Perform Action in MQTT Subscriber - mqtt

Question

This mqtt subscriber code works fine. I can easily subscribe to messages which are published at broker.hivemq.com with respective topic.
public class AccelerometerSubscriber implements MqttCallback,
IMqttActionListener {
public static void main(String[] args) throws MqttException {
int QUALITY_OF_SERVICE = 2;
MqttClient client=new MqttClient("tcp://broker.hivemq.com:1883",
MqttClient.generateClientId());
client.setCallback( new SimpleMqttCallBack() );
client.connect();
System.out.println("Subscribing ....");
client.subscribe("MQTT Examples"); }
System.out.println("some action"); //------------right here--------------
public void connectionLost(Throwable throwable) {
System.out.println("Connection to MQTT broker lost!"); }
public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
System.out.println("Message received:\n\t"+ new String(mqttMessage.getPayload()) );
}
public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
// not used in this example
}}
Now I want to perform action only when a message is received. I'm unable to do that.

Answer 1

You have a class (AccelerometerSubscriber) that implements the interface MqttCallback, use an instance of it instead of doing client.setCallback( new SimpleMqttCallBack() );
public class AccelerometerSubscriber implements MqttCallback, IMqttActionListener {
public static void main(String[] args) throws MqttException {
AccelerometerSubscriber as = new AccelerometerSubscriber();
int QUALITY_OF_SERVICE = 2;
MqttClient client = new MqttClient("tcp://broker.hivemq.com:1883", MqttClient.generateClientId());
client.setCallback(as);
client.connect();
System.out.println("Subscribing ....");
client.subscribe("MQTT Examples");
}
#Override
public void connectionLost(Throwable throwable) {
System.out.println("Connection to MQTT broker lost!");
}
#Override
public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
//message is received is here!!!
System.out.println("Message received:\n\t" + new String(mqttMessage.getPayload()));
}
#Override
public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
System.out.println("deliveryComplete");
}
#Override
public void onFailure(IMqttToken arg0, Throwable arg1) {
System.out.println("onFailure");
}
#Override
public void onSuccess(IMqttToken arg0) {
System.out.println("onSuccess");
}
}