SpringBoot가 MQTT 메시지 전송 및 수신을 구현하는 방법

<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-integration -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-integration</artifactId>
    <version>2.5.1</version>
</dependency>
 
<!-- https://mvnrepository.com/artifact/org.springframework.integration/spring-integration-stream -->
<dependency>
    <groupId>org.springframework.integration</groupId>
    <artifactId>spring-integration-stream</artifactId>
    <version>5.5.5</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.integration/spring-integration-mqtt -->
<dependency>
    <groupId>org.springframework.integration</groupId>
    <artifactId>spring-integration-mqtt</artifactId>
    <version>5.5.5</version>
</dependency>

#mqtt配置
mqtt:
  username: 123
  password: 123
  #MQTT-服务器连接地址，如果有多个，用逗号隔开
  url: tcp://127.0.0.1:1883
  #MQTT-连接服务器默认客户端ID
  client:
    id: ${random.value}
  default:
    #MQTT-默认的消息推送主题，实际可在调用接口时指定
    topic: topic,mqtt/test/#
    #连接超时
  completionTimeout: 3000