MQTTWrapper.java

package ch.epfl.gsn.networking.mqtt;

import java.io.Serializable;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttAsyncClient;
import org.eclipse.paho.client.mqttv3.MqttCallbackExtended;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import ch.epfl.gsn.beans.AddressBean;
import ch.epfl.gsn.beans.DataField;
import ch.epfl.gsn.beans.StreamElement;
import ch.epfl.gsn.wrappers.AbstractWrapper;

public class MQTTWrapper extends AbstractWrapper implements  MqttCallbackExtended{
	
	private final transient Logger logger = LoggerFactory.getLogger(MQTTWrapper.class);
	
	private MqttAsyncClient client;
	private AddressBean addressBean;
	private String serverURI;
	private String clientID;
	private String topic;
	private int qos;

	@Override
	public DataField[] getOutputFormat() {
		return new DataField[] {new DataField( "raw_packet" , "BINARY" , "The packet contains raw data received in the MQTT payload." ) };
	}

	@Override
	public boolean initialize() {
		try {
			addressBean = getActiveAddressBean( );
			serverURI = addressBean.getPredicateValue("uri");
			if ( serverURI == null || serverURI.trim().length() == 0 ) {
				logger.error( "The uri parameter is missing from the MQTT wrapper, initialization failed." );
				return false;
			}
			clientID = addressBean.getPredicateValue("client_id");
			if ( clientID == null || clientID.trim().length() == 0 ) {
				logger.error( "The client_id parameter is missing from the MQTT wrapper, initialization failed." );
				return false;
			}
			topic = addressBean.getPredicateValue("topic");
			if ( topic == null || topic.trim().length() == 0 ) {
				logger.error( "The topic parameter is missing from the MQTT wrapper, initialization failed." );
				return false;
			}
			qos = addressBean.getPredicateValueAsInt("qos", 0);
			if (qos < 0 || qos > 2) {
				logger.error( "The qos parameter from MQTT wrapper can be 0, 1 or 2 (found "+qos+"), initialization failed." );
				return false;
			}
			client = new MqttAsyncClient(serverURI, clientID);
			client.setCallback(this);
			client.connect();			
		}catch (Exception e){
			logger.error("Error in instanciating MQTT broker with "+topic+" @ "+serverURI,e);
			return false;
		}
		return true;
	}

	@Override
	public void dispose() {
		try {
			if (client.isConnected()){
				client.unsubscribe(topic);
				client.disconnect();
			}
			client.close();
		} catch (MqttException e) {
			logger.warn("Error while closing the MQTT client.", e);
		}
	}

	@Override
	public String getWrapperName() {
		return "MQTTWrapper["+topic+"]";
	}

	@Override
	public void connectionLost(Throwable e) {
		logger.warn("Connection to MQTT server lost. Reconnecting in 3s...", e);
		try {
			Thread.sleep(3000);
			client.reconnect();
		} catch (Exception e1) {
			logger.error("Error while reconnecting to server "+ serverURI, e1);
		}
	}

	@Override
	public void deliveryComplete(IMqttDeliveryToken token) {
		//MQTTWrapper doesn't publish		
	}

	@Override
	public void messageArrived(String s, MqttMessage m) throws Exception {
		logger.info("Message received on topic " + s + ": "+new String(m.getPayload()));
		StreamElement streamElement = new StreamElement(getOutputFormat(), new Serializable[] {m.getPayload()}, System.currentTimeMillis());
        postStreamElement(streamElement);
	}

	@Override
	public void connectComplete(boolean reconnect, String s) {
		if (!reconnect){
			try {
				client.subscribe(topic, qos);
			} catch (MqttException e) {
				logger.error("Error while subscribing to topic "+topic+" with qos "+qos, e);
			}
		}else{
			logger.debug("MQTT server reconnected "+s);
		}		
	}	
}