Spring AMQP - Sender and Receiving Messages

Question

I am facing an issue in receiving a message from RabbitMQ. I am sending a message like below

        HashMap<Object, Object> senderMap=new HashMap<>();
        senderMap.put("STATUS", "SUCCESS");
        senderMap.put("EXECUTION_START_TIME", new Date());

        rabbitTemplate.convertAndSend(Constants.ADAPTOR_OP_QUEUE,senderMap);

If we see in RabbitMQ, we will get a fully qualified type.

In the current scenario, we have n number of producer for the same consumer. If i use any mapper, it leads to an exception. How will i send a message so that it doesn't contain any type_id and i can receive the message as Message object and later i can bind it to my custom object in the receiver.

I am receiving message like below. Could you please let me know how to use Jackson2MessageConverter so that message will get directly binds to my Object/HashMap from Receiver end. Also i have removed the Type_ID now from the sender.

How Message looks in RabbitMQ

priority: 0 delivery_mode: 2 headers:
ContentTypeId: java.lang.Object KeyTypeId: java.lang.Object content_encoding: UTF-8 content_type: application/json {"Execution_start_time":1473747183636,"status":"SUCCESS"}

@Component
public class AdapterOutputHandler {

    private static Logger logger = Logger.getLogger(AdapterOutputHandler.class);

    @RabbitListener(containerFactory="adapterOPListenerContainerFactory",queues=Constants.ADAPTOR_OP_QUEUE)
    public void handleAdapterQueueMessage(HashMap<String,Object> message){

        System.out.println("Receiver:::::::::::"+message.toString());

    }

}

Connection

@Bean(name="adapterOPListenerContainerFactory")
    public SimpleRabbitListenerContainerFactory adapterOPListenerContainerFactory() {
        SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
        factory.setConnectionFactory(connectionFactory());
        Jackson2JsonMessageConverter messageConverter = new Jackson2JsonMessageConverter();
        DefaultClassMapper classMapper = new DefaultClassMapper();
        messageConverter.setClassMapper(classMapper);
        factory.setMessageConverter(messageConverter);

    }

Exception

Caused by: org.springframework.amqp.support.converter.MessageConversionException: failed to convert Message content. Could not resolve __TypeId__ in header and no defaultType provided
    at org.springframework.amqp.support.converter.DefaultClassMapper.toClass(DefaultClassMapper.java:139)

I don't want to use __TYPE__ID from sender because they are multiple senders for the same queue and only one consumer.

Answer 1

it leads to an exception

What exception?

TypeId: com.diff.approach.JobListenerDTO

That means you are sending a DTO, not a hash map as you describe in the question.

If you want to remove the typeId header, you can use a message post processor...

rabbitTemplate.convertAndSend(Constants.INPUT_QUEUE, dto, m -> {
    m.getMessageProperties.getHeaders().remove("__TypeId__");
    return m;
});

(or , new MessagePostProcessor() {...} if you're not using Java 8).

EDIT

What version of Spring AMQP are you using? With 1.6 you don't even have to remove the __TypeId__ header - the framework looks at the listener parameter type and tells the Jackson converter the type so it automatically converts to that (if it can). As you can see here; it works fine without removing the type id...

package com.example;

import java.util.HashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

import org.springframework.amqp.core.Queue;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.amqp.rabbit.config.SimpleRabbitListenerContainerFactory;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.core.RabbitAdmin;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class So39443850Application {

    private static final String QUEUE = "so39443850";

    public static void main(String[] args) throws Exception {
        ConfigurableApplicationContext context = SpringApplication.run(So39443850Application.class, args);
        context.getBean(RabbitTemplate.class).convertAndSend(QUEUE, new DTO("baz", "qux"));
        context.getBean(So39443850Application.class).latch.await(10, TimeUnit.SECONDS);
        context.getBean(RabbitAdmin.class).deleteQueue(QUEUE);
        context.close();
    }

    private final CountDownLatch latch = new CountDownLatch(1);

    @RabbitListener(queues = QUEUE, containerFactory = "adapterOPListenerContainerFactory")
    public void listen(HashMap<String, Object> message) {
        System.out.println(message.getClass() + ":" + message);
        latch.countDown();
    }

    @Bean
    public Queue queue() {
        return new Queue(QUEUE);
    }

    @Bean
    public RabbitTemplate rabbitTemplate(ConnectionFactory connectionFactory) {
        RabbitTemplate template = new RabbitTemplate(connectionFactory);
        template.setMessageConverter(new Jackson2JsonMessageConverter());
        return template;
    }

    @Bean
    public SimpleRabbitListenerContainerFactory adapterOPListenerContainerFactory(ConnectionFactory connectionFactory) {
        SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
        factory.setConnectionFactory(connectionFactory);
        factory.setMessageConverter(new Jackson2JsonMessageConverter());
        return factory;
    }

    public static class DTO {

        private String foo;

        private String baz;

        public DTO(String foo, String baz) {
            this.foo = foo;
            this.baz = baz;
        }

        public String getFoo() {
            return this.foo;
        }

        public void setFoo(String foo) {
            this.foo = foo;
        }

        public String getBaz() {
            return this.baz;
        }

        public void setBaz(String baz) {
            this.baz = baz;
        }

    }

}

Result:

class java.util.HashMap:{foo=baz, baz=qux}

This is described in the documentation...

In versions prior to 1.6, the type information to convert the JSON had to be provided in message headers, or a custom ClassMapper was required. Starting with version 1.6, if there are no type information headers, the type can be inferred from the target method arguments.

You can also configure a custom ClassMapper to always return HashMap.