Event-Driven Architecture: Patterns, Brokers, and Production Strategies

package io.thecodeforge.eda.models;

import java.time.Instant;
import java.util.UUID;

/**
 * io.thecodeforge: Standardizing Intent vs Fact
 */
public class CommunicationPatterns {

    // COMMAND: Targeted intent. High coupling. 
    // If the receiver is gone, the intent fails.
    public record RegisterUserCommand(
        UUID commandId,
        String email,
        String plainTextPassword
    ) {}

    // EVENT: Immutable fact. Zero coupling. 
    // Multiple services (Audit, Email, Analytics) can 'sub' to this.
    public record UserRegisteredEvent(
        UUID eventId,
        UUID userId,
        String email,
        Instant occurredAt
    ) {}

    // QUERY: Immediate data request (REST/gRPC).
    public record GetUserProfileQuery(UUID userId) {}
}

package io.thecodeforge.eda.kafka;

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerRecord;
import java.util.Properties;

public class TheCodeForgeProducer {
    
    public void publishUserEvent(String userId, String payload) {
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

        try (KafkaProducer<String, String> producer = new KafkaProducer<>(props)) {
            // Partitioning by userId ensures all events for ONE user 
            // land in the same partition, preserving sequence order.
            ProducerRecord<String, String> record = 
                new ProducerRecord<>("io.thecodeforge.user-events", userId, payload);
            
            producer.send(record, (metadata, exception) -> {
                if (exception == null) {
                    System.out.printf("Event persisted to topic %s partition %d%n", 
                        metadata.topic(), metadata.partition());
                }
            });
        }
    }
}