Paho MQTT Exception in Thread

Question

So, I downloaded a Java code to demonstrate Paho MQTT.

 public class Thermometer {

    public static final String BROKER_URL = "tcp://test.mosquitto.org:1883";

    public static final String TOPIC = "xyz.abc";

    private MqttClient client;


    public Thermometer() {
        try {
            MemoryPersistence per = new MemoryPersistence();
            String clientId = UUID.randomUUID().toString();
            client = new MqttClient(BROKER_URL, clientId, per);
        } catch (MqttException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

But when I try to run it, it locates at client = new MqttClient(BROKER_URL, clientId, per);with

Exception in thread "main" java.lang.IllegalArgumentException at org.eclipse.paho.client.mqttv3.MqttClient.(MqttClient.java:170) at mqtt_pub.Thermometer.(Thermometer.java:26) at mqtt_pub.Thermometer.main(Thermometer.java:65)

Can anyone fix this?

Answer 1

So, I'd reckon you try to take a look at the source code of MttqClient, where, you shall see that the uuid can only have a length of up to 23 characters.

if (clientId == null || clientId.length() == 0 || clientId.length() > 23)  
{
      throw new IllegalArgumentException();
}

But here, the UUID.randomUUID().toString() returns a string with the length of 36 characters.