = cache.keySet();
        for (Long key : keys) {
            System.out.print(key);
            System.out.print(" | ");
            //System.out.println(cache.get(key));
        }
        System.out.println();
    }
}

4、配置类 MqConfig.java

package com.tuwer.config;

import com.tuwer.constant.Constants;
import org.springframework.amqp.core.*;
import org.springframework.amqp.rabbit.connection.CachingConnectionFactory;
import org.springframework.amqp.rabbit.core.RabbitAdmin;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.annotation.PostConstruct;
import javax.annotation.Resource;

/**
 * <p>配置类</p>
 *
 * @author 土味儿
 * Date 2023/1/5
 * @version 1.0
 */
@Configuration
public class MqConfig {
    @Resource
    private CachingConnectionFactory connectionFactory;
    @Resource
    private RabbitTemplate rabbitTemplate;

    @PostConstruct
    public void init(){        
        System.out.println("初始化...");
        // 删除普通空队列（排除掉备份队列），减轻RabbitMQ的压力
   }

    /**
     * 获取普通交换机
     *
     * @return
     */
    @Bean("normalExchange")
    public DirectExchange getNormalExchange() {
        return ExchangeBuilder
                .directExchange(Constants.NORMAL_EXCHANGE)
                // 持久化
                .durable(true)
                // 备份(候补)交换机
                .withArgument("alternate-exchange", Constants.BACKUP_EXCHANGE)
                .build();
    }

    /**
     * 备份交换机
     * 类型：fanout
     *
     * @return
     */
    @Bean("backupExchange")
    public FanoutExchange getBackupExchange() {
        return new FanoutExchange(Constants.BACKUP_EXCHANGE);
    }

    /**
     * 获取备份队列
     *
     * @return
     */
    @Bean("backupQueue")
    public Queue getBackupQueue() {
        return QueueBuilder.durable(Constants.BACKUP_QUEUE).build();
    }

    /**
     * 备份队列 绑定 备份交换机
     *
     * @param queue
     * @param exchange
     * @return
     */
    @Bean
    public Binding backupQueueBindBackupExchange(
            @Qualifier("backupQueue") Queue queue,
            @Qualifier("backupExchange") FanoutExchange exchange
    ) {
        return BindingBuilder.bind(queue).to(exchange);
    }

    /**
     * 用于动态创建队列、交换机，并绑定
     * @return
     */
    @Bean
    public RabbitAdmin rabbitAdmin(){
        //return new RabbitAdmin(connectionFactory);
        return new RabbitAdmin(rabbitTemplate);
    }

    /**
     * 用于设置动态监听
     * @return
     */
    @Bean
    public SimpleMessageListenerContainer simpleMessageListenerContainer(){
        SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);

        container.setConcurrentConsumers(10);
        container.setMaxConcurrentConsumers(50);
        // 手动确认
        container.setAcknowledgeMode(AcknowledgeMode.MANUAL);
        // 预取值
        container.setPrefetchCount(Constants.PRE_FETCH_SIZE);

        // 创建队列（在用户登录后创建）
        //createNormalQueueAndBind.create(username);
        //listenerContainer.setQueueNames("q_" + username);
        //listenerContainer.setMessageListener(myAckReceiver);

        return container;
    }
}

5、普通队列动态创建类

package com.tuwer.service;

import com.tuwer.constant.Constants;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.*;
import org.springframework.amqp.rabbit.core.RabbitAdmin;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.util.Locale;
import java.util.Objects;
import java.util.Properties;

/**
 * <p>动态创建队列</p>
 *
 * @author 土味儿
 * Date 2023/1/7
 * @version 1.0
 */
@Component
@Slf4j
public class CreateNormalQueueAndBind {
    @Resource
    private DirectExchange normalExchange;
    @Resource
    private RabbitAdmin rabbitAdmin;

    /**
     * 动态创建普通队列，并绑定至普通交换机
     *
     * @param routingKey
     */
    public void create(String routingKey) {
        String key = routingKey.toLowerCase(Locale.ROOT);
        String queueName = "q_" + key;

        // 创建普通队列
        Queue queue = null;

        // 查询队列属性，为null时，表示队列不存在
        Properties queueProperties = rabbitAdmin.getQueueProperties(queueName);

        // 队列不存在时，创建
        if (Objects.isNull(queueProperties)) {
            log.info("队列【{}】不存在，创建中...", queueName);
            queue = QueueBuilder.durable(queueName).maxLength(Constants.QUEUE_CAPACITY).build();
            rabbitAdmin.declareQueue(queue);
        }
        // 绑定至普通交换机
        if (Objects.nonNull(queue)) {
            Binding binding = BindingBuilder.bind(queue).to(normalExchange).with(key);
            rabbitAdmin.declareBinding(binding);
        }
    }
}

经过测试，如果队列满了的时候，再向队列发送消息时，最老的消息被丢弃，且不会启用备份交换机；为了防止信息丢失，加入死信交换机和死信队列，当前队列满了的时候，最老的信息进入死信交换机，再转至死信队列

• 原代码

// 原
queue = QueueBuilder.durable(queueName)
      .maxLength(Constants.QUEUE_CAPACITY)
      .build();

• 新代码

// 新
queue = QueueBuilder.durable(queueName)
      // 设置队列长度
      .maxLength(Constants.QUEUE_CAPACITY)
      // 设置死信交换机
      .deadLetterExchange(Constants.BACKUP_EXCHANGE)
      // 设置死信RoutingKey（死信队列）
      .deadLetterRoutingKey(Constants.BACKUP_QUEUE)
      // 改变溢出规则：当队列溢出时，拒绝接收新消息
      //.overflow(QueueBuilder.Overflow.rejectPublish)
      .build();

6、发布确认回调类

package com.tuwer.service;

import com.tuwer.cache.CacheModel;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import javax.annotation.Resource;

/**
 * <p>发布确认回调类</p>
 *
 * @author 土味儿
 * Date 2023/1/5
 * @version 1.0
 */
@Slf4j
@Component
public class MyConfirmCallback implements RabbitTemplate.ConfirmCallback {
    @Resource
    private RabbitTemplate rabbitTemplate;

    /**
     * 把当前类注入到 RabbitTemplate
     *
     * @PostConstruct 表示在执行当前类的构造时运行
     * 因为 ConfirmCallback接口是 RabbitTemplate的内部类
     */
    @PostConstruct
    public void init() {
        rabbitTemplate.setConfirmCallback(this);
    }

    /**
     * 交换机确认回调方法
     *
     * @param correlationData 回调消息
     * @param ack             交换机是否确认收到了消息：true:收到了；false:没有收到
     * @param cause           没有收到消息的原因
     */
    @Override
    public void confirm(CorrelationData correlationData, boolean ack, String cause) {
        // 消息ID
        String id = correlationData != null ? correlationData.getId() : "";
        if (ack) {
            // 收到
            log.info("交换机收到了消息！编号：{}", id);
            // 从缓存中删除
            CacheModel.del(Long.parseLong(id));
        } else {
            // 未收到
            log.info("交换机没有收到编号为：{} 的消息！原因：{}", id, cause);
        }
    }
}

7、生产者服务类

package com.tuwer.service;


import com.tuwer.cache.CacheModel;
import com.tuwer.constant.Constants;
import com.tuwer.util.SnowflakeUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.stereotype.Component;
import javax.annotation.Resource;
import java.util.*;

/**
 * <p>生产者</p>
 *
 * @author 土味儿
 * Date 2023/1/4
 * @version 1.0
 */
@Component
@Slf4j
public class Producer {
    @Resource
    private RabbitTemplate rabbitTemplate;
    @Resource
    private CreateNormalQueueAndBind createNormalQueueAndBind;

    /**
     * 发送消息
     *
     * @param msg
     */
    public void sendMsg(String msg, String routingKey) {
        String key = routingKey.toLowerCase(Locale.ROOT);
        // 创建普通队列，并绑定至普通交换机
        createNormalQueueAndBind.create(key);

        long id = SnowflakeUtil.getInstance().nextId();
        CorrelationData correlationData = new CorrelationData(String.valueOf(id));
        rabbitTemplate.convertAndSend(
                Constants.NORMAL_EXCHANGE,
                key,
                msg,
                correlationData);

        // 存入缓存
        CacheModel.put(id, msg);

        log.info("消息：【{}】已发送！编号：{}", msg, correlationData.getId());
    }
}

8、消费者服务类

8.1、备份队列消费者

备份队列固定不变；config中配置，系统启动后自动创建

package com.tuwer.service;

import com.tuwer.config.MqConfig;
import com.tuwer.constant.Constants;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.stereotype.Component;

/**
 * <p>备份消费者</p>
 *
 * @author 土味儿
 * Date 2023/1/5
 * @version 1.0
 */
@Slf4j
@Component
public class BackupConsumer {
    /**
     * 监听备份队列消息
     * @param message
     */
    @RabbitListener(queues = Constants.BACKUP_QUEUE)
    public void receiveMsg(Message message){
        String msg = new String(message.getBody());
        log.info("接收到备份队列的消息：【{}】", msg);
    }
}

8.2、普通队列消费者

• 队列不确定；用户登录后，动态切换要监控的队列；

• 如果用户退出后，也要更新监控列表；省略

package com.tuwer.service;

import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;


/**
 * <p>普通消费者</p>
 *
 * @author 土味儿
 * Date 2023/1/5
 * @version 1.0
 */
@Slf4j
@Component
public class NormalConsumer {
    @Resource
    private SimpleMessageListenerContainer listenerContainer;
    @Resource
    private MyAckReceiver myAckReceiver;
    @Resource
    private CreateNormalQueueAndBind createNormalQueueAndBind;

    /**
     * 监听普通队列消息
     * 动态切换要监控的队列   
     *   
     * @param username
     */
    //@RabbitListener(queues = "队列名称")
    public void receiveMsg(String username) {
        // 创建队列
        createNormalQueueAndBind.create(username);
        // 设置要监听的队列（用set，不是add）
        listenerContainer.setQueueNames("q_" + username);
        // 设置消息接收器
        listenerContainer.setMessageListener(myAckReceiver);

        // 当前监听的队列列表
        String[] queueNames = listenerContainer.getQueueNames();
        System.out.println("当前监听的队列：");
        for (String queueName : queueNames) {
            System.out.println(queueName);
        }
        System.out.println("----------");
    }
}

• 消息接收器

package com.tuwer.service;

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;

/**
 * <p>消息接收器</p>
 *
 * @author 土味儿
 * Date 2023/1/7
 * @version 1.0
 */
@Slf4j
@Component
public class MyAckReceiver implements ChannelAwareMessageListener {
    @Override
    public void onMessage(Message message, Channel channel) throws Exception {
        long deliveryTag = message.getMessageProperties().getDeliveryTag();
        try {
            String consumerQueue = message.getMessageProperties().getConsumerQueue();
            String msg = new String(message.getBody());
            log.info("MyAckReceiver的【{}】队列，收到的消息：【{}】", consumerQueue, msg);
            channel.basicAck(deliveryTag, true);
        } catch (Exception e) {
            channel.basicReject(deliveryTag, false);
            e.printStackTrace();
        }
    }
}

9、Controller接口类

9.1、发送消息

http://localhost:8080/sendMsg/用户名/消息

package com.tuwer.controller;

import com.tuwer.service.Producer;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

/**
 * <p>发送消息</p>
 *
 * @author 土味儿
 * Date 2023/1/5
 * @version 1.0
 */
@Slf4j
@RestController
public class ProducerController {
    @Resource
    private Producer producer;

    /**
     * 发送消息
     *
     * @param msg      消息内容
     * @param username 接收消息的用户
     * @return
     */
    @GetMapping("/sendMsg/{username}/{msg}")
    public String sendMsg(
            @PathVariable("msg") String msg,
            @PathVariable("username") String username
    ) {
        producer.sendMsg(msg, username);

        return "OK!";
    }
}

9.2、模拟用户登录

[http://localhost:8080/login/用户名

package com.tuwer.controller;

import com.tuwer.service.NormalConsumer;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

/**
 * <p>模拟登录</p>
 *
 * @author 土味儿
 * Date 2023/1/7
 * @version 1.0
 */
@Slf4j
@RestController
@RequestMapping("/login")
public class LoginController {
    @Resource
    private NormalConsumer consumer;

    /**
     * 登录
     *
     * @param username
     * @return
     */
    @GetMapping("/{username}")
    public String login(
            @PathVariable("username") String username
    ) {
        log.info("用户 {} 已登录", username);

        // 接收该用户的队列消息
        consumer.receiveMsg(username);

        return username;
    }
}

10、定时重发

缓存中未得到确认的消息，由定时器重新发送；省略…

11、项目结构图

六、测试

1、启动后自动创建交换机、队列

• 启动前

• 启动后

2、向用户user1发送消息

http://localhost:8080/sendMsg/user1/测试1

3、登录user1接收消息

http://localhost:8080/login/user1

4、向user2、user3分别发消息

当前登录用户是user1，向用户user2、user3发送消息时，user1是接收不到的，消息会存储在相应对列中

5、切换用户user3

由user1切换到user3，同时监控的队列由q_user1动态切换到q_user3，队列q_user3中的消息将被消费掉

6、再次向user1发消息

当前登录用户是user3，这时再向上一个登录用户user1发消息，消息应该不会被消费，存在q_user1队列中

7、备份交换机接收消息

• 本案例中发送消息前，先动态创建队列，一般不会出现信息无法路由的情况，也就不会因为无法路由而启动备份交换机（除非一些极端的情况）

• 当普通队列满的时候，再向其发送消息，最老的信息变为死信，进入死信交换机；本案例中把备份交换机当成死信交换机，备份队列当成死信队列。

• 向user2连发10条信息，且user2不登录，队列q_user2容量为5，溢出后最老的信息进入备份交换机

• 启动测试

• 改变溢出规则；默认是丢弃最老(开头)的消息

在创建队列时加上overflow(QueueBuilder.Overflow.rejectPublish)，改为拒绝接收新消息，此时生产者会收到拒绝接收的消息提示，缓存中的消息将不会被删除，而是定时重发；备份交换机也不会启用，拒绝的信息不会进入备份队列，不符合设计要求，所以使用默认的溢出规则。

七、不足

• 每个用户对应一个普通队列；当用户过多时，相应的队列也会很多，并且队列是持久化的，会占用较多的系统资源；解决思路：定时删除空队列

• …