Implementing Redis Key Expiration Notifications in Spring Boot to Auto‑Close Orders

Business scenario : When an order is created but not paid within a certain time, it should be automatically closed; polling tasks are inefficient because each order has a different creation time.

Implementation idea : Store a KV pair in Redis where the key is the order ID and the value can be arbitrary, set its TTL to 30 minutes, and listen for the key‑expiration event to trigger order cancellation.

Enable Redis key expiration notifications : Edit redis.conf and set notify-keyspace-events Ex (or append Ex to existing value). The letters represent event types, e.g., K for keyspace, E for keyevent, g for generic commands, x for expiration events, etc.

Dependency : Add the Redis starter to the Maven project.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

Configuration : Define a RedisListenerConfig class that creates a RedisMessageListenerContainer bean.

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;

@Configuration
public class RedisListenerConfig {
    @Bean
    RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        return container;
    }
}

Listener : Implement RedisKeyExpirationListener extending KeyExpirationEventMessageListener to receive expired‑key messages, extract the key, and perform order‑cancellation logic.

import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.listener.KeyExpirationEventMessageListener;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.stereotype.Component;

/**
 * Listens to all DB expiration events "__keyevent@*__:expired"
 */
@Component
public class RedisKeyExpirationListener extends KeyExpirationEventMessageListener {
    public RedisKeyExpirationListener(RedisMessageListenerContainer listenerContainer) {
        super(listenerContainer);
    }

    @Override
    public void onMessage(Message message, byte[] pattern) {
        // Get the expired key and handle order cancellation
        String expiredKey = message.toString();
        System.out.println(expiredKey);
        // TODO: locate order by key and update its status to closed
    }
}

With this setup, when the Redis key representing an unpaid order expires after 30 minutes, the listener receives the event, retrieves the order ID, and updates the order status to closed, eliminating the need for frequent polling.