CODEWITHSUNDEEP
springspring-integrationmqttpaho
sura2k
sura2k

Reputation: 7517

Spring Mqtt - Publish messages to multiple topics programmatically

How can I publish messages with different topics programmatically?

<mqtt:outbound-channel-adapter id="mqttOut" 
    auto-startup="true" 
    client-id="foo"
    url="tcp://localhost:1883"
    client-factory="clientFactory"
    default-qos="0"
    default-retained="false"
    default-topic="bar"
    async="true"
    async-events="true" />

I tried Spring integration MQTT publish & subscribe to multiple topics, but were not able to configure.

Also tried with MqttPahoMessageHandlerAdapter which has a publish() but protected.

Going with org.eclipse.paho.client.mqttv3.MqttAsyncClient and org.eclipse.paho.client.mqttv3.MqttCallback is very easy. But I would like to stick with spring all the way.

Appreciate if somebody can points me to a correct direction.

Upvotes: 2

Views: 3184

Answers (2)

Artem Bilan
Artem Bilan

Reputation: 121177

You can do that with Spring Integration anyway! Having a lot of EIP components implementation and Spring power on board (injection, SpEL etc,), plus switching on a bit of imagination, we can reach any end-application requirements even without any Java code.

So, <mqtt:outbound-channel-adapter> allows determine topic at runtime. Instead of default-topic you should supply MqttHeaders.TOPIC MessageHeader.

So, if you have a requirement to send the same message to several topics, you just build a copy of that message for each topic. The <splitter> can help us:

<int:splitter input-channel="enricheMessage" output-channel="sendMessage" apply-sequence="false">
    <int-groovy:script>
        ['topic1', 'topic2', 'topic3'].collect {
            org.springframework.integration.support.MessageBuilder.withPayload(payload)
                    .copyHeaders(headers)
                    .setHeader(org.springframework.integration.mqtt.support.MqttHeaders.TOPIC, it)
                    .build()
        }
    </int-groovy:script>
</int:splitter>

sendMessage can be ExecutorChannel to achieve the parallel publishing.

UPDATE

You can achieve the same iteration and message enrichment logic with similar Java code using ref and method on <splitter>. Of course, we can do that even with SpEL , but it will look a bit complex with Collection Projection.

Upvotes: 2

Gary Russell
Gary Russell

Reputation: 174494

Declare a <publish-subscribe-channel id="toMqtt" />; set it as the channel attribute on each outbound channel adapter; the message will be sent to each adapter.

Upvotes: 2

Related Questions