第八章 RabbitMQ之消息转换器

一、介绍

二、案例演示

[2.1. 创建SpringBoot工程](#2.1. 创建SpringBoot工程)

[2.2. 父工程pom依赖](#2.2. 父工程pom依赖)

[2.3. 生产者pom依赖](#2.3. 生产者pom依赖)

[2.4. 生产者配置文件](#2.4. 生产者配置文件)

[2.5. 生产者代码](#2.5. 生产者代码)

[2.6. 消费者RabbitMQConfig](#2.6. 消费者RabbitMQConfig)

[2.7. 消费者pom依赖](#2.7. 消费者pom依赖)

[2.8. 消费者配置文件](#2.8. 消费者配置文件)

[2.9. 消费者核心代码](#2.9. 消费者核心代码)

[2.10. 运行效果](#2.10. 运行效果)

[2.11. 取消自定义转换器效果](#2.11. 取消自定义转换器效果)

一、介绍

在RabbitMQ中，消息转换器（Message Converter）用于在发送消息时将Java对象转换为RabbitMQ可以理解的字节流，以及在消费者接收消息时将字节流转换回Java对象。

在实际的RabbitMQ应用中，你会配置转换器作为Spring AMQP的一部分，并在发送和接收消息时由Spring框架自动应用转换。如果需要特定的序列化行为，你可以实现自定义的转换器。

Spring对消息对象的处理是由org.springframework.amqp.support.converter.MessageConverter来处理的，而默认实现是SimpleMessageConverter。

基于JDK的ObjectOutputStream完成序列化存在下列问题：

1. JDK的序列化有安全风险

2. JDK序列化的消息太大

3. JDK序列化的消息可读性差

建议采用JSON序列化代替默认的JDK序列化，要做两件事情：

在publisher和consumer中都要引入jackson依赖：

在publisher和consumer中都要配置MessageConverter：

我们这边作为演示就直接配在启动类里，实际项目中可以单独定义转换器类

二、案例演示

案例需求：

测试利用SpringAMQP发送对象类型的消息声明一个队列，名为object.queue

编写单元测试，向队列中直接发送一条消息，消息类型为Map

在控制台查看消息，总结你能发现的问题

2.1. 创建SpringBoot工程

完整的工程目录结构及代码文件如下：

2.2. 父工程pom依赖

引入核心依赖

XML 复制代码

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.3.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>mq-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>mq-demo</name>
    <description>mq-demo</description>
    <url/>
    <licenses>
        <license/>
    </licenses>
    <developers>
        <developer/>
    </developers>
    <scm>
        <connection/>
        <developerConnection/>
        <tag/>
        <url/>
    </scm>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-amqp</artifactId>
        </dependency>

        <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>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.14.3</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2.3. 生产者pom依赖

XML 复制代码

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.3.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>publisher</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>publisher</name>
    <description>publisher</description>
    <url/>
    <licenses>
        <license/>
    </licenses>
    <developers>
        <developer/>
    </developers>
    <scm>
        <connection/>
        <developerConnection/>
        <tag/>
        <url/>
    </scm>
    <properties>
        <java.version>17</java.version>
    </properties>
    <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>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2.4. 生产者配置文件

XML 复制代码

spring:
  rabbitmq:
    # 主机
    host: 127.0.0.1
    # 端口
    port: 5672
    # 默认用户密码是guest guest 如果需要自己创建新用户，参看我的第四章节内容
    username: Wangzhexiao
    password: Wangzhexiao
    # 默认的虚拟主机是/ 如果需要自己创建虚拟主机，参看我的第四章节内容
    virtual-host: /hangzhou

2.5. 生产者代码

SpringAMQP提供了RabbitTemplate工具类，方便我们发送消息。发送消息代码如下：

java 复制代码

package com.example.publisher;

import jakarta.annotation.Resource;
import org.junit.jupiter.api.Test;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.HashMap;
import java.util.Map;

@SpringBootTest
class PublisherApplicationTests {

    @Resource
    private RabbitTemplate rabbitTemplate;

    @Test
    void sendMessage() throws InterruptedException {
        String exchangeName = "wzx.topic";
        Map<String,Object> msg = new HashMap<>(2);
        msg.put("name", "wangzhexiao");
        msg.put("motto", "只要学不死，就往死里学！");
        rabbitTemplate.convertAndSend(exchangeName,"china.news", msg);
    }
}

java 复制代码

package com.example.publisher;

import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter;
import org.springframework.amqp.support.converter.MessageConverter;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class PublisherApplication {

    public static void main(String[] args) {
        SpringApplication.run(PublisherApplication.class, args);
    }

    @Bean
    public MessageConverter messageConverter(){
        return new Jackson2JsonMessageConverter();
    }
}

2.6. 消费者RabbitMQConfig

java 复制代码

package com.example.consumer;

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

@Configuration
public class RabbitMQConfig {

    @Bean
    Queue topicQueue1() {
        // 使用 QueueBuilder 创建一个持久化队列
        return QueueBuilder.durable("topic.queue1").build();
    }

    @Bean
    Queue topicQueue2() {
        // 使用 QueueBuilder 创建一个持久化队列
        return QueueBuilder.durable("topic.queue2").build();
    }

    @Bean
    TopicExchange topicExchange() {
        return new TopicExchange("wzx.topic");
    }

    @Bean
    Binding binding1(Queue topicQueue1, TopicExchange topicExchange) {
        return BindingBuilder.bind(topicQueue1).to(topicExchange).with("china.#"); // 绑定队列和交换机
    }

    @Bean
    Binding binding2(Queue topicQueue2, TopicExchange topicExchange) {
        return BindingBuilder.bind(topicQueue2).to(topicExchange).with("#.news"); // 绑定队列和交换机
    }
}

2.7. 消费者pom依赖

XML 复制代码

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.3.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>consumer</name>
    <description>consumer</description>
    <url/>
    <licenses>
        <license/>
    </licenses>
    <developers>
        <developer/>
    </developers>
    <scm>
        <connection/>
        <developerConnection/>
        <tag/>
        <url/>
    </scm>
    <properties>
        <java.version>17</java.version>
    </properties>
    <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>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.34</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2.8. 消费者配置文件

XML 复制代码

spring:
  rabbitmq:
    # 主机
    host: 127.0.0.1
    # 端口
    port: 5672
    # 默认用户密码是guest guest 如果需要自己创建新用户，参看我的第四章节内容
    username: Wangzhexiao
    password: Wangzhexiao
    # 默认的虚拟主机是/ 如果需要自己创建虚拟主机，参看我的第四章节内容
    virtual-host: /hangzhou

2.9. 消费者核心代码

SpringAMQP提供声明式的消息监听，我们只需要通过注解在方法上声明要监听的队列名称，将来SpringAMQP就会把消息传递给当前方法：

java 复制代码

package com.example.consumer;

import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.ExchangeTypes;
import org.springframework.amqp.rabbit.annotation.Exchange;
import org.springframework.amqp.rabbit.annotation.Queue;
import org.springframework.amqp.rabbit.annotation.QueueBinding;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.stereotype.Component;

import java.util.Map;

@Slf4j
@Component
public class SimpleListener {

    @RabbitListener(queues = "topic.queue1")
    public void listener1(Map<String, Object> msg) throws InterruptedException {
        System.out.println("消费者1：人生是个不断攀登的过程【" + msg + "】");
    }

    @RabbitListener(queues = "topic.queue2")
    public void listener2(Map<String, Object> msg) throws InterruptedException {
        System.err.println("消费者2：人生是个不断攀登的过程【" + msg + "】");
    }
}

2.10. 运行效果

通过自定义的消息转换器，我们可以看到在RabbitMQ浏览器界面中消息内容为正常的中文：

2.11. 取消自定义转换器效果

java 复制代码

package com.example.consumer;

import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter;
import org.springframework.amqp.support.converter.MessageConverter;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class ConsumerApplication {

    public static void main(String[] args) {
        SpringApplication.run(ConsumerApplication.class, args);
    }

}

我们删除生产者启动类中声明的转换器代码，然后单独启动生产者并进入RabbitMQ浏览器界面，查看队列中的消息，可以看到消息内容为一串序列化后的乱码：