[MQTT] Dispatcher has no subscribers for channel

转载自：​https://zhuanlan.zhihu.com/p/489740094

使用 spring-boot-starter-integration 方式实现的 mqtt，报错详情

logDispatcher has no subscribers for channel 'mqttOutboundChannel'.; nested exception is org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers, failedMessage=GenericMessage []

报错代码

/** 
 * @author aqin1012 AQin. 
 * @date 2022/2/23 9:16 AM 
 * @Version 1.0 
 */ 
@Configuration 
@IntegrationComponentScan 
public class MqttSenderConfig { 
    @Autowired 
    private MqttProperties prop; 

    @Autowired 
    MqttEncryptHelper mqttEncryptHelper; 

    @Bean 
    public MqttPahoClientFactory mqttClientFactory() {DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory(); 
        MqttConnectOptions mqttConnectOptions = new MqttConnectOptions(); 
        mqttConnectOptions.setServerURIs(new String[]{prop.getHostUrl()}); 
        mqttConnectOptions.setUserName(prop.getUsername()); 
        mqttConnectOptions.setPassword(prop.getPassword().toCharArray()); 
        // 客户端断线时暂时不清除，直到超时注销 
        mqttConnectOptions.setCleanSession(false); 
        mqttConnectOptions.setKeepAliveInterval(prop.getKeepAliveInterval()); 
        mqttConnectOptions.setAutomaticReconnect(true); 
        factory.setConnectionOptions(mqttConnectOptions); 
        return factory; 
 } 

    @Bean 
    @ServiceActivator(inputChannel = "mqttOutboundChannel") 
    public MessageHandler mqttOutbound() { 
        MqttPahoMessageHandler messageHandler = new MqttPahoMessageHandler(prop.getClientId() + "-pub-" + Instant.now().toEpochMilli(), mqttClientFactory()); 
        messageHandler.setAsync(true); 
        messageHandler.setDefaultQos(0); 
        messageHandler.setDefaultTopic(prop.getSenderDispatchTopic()); 
        return messageHandler; 
 } 

    @Bean 
    public MessageChannel mqttOutboundChannel() {return new DirectChannel(); 
  } 

} 

报错分析

由报错信息可以看出来是由于频道没有订阅者，由于我的 MARKDOWN_HASH17fdb716b8346c721481335713824d0aMARKDOWNHASH() 和 mqttOutbound()是绑定的，_于是我就试着把给频道手动添加订阅者：

mqttOutboundChannel_()_ 做如下修改：

@Bean 
public MessageChannel mqttOutboundChannel() {DirectChannel dc = new DirectChannel(); 
    dc.subscribe(mqttOutbound()); 
    return dc; 
} 

再次运行服务

搞定 ～ 撒花！！！

很多博文给出的解决方案是添加注解 @EnableIntegration 但是我这边并未起作用（有知道原因的大佬麻烦不吝指导 ～～ 谢谢呢 )