How to read x-death header of a RabbitMQ dead-lettered message using Spring Boot? - spring

Question

I am trying to implement re-routing of dead-lettered messages as described in this answer. I am using Spring config. I have no idea on how to read the headers to get the original routing key and original queue. The following is my config:
#Configuration
public class NotifEngineRabbitMQConfig {
#Bean
public MessageHandler handler(){
return new MessageHandler();
}
#Bean
public Jackson2JsonMessageConverter messageConverter(){
return new Jackson2JsonMessageConverter();
}
#Bean
public MessageListenerAdapter messageListenerAdapter(){
return new MessageListenerAdapter(handler(), messageConverter());
}
/**
* Listens for incoming messages
* Allows multiple queue to listen to
* */
#Bean
public SimpleMessageListenerContainer simpleMessageListenerContainer(){
SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
container.addQueueNames(QUEUE_TO_LISTEN_TO.split(","));
container.setMessageListener(messageListenerAdapter());
container.setConnectionFactory(rabbitConnectionFactory());
container.setDefaultRequeueRejected(false);
return container;
}
#Bean
public ConnectionFactory rabbitConnectionFactory(){
CachingConnectionFactory factory = new CachingConnectionFactory(HOST);
factory.setUsername(USERNAME);
factory.setPassword(PASSWORD);
return factory;
}
}

Answer 1

The headers are not available using "old" style Pojo messaging (with a MessageListenerAdapter). You need to implement MessageListener which gives you access to the headers.
However, you will need to invoke the converter yourself in that case and, if you are using request/reply messaging, you lose the reply mechanism within the adapter and you have to send the reply yourself.
Alternatively, you can use a custom message converter and "enhance" the converted object with the header after invoking the standard converter.
Consider instead using the newer style POJO messaging with #RabbitListener - it gives you access to the headers and has request/reply capability.
Here's an example:
#SpringBootApplication
public class So37581560Application {
public static void main(String[] args) {
SpringApplication.run(So37581560Application.class, args);
}
#Bean
public FooListener fooListener() {
return new FooListener();
}
public static class FooListener {
#RabbitListener(queues="foo")
public void pojoListener(String body,
#Header(required = false, name = "x-death") List<String> xDeath) {
System.out.println(body + ":" + (xDeath == null ? "" : xDeath));
}
}
}
Result:
Foo:[{reason=expired, count=1, exchange=, time=Thu Jun 02 08:44:19 EDT 2016, routing-keys=[bar], queue=bar}]

Answer 2

Gary's answer is the right one. Just a little detail, the type of xDeath is better to be ArrayList<HashMap<String,*>> instead List<String> xDeath. Then you can access any field by doing something like: xDeath.first().get("count")