Spring Integration Dispatcher has no subscribers for channel

Question

I'm using spring integration and its support for MQTT; I saw the spring integration documentation and my simple test case is to publish a message on a MQTT topic. The Spring documentation is located here: http://docs.spring.io/spring-integration/reference/html/mqtt.html#_configuring_with_java_configuration_15

I'm using these versions:

spring 4.3.4
spring integration 4.3.5

I built this simple configuration class:

@Configuration
@IntegrationComponentScan
public class CommunicationServerApplication
{
    @Bean
    public MqttPahoClientFactory mqttClientFactory()
    {
        DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
        factory.setServerURIs(mqttServerUris);
        if (StringUtils.hasText(mqttUsername) && StringUtils.hasText(mqttPassword))
        {

            factory.setUserName(mqttUsername);
            factory.setPassword(mqttPassword);
        }
        factory.setConnectionTimeout(mqttConnectionTimeout);
        factory.setKeepAliveInterval(mqttKeepAliveInterval);
        factory.setPersistence(new MqttDefaultFilePersistence(mqttPersistenceFileDirectory));
        return factory;
    }

    @Bean
    @ServiceActivator(inputChannel = "mqttOutboundChannel", autoStartup="true")
    public MessageHandler mqttOutbound()
    {
        String clientId = mqttClientId;
        if( !StringUtils.hasText(clientId) )
        {
            clientId = UUID.randomUUID().toString();
        }
        MqttPahoMessageHandler messageHandler = new MqttPahoMessageHandler(clientId, mqttClientFactory());
        messageHandler.setAsync(true);
        messageHandler.setDefaultTopic(mqttTopic);
        if( mqttQos >= 0 && mqttQos <=2 )
        {

            messageHandler.setDefaultQos(mqttQos);
        }
        return messageHandler;
    }

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

    @MessagingGateway(defaultRequestChannel = "mqttOutboundChannel")
    public interface MqttMsgproducer
    {

        void sendToMqtt(String data);
    }
}

And then I used this simple test case:

@ContextConfiguration(value ={ "classpath:app-ctx.xml"})
@RunWith(SpringJUnit4ClassRunner.class)
public class SimpleMqttTestSuite
{
    private static final Logger logger = LoggerFactory.getLogger(SimpleMqttTestSuite.class.getName());
    @Autowired
    private MqttMsgproducer sender;
    @Test
    public void startServerTest()
    {
        try
        {
            sender.sendToMqtt("Hello");
        }
        catch (Exception e)
        {
            logger.error("Error", e);
        }
    }
}

My app-ctx.xml is:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:oxm="http://www.springframework.org/schema/oxm"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd  
    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd 
    http://www.springframework.org/schema/oxm http://www.springframework.org/schema/oxm/spring-oxm.xsd 
    http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <context:component-scan base-package="it.olegna.test.integration" />
    <context:property-placeholder location="classpath:configuration.properties"
        order="0" ignore-resource-not-found="true" ignore-unresolvable="true" />    
</beans>

Executing the simple test, I'm having this error:

2016-12-20 10:46:33,889 49967 [nioEventLoopGroup-3-1] ERROR - Errore 
org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel 'org.springframework.context.support.GenericApplicationContext@2e6a8155.mqttOutboundChannel'.; nested exception is org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers
    at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:81) ~[spring-integration-core-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423) ~[spring-integration-core-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:373) ~[spring-integration-core-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:115) ~[spring-messaging-4.3.4.RELEASE.jar:4.3.4.RELEASE]
    at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:45) ~[spring-messaging-4.3.4.RELEASE.jar:4.3.4.RELEASE]
    at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:105) ~[spring-messaging-4.3.4.RELEASE.jar:4.3.4.RELEASE]
    at org.springframework.messaging.core.AbstractMessageSendingTemplate.convertAndSend(AbstractMessageSendingTemplate.java:143) ~[spring-messaging-4.3.4.RELEASE.jar:4.3.4.RELEASE]
    at org.springframework.messaging.core.AbstractMessageSendingTemplate.convertAndSend(AbstractMessageSendingTemplate.java:135) ~[spring-messaging-4.3.4.RELEASE.jar:4.3.4.RELEASE]
    at org.springframework.integration.gateway.MessagingGatewaySupport.send(MessagingGatewaySupport.java:375) ~[spring-integration-core-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.integration.gateway.GatewayProxyFactoryBean.invokeGatewayMethod(GatewayProxyFactoryBean.java:477) ~[spring-integration-core-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.integration.gateway.GatewayProxyFactoryBean.doInvoke(GatewayProxyFactoryBean.java:429) ~[spring-integration-core-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.integration.gateway.GatewayProxyFactoryBean.invoke(GatewayProxyFactoryBean.java:420) ~[spring-integration-core-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.integration.gateway.GatewayCompletableFutureProxyFactoryBean.invoke(GatewayCompletableFutureProxyFactoryBean.java:65) ~[spring-integration-core-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.4.RELEASE.jar:4.3.4.RELEASE]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213) ~[spring-aop-4.3.4.RELEASE.jar:4.3.4.RELEASE]

I can't figure what I'm missing in the configuration. Can anybody give to me a tip?

thank you

Angelo

Not an answer to your question, but probably useful for some who search for the error message in the title: I had a similar error when following the MQTT example from the Spring 5 documentation. I had to replace `adapter.setOutputChannel(mqttInputChannel())` with `adapter.setOutputChannelName("mqttInputChannel")` to make it work. — Henrik Solgaard, Apr 18 '18 at 21:42

Gary Russell · Answer 1 · 2016-12-20T21:02:25.853

11

Your solution is incorrect - you must not subscribe within a channel bean definition. I believe your problem is that you are missing @EnableIntegration on the class.

edited Dec 20 '16 at 21:02

answered Dec 20 '16 at 14:02

Gary Russell

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I was hoping in some clarification :) I tried as you suggested and it works – Angelo Immediata Dec 20 '16 at 15:22
@EnableIntegration fix has nothing to do with subscribing within a channel bean definition – Eduardo Mar 12 '20 at 13:57
What is the best approach to subscribe out side bean definition? – Tukaram Bhosale Mar 13 '20 at 11:24
It is unusual (rare) to **ever subscribe to a channel from user code**; normally, the framework will automatically subscribe consumers when they are started (usually automatically). – Gary Russell Mar 13 '20 at 13:35
1

@GaryRussell does the EnableIntegration Annotation need to go where my channels are defined? I'm still receiving the dispatcher error along with [link](https://stackoverflow.com/questions/64669208/spring-cloud-stream-dependency-issue) this error sometimes, it seems to me they are related. – Beez Nov 03 '20 at 21:41
If it's a spring-cloud-stream app, you don't need it at all, Spring Boot will automatically configure it; for a non-boot app, it needs to go on a `@Configuration` class. `Dispatcher has no subscribers` can happen in a number of circumstances/misconfiguration. It's best to ask a new question showing your code and configuration. The other error has nothing to do with Spring Integration, it looks like a class path incompatibility issue, just as Soby Chacko has commented. – Gary Russell Nov 03 '20 at 22:24
I got it working by simply adding `@EnableIntegration` to my handler that extends the AbstractReplyProducingMessageHandler without having to subscribe it using `directChannel.subscribe(handler);` – mariano Jul 01 '22 at 14:07

Angelo Immediata · Answer 2 · 2016-12-20T15:36:49.387

I solved my issue

It was related to the fact that I built the Channel but now handler have been subscribed

In my application class I did the following:

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

As you can see now I manually add subscribe the bean mqttOutbound (the message handler) to the Channel

By doing in this way all works

I hope this can help

Angelo

UPDATE AFTER Gary Russell ANSWER

As suggested by Gary Russell I didn't subscribe to the Channel

I added the annotation @EnableIntegration

So my Application class now is the following:

@Configuration
@IntegrationComponentScan
@EnableIntegration
public class CommunicationServerApplication
{
    @Bean
    public MqttPahoClientFactory mqttClientFactory()
    {
        DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
        factory.setServerURIs(mqttServerUris);
        if (StringUtils.hasText(mqttUsername) && StringUtils.hasText(mqttPassword))
        {

            factory.setUserName(mqttUsername);
            factory.setPassword(mqttPassword);
        }
        factory.setConnectionTimeout(mqttConnectionTimeout);
        factory.setKeepAliveInterval(mqttKeepAliveInterval);
        factory.setPersistence(new MqttDefaultFilePersistence(mqttPersistenceFileDirectory));
        return factory;
    }

    @Bean
    @ServiceActivator(inputChannel = "mqttOutboundChannel", autoStartup="true")
    public MessageHandler mqttOutbound()
    {
        String clientId = mqttClientId;
        if( !StringUtils.hasText(clientId) )
        {
            clientId = UUID.randomUUID().toString();
        }
        MqttPahoMessageHandler messageHandler = new MqttPahoMessageHandler(clientId, mqttClientFactory());
        messageHandler.setAsync(true);
        messageHandler.setDefaultTopic(mqttTopic);
        if( mqttQos >= 0 && mqttQos <=2 )
        {

            messageHandler.setDefaultQos(mqttQos);
        }
        return messageHandler;
    }

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

    @MessagingGateway(defaultRequestChannel = "mqttOutboundChannel")
    public interface MqttMsgproducer
    {

        void sendToMqtt(String data);
    }
}

Spring Integration Dispatcher has no subscribers for channel

2 Answers2

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