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();
}
}