[CAMEL-5670] camel-mqtt - Nullpointer Exception when disconnected from broker

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.10.1
• Fix Version/s: 2.10.2, 2.11.0
• Component/s: camel-mqtt
• Estimated Complexity: Unknown
• Assignee: Claus Ibsen
• Reporter: Stefan Hudelmaier
• Created: 01/Oct/12 08:44
• Updated: 06/Oct/12 15:12
• Resolved: 06/Oct/12 15:12

Description

Hi,

from time to time, we get the following exception when producing messages via camel-mqtt:

Caused by: java.lang.NullPointerException
	at org.fusesource.mqtt.client.CallbackConnection.publish(CallbackConnection.java:551)
	at org.fusesource.mqtt.client.CallbackConnection.publish(CallbackConnection.java:545)
	at org.apache.camel.component.mqtt.MQTTEndpoint.publish(MQTTEndpoint.java:166)
	at org.apache.camel.component.mqtt.MQTTProducer.doProcess(MQTTProducer.java:66)
	at org.apache.camel.component.mqtt.MQTTProducer.process(MQTTProducer.java:38)
	at org.apache.camel.util.AsyncProcessorHelper.process(AsyncProcessorHelper.java:73)
[...]

From looking at the source of both camel-mqtt and the fusesource mqtt client, it looks like that this is caused by the mqtt-client being disconnected and trying to invoke the onFailure method on the callback:

CallbackConnection.java

public void publish(UTF8Buffer topic, Buffer payload, QoS qos, boolean retain, Callback<Void> cb) {
        queue.assertExecuting();
        if( disconnected ) {
            cb.onFailure(createDisconnectedError());
            return;
        }
        PUBLISH command = new PUBLISH().qos(qos).retain(retain);
        command.topicName(topic).payload(payload);
        send(command, cb);
    }

camel-mqtt passes in null for the callback though. Wouldn't it be better if a more fitting exception were thrown, or if camel passed in a Callback in order to receive the onFailure event when disconnected from the broker?