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RabbitMQ Messaging & Async Systems · Lección

Exchange Topic para un enrutamiento flexible

Domine el exchange Topic para crear patrones de enrutamiento complejos mediante coincidencias con comodines. Diseñe topologías de enrutamiento de mensajes flexibles y escalables.

Lección 3 de 411 pasos

Exchange Topic para un enrutamiento flexible es una lección gratuita de RabbitMQ Messaging & Async Systems en CoddyKit. Esta es la lección 3 de 4. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de RabbitMQ Messaging & Async Systems, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de RabbitMQ Messaging & Async Systems incluye 4 lecciones en total.

Partes de esta lección aún no han sido traducidas y se muestran en inglés.

Topic Exchange: Flexible Routing

Welcome to the Topic Exchange! This exchange type offers the most flexible message routing, letting you send messages to queues based on complex patterns.

Unlike the simple Fanout or direct-match Direct exchange, Topic exchanges use special wildcards in routing keys to match messages dynamically.

Understanding Topic Routing Keys

With a Topic exchange, routing keys aren't exact matches. They are strings made of words separated by dots (.), much like parts of a filename or URL.

  • Example: animal.rabbit.fast
  • Example: log.error.database

Each word provides a level of detail, allowing for hierarchical routing.

The Single-Word Wildcard: `*`

The asterisk (*) wildcard matches exactly one word in a routing key segment.

  • Binding key: animal.*.fast matches animal.rabbit.fast
  • Binding key: animal.*.fast does not match animal.dog.lazy.fast (too many words)
  • Binding key: *.error.* matches log.error.database

It's great for matching a specific position in the key.

The Zero-or-More Wildcard: `#`

The hash (#) wildcard matches zero or more words in a routing key. It's much more powerful than *.

  • Binding key: log.# matches log.error, log.info.web, log.debug.cache.entry
  • Binding key: animal.# matches animal.rabbit, animal.cat.sleepy

Use # to capture all messages that start with a certain pattern.

Producer: Declaring Topic Exchange

First, our producer needs to declare the Topic exchange. The type is simply "topic".

Try running this snippet to set up the exchange:

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

public class TopicProducerSetup {
    private static final String EXCHANGE_NAME = "topic_logs";

    public static void main(String[] argv) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost"); // Connect to local RabbitMQ
        try (Connection connection = factory.newConnection();
             Channel channel = connection.createChannel()) {

            channel.exchangeDeclare(EXCHANGE_NAME, "topic");
            System.out.println("Topic exchange '" + EXCHANGE_NAME + "' declared.");
        }
    }
}

Producer: Sending Messages

Now, let's send some messages using different routing keys. The exchange will use these keys to decide which queues receive the messages.

Notice how the keys are dot-separated, allowing for detailed categories.

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import java.nio.charset.StandardCharsets;

public class TopicMessageSender {
    private static final String EXCHANGE_NAME = "topic_logs";

    public static void main(String[] argv) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        try (Connection connection = factory.newConnection();
             Channel channel = connection.createChannel()) {

            channel.exchangeDeclare(EXCHANGE_NAME, "topic");

            sendMessage(channel, "animal.rabbit.fast", "A fast rabbit runs.");
            sendMessage(channel, "animal.cat.sleepy", "A sleepy cat naps.");
            sendMessage(channel, "log.error.db", "Database connection failed!");
            sendMessage(channel, "log.info.web", "User logged in.");

            System.out.println("Sent various topic messages.");
        }
    }

    private static void sendMessage(Channel channel, String routingKey, String message) throws Exception {
        channel.basicPublish(EXCHANGE_NAME, routingKey, null, message.getBytes(StandardCharsets.UTF_8));
        System.out.println(" [x] Sent '" + routingKey + ":'" + message + "'");
    }
}

Consumer: Binding with `*`

Consumers bind their queues to the Topic exchange using binding keys that can contain wildcards. This consumer uses *.orange.*.

It will receive messages like animal.orange.fast but not fruit.apple.sweet or animal.orange.

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.DeliverCallback;

public class TopicConsumerOrange {
    private static final String EXCHANGE_NAME = "topic_logs";

    public static void main(String[] argv) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        channel.exchangeDeclare(EXCHANGE_NAME, "topic");
        String queueName = channel.queueDeclare().getQueue();

        String bindingKey = "*.orange.*"; // Matches e.g., 'animal.orange.fast'
        channel.queueBind(queueName, EXCHANGE_NAME, bindingKey);
        System.out.println(" [x] Waiting for messages matching: '" + bindingKey + "'");

        DeliverCallback deliverCallback = (consumerTag, delivery) -> {
            String message = new String(delivery.getBody(), "UTF-8");
            System.out.println(" [x] Received '" + delivery.getEnvelope().getRoutingKey() + ":'" + message + "'");
        };
        channel.basicConsume(queueName, true, deliverCallback, consumerTag -> {});
    }
}

Consumer: Binding with `#`

This consumer uses the log.# binding key. This means it will receive all messages whose routing key starts with log., regardless of how many words follow.

This is extremely useful for systems like logging, where you might want a 'catch-all' listener for a category.

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.DeliverCallback;

public class TopicConsumerLogs {
    private static final String EXCHANGE_NAME = "topic_logs";

    public static void main(String[] argv) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        channel.exchangeDeclare(EXCHANGE_NAME, "topic");
        String queueName = channel.queueDeclare().getQueue();

        String bindingKey = "log.#"; // Matches e.g., 'log.error.db', 'log.info.web'
        channel.queueBind(queueName, EXCHANGE_NAME, bindingKey);
        System.out.println(" [x] Waiting for messages matching: '" + bindingKey + "'");

        DeliverCallback deliverCallback = (consumerTag, delivery) -> {
            String message = new String(delivery.getBody(), "UTF-8");
            System.out.println(" [x] Received '" + delivery.getEnvelope().getRoutingKey() + ":'" + message + "'");
        };
        channel.basicConsume(queueName, true, deliverCallback, consumerTag -> {});
    }
}

Topic Exchange Use Cases

Topic exchanges shine in scenarios requiring flexible and hierarchical routing:

  • Logging Systems: Route logs based on severity, source, and component (e.g., app.error.auth, app.info.payment).
  • Real-time Data Streams: Filter sensor data (e.g., sensor.room1.temp, sensor.room2.humidity).
  • Content Distribution: Deliver news articles to subscribers interested in specific categories or regions.

They provide fine-grained control over message flow.

Topic Routing Challenge

Consider the following messages and binding keys. Which messages will be delivered to a queue bound with the key animal.*.#.fast?

Responde en la lección interactiva

Recap: Topic Exchange Power

You've mastered the Topic exchange! It's an incredibly powerful tool for building flexible and scalable messaging architectures.

  • Uses dot-separated routing keys.
  • * matches exactly one word.
  • # matches zero or more words.
  • Ideal for logging, real-time analytics, and content filtering.

By using wildcards, you can create sophisticated routing rules to ensure messages go exactly where they're needed.

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Sí — el texto completo de «Exchange Topic para un enrutamiento flexible» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de RabbitMQ Messaging & Async Systems, actualiza a CoddyKit PRO. El curso de RabbitMQ Messaging & Async Systems incluye 4 lecciones en total.

¿Qué aprenderé en «Exchange Topic para un enrutamiento flexible»?

Domine el exchange Topic para crear patrones de enrutamiento complejos mediante coincidencias con comodines. Diseñe topologías de enrutamiento de mensajes flexibles y escalables. Practicas RabbitMQ Messaging & Async Systems con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.

¿Necesito experiencia previa para empezar RabbitMQ Messaging & Async Systems?

No se requiere experiencia previa. RabbitMQ Messaging & Async Systems en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 3 de 4.

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Todas las lecciones de este curso

  1. Exchange Fanout para Pub/Sub
  2. Exchange Direct para el enrutamiento
  3. Exchange Topic para un enrutamiento flexible
  4. Exchange predeterminado y bindings implícitos
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