Message router

The following diagram provides an overview of the scenario that we will implement:

Let's say we have a service that triggers an event upon the creation of a new programming seminar, or hackathon, for a given community. We want to send all seminar events to a particular destination receiver and all hackaton events to another destination receiver. Moreover, we want to send messages to the same exchange. For that setup, a topic exchange is a rational choice; one queue will be bound to the topic exchange with the seminar.# routing key and another queue will be bound with hackaton.# routing key. The # character is special and serves as a pattern that matches any character sequence.

We can implement this type of message sending by further extending our Sender class:

private static final String SEMINAR_QUEUE = "seminar_queue";
private static final String HACKATON_QUEUE = "hackaton_queue";    
private static final String TOPIC_EXCHANGE = "topic_exchange";
    
public void sendEvent(String exchange, String message, String messageKey) {
    try {
        channel.exchangeDeclare(TOPIC_EXCHANGE, "topic");
        channel.queueDeclare(SEMINAR_QUEUE, false, false,                   false, null);
        channel.queueDeclare(HACKATON_QUEUE, false, false,                 false, null);
        channel.queueBind(SEMINAR_QUEUE, TOPIC_EXCHANGE,                 "seminar.#");
        channel.queueBind(HACKATON_QUEUE, TOPIC_EXCHANGE,                 "hackaton.#");
channel.basicPublish(TOPIC_EXCHANGE, messageKey, null,
        message.getBytes());
    } catch (IOException e) {
        LOGGER.error(e.getMessage(), e);
    }
}

In order to demonstrate event sending, we can use the TopicSenderDemo class:

public class TopicSenderDemo {

    private static final String TOPIC_EXCHANGE =                     "topic_exchange";

    public static void sendToTopicExchange() {
        Sender sender = new Sender();
        sender.initialize();
        sender.sendEvent(TOPIC_EXCHANGE, "Test message 1.",                     "seminar.java");
        sender.sendEvent(TOPIC_EXCHANGE, "Test message 2.",                     "seminar.rabbitmq");
        sender.sendEvent(TOPIC_EXCHANGE, "Test message 3.",                     "hackaton.rabbitmq");
        sender.destroy();
    }
    
    public static void main(String[] args) {
        sendToTopicExchange();
    }
}