Spring Boot RabbitMQ Receiver Jackson Deserialize to POJO

Question

I have a spring boot project where I'm trying to integrate with a rabbitmq server so I can publish and read messages to/from a queue.

Here's my rabbitmq config (edited to only show relevant details):

@Configuration
@ConfigurationProperties(prefix="rabbit")
public class RabbitConfig {
    private String queue;

    @Bean
    Queue queue() {
        return new Queue(queue, durable);
    }

    @Bean
    public MessageConverter jsonMessageConverter(){
        return new Jackson2JsonMessageConverter();
    }

    @Bean
    SimpleMessageListenerContainer container(ConnectionFactory connectionFactory, Queue queue,
                                             MessageListenerAdapter listenerAdapter, MessageConverter messageConverter) {
        SimpleMessageListenerContainer container = new SimpleMessageListenerContainer(connectionFactory);
        container.setQueues(queue);
        container.setMessageListener(listenerAdapter);
        container.setMessageConverter(messageConverter);
        return container;
    }

    @Bean
    MessageListenerAdapter listenerAdapter(Receiver receiver) {
        return new MessageListenerAdapter(receiver);
    }

    public void setQueue(String queue) {
        this.queue = queue;
    }
}

Here is my Receiver classes:

public interface Receiver {
    void handleMessage(FooA message);
}

@Component
public class RabbitReceiver implements Receiver {
    @Override
    public void handleMessage(FooA message) {
        System.out.println(message);
    }
}

And my pojo:

public class FooA {}
    private double num;
    private Map<String, String> map = new HashMap();

    public FooA() {
    }

    public FooA(double num, Map<String, String> map) {
        this.num = num;
        this.map = map;
    }

    public int getnum() {
        return num;
    }

    public Map<String, String> getMap() {
        return map;
    }
}

I am successfully able to publish a FooA message object to the queue. Here's what it looks like in the queue:

[
    {
        "payload_bytes": 41,
        "redelivered": false,
        "exchange": "amq.fanout",
        "routing_key": "",
        "message_count": 0,
        "properties": {
            "priority": 0,
            "delivery_mode": 2,
            "headers": {
                "__TypeId__": "com.test.FooA"
            },
            "content_encoding": "UTF-8",
            "content_type": "application/json"
        },
        "payload": "{\"num\":1.2,\"map\":{}}",
        "payload_encoding": "string"
    }
]

But when I try to read from the queue I get this error:

org.springframework.amqp.rabbit.listener.exception.ListenerExecutionFailedException: Failed to invoke target method 'handleMessage' with argument type = [class [B], value = [{[B@75a7bfc9}]
    at org.springframework.amqp.rabbit.listener.adapter.MessageListenerAdapter.invokeListenerMethod(MessageListenerAdapter.java:408) ~[spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.adapter.MessageListenerAdapter.onMessage(MessageListenerAdapter.java:298) ~[spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:822) ~[spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.invokeListener(AbstractMessageListenerContainer.java:745) ~[spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.access$001(SimpleMessageListenerContainer.java:97) [spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$1.invokeListener(SimpleMessageListenerContainer.java:189) ~[spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.invokeListener(SimpleMessageListenerContainer.java:1276) [spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.executeListener(AbstractMessageListenerContainer.java:726) ~[spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.doReceiveAndExecute(SimpleMessageListenerContainer.java:1219) [spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.receiveAndExecute(SimpleMessageListenerContainer.java:1189) [spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer.access$1500(SimpleMessageListenerContainer.java:97) [spring-rabbit-1.7.3.RELEASE.jar:na]
    at org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer$AsyncMessageProcessingConsumer.run(SimpleMessageListenerContainer.java:1421) [spring-rabbit-1.7.3.RELEASE.jar:na]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]
Caused by: java.lang.NoSuchMethodException: com.test.RabbitReceiver.handleMessage([B)
    at java.lang.Class.getMethod(Class.java:1786) ~[na:1.8.0_121]
    at org.springframework.util.MethodInvoker.prepare(MethodInvoker.java:174) ~[spring-core-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.amqp.rabbit.listener.adapter.MessageListenerAdapter.invokeListenerMethod(MessageListenerAdapter.java:386) ~[spring-rabbit-1.7.3.RELEASE.jar:na]
    ... 12 common frames omitted

What am I doing wrong?

Edit 1: I changed the method to:

@Override
public void handleMessage(byte[] message) {
    System.out.println(message);
}

Which worked but it's totally unusable. It just shows up like this:

How do I get this to map to my pojo FooA

Answer 1

This article shows how to solve this in an easier way: https://thepracticaldeveloper.com/produce-and-consume-json-messages-with-spring-boot-amqp/

Configuration:

@Bean
public RabbitTemplate rabbitTemplate(final ConnectionFactory connectionFactory) {
    final var rabbitTemplate = new RabbitTemplate(connectionFactory);
    rabbitTemplate.setMessageConverter(producerJackson2MessageConverter());
    return rabbitTemplate;
}

@Bean
public Jackson2JsonMessageConverter producerJackson2MessageConverter() {
    return new Jackson2JsonMessageConverter();
}

Listener:

@RabbitListener(queues = MessagingApplication.QUEUE_SPECIFIC_NAME)
public void receiveMessage(final CustomMessage customMessage) {
    log.info("Received message and deserialized to 'CustomMessage': {}", customMessage.toString());
}

POJO:

public record CustomMessage(@JsonProperty("text") String text,
                            @JsonProperty("priority") int priority,
                            @JsonProperty("secret") boolean secret)
        implements Serializable {
}

Answer 2

You are doing everything correctly. But you are not providing any method to MessageListenerAdapter to receive and process your message. That's why you are getting ListenerExecutionFailedException: Failed to invoke target method 'handleMessage' .

To fix this change the below code:

@Bean
    MessageListenerAdapter listenerAdapter(Receiver receiver) {
        return new MessageListenerAdapter(receiver);
    }

to:

@Bean
    MessageListenerAdapter listenerAdapter(Receiver receiver) {
        return new MessageListenerAdapter(receiver, "handleMessage");
    }

Answer 3

Convert the bytearray to a string and use jackson mapper (ObjectMapper) to map to your pojo. You have configurations on your mapper: e.g.

 this.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    this.configure(SerializationFeature.WRITE_NULL_MAP_VALUES, false);
    this.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);
    this.registerModule(new JavaTimeModule())

Answer 4

I just had the classes implement the Serializable interface removed the JsonMessageConverter. Json and Serializable was conflicting so it didn't work.

Answer 5

It looks like the message is posted as a String and not as JSON. Thats way you see

"payload_encoding": "string"

and Spring can automatically convert this string into to a byte[], as shown in the screenshot.

You need to set the message converter also on the RabbitTemplate like this :

@Bean
public RabbitTemplate rabbitTemplate(ConnectionFactory connectionFactory,MessageConverter rabbitJsonMessageConverter) {
    RabbitTemplate template = new RabbitTemplate(connectionFactory);
    template.setMessageConverter(rabbitJsonMessageConverter);
    return template;
}

This should correctly publish the message as JSON.