feat: Microservice Messaging Pattern (#2681) by Mukul-Howale · Pull Request #3421 · iluwatar/java-design-patterns · GitHub
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feat: Microservice Messaging Pattern (#2681)#3421

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feat: Microservice Messaging Pattern (#2681)#3421
Mukul-Howale wants to merge 8 commits into
iluwatar:masterfrom
Mukul-Howale:master

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@Mukul-Howale

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Issue : #2681

Add initial project structure for microservices-messaging using Spring Boot. Includes Maven configuration with dependencies for Kafka, Lombok, and testing, as well as main application, test class, and application properties.
1. Added initial project structure for demonstrating the microservices messaging pattern.
2. Introduced service stubs (OrderService, InventoryService, PaymentService, NotificationService), a Message and MessageBroker class, and a main App entry point.
3. Added README and logging configuration.
1. Added the Message class with unique ID, content, and timestamp fields, and a toString method.
2. Implemented the MessageBroker class to support topic-based publish-subscribe messaging, including subscriber management, message publishing, and logging.
1. Added message handling logic to InventoryService, PaymentService, and NotificationService.
2. OrderService now publishes order events to a MessageBroker, and App demonstrates the messaging workflow. 3. Each service processes relevant order events and logs actions for demonstration purposes.
1. Enhanced the README with detailed explanations, real-world examples, Java code samples, and references for the Microservices Messaging pattern.
2. Added flowchart and sequence diagram images to illustrate the pattern.
1. Added Apache Kafka for asynchronous communication between services.
2. Added KafkaMessageProducer and KafkaMessageConsumer classes, updated service implementations and main application logic to use Kafka, and adjusted the Maven configuration to include Kafka and Jackson dependencies.
3. Updated and moved all classes to the com.iluwatar.messaging package, improved documentation, and updated diagrams to reflect the new architecture.
1. Added comprehensive unit tests for App, InventoryService, KafkaMessageConsumer, KafkaMessageProducer, Message, NotificationService, OrderService, and PaymentService.
2. Added MIT license headers to all main source files and logback.xml.
3. Updated pom.xml to include JUnit Jupiter as a test dependency.
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github-actions Bot commented Jan 21, 2026

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1. Simplified unit tests for InventoryService, NotificationService, and PaymentService by removing null content tests and adding instantiation checks.
2. Refactored KafkaMessageConsumerTest and KafkaMessageProducerTest to avoid requiring a real Kafka instance, focusing on class structure and method existence instead of integration behavior.

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🚨 Pull request needs attention.

Review Summary

Commits Considered (1)
  • 98e442e: Refactor and simplify service and Kafka test classes
  1. Simplified unit tests for InventoryService, NotificationService, and PaymentService by removing null content tests and adding instantiation checks.
  2. Refactored KafkaMessageConsumerTest and KafkaMessageProducerTest to avoid requiring a real Kafka instance, focusing on class structure and method existence instead of integration behavior.
Files Processed (21)
  • microservices-messaging/README.md (1 hunk)
  • microservices-messaging/etc/microservices-messaging-flowchart.png (0 hunks)
  • microservices-messaging/etc/microservices-messaging-sequence-diagram.png (0 hunks)
  • microservices-messaging/pom.xml (1 hunk)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/App.java (1 hunk)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/InventoryService.java (1 hunk)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/KafkaMessageConsumer.java (1 hunk)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/KafkaMessageProducer.java (1 hunk)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/Message.java (1 hunk)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/NotificationService.java (1 hunk)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/OrderService.java (1 hunk)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/PaymentService.java (1 hunk)
  • microservices-messaging/src/main/resources/logback.xml (1 hunk)
  • microservices-messaging/src/test/java/com/iluwatar/messaging/AppTest.java (1 hunk)
  • microservices-messaging/src/test/java/com/iluwatar/messaging/InventoryServiceTest.java (1 hunk)
  • microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageConsumerTest.java (1 hunk)
  • microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageProducerTest.java (1 hunk)
  • microservices-messaging/src/test/java/com/iluwatar/messaging/MessageTest.java (1 hunk)
  • microservices-messaging/src/test/java/com/iluwatar/messaging/NotificationServiceTest.java (1 hunk)
  • microservices-messaging/src/test/java/com/iluwatar/messaging/OrderServiceTest.java (1 hunk)
  • microservices-messaging/src/test/java/com/iluwatar/messaging/PaymentServiceTest.java (1 hunk)
Actionable Comments (1)
  • microservices-messaging/src/main/java/com/iluwatar/messaging/Message.java [36-37]

    bug: "Missing Lombok-based getters for Message"

Skipped Comments (0)

@sonarqubecloud

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@Mukul-Howale Mukul-Howale marked this pull request as ready for review January 21, 2026 17:41
@Mukul-Howale

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@iluwatar Please review!

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This PR is stale because it has been open 60 days with no activity.

@github-actions github-actions Bot added the Stale label Mar 24, 2026

@iluwatar iluwatar left a comment

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The new module has not been added to the parent pom.xml and that's why CI is not building it currently

@iluwatar iluwatar left a comment

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Building with tests is broken

* </pre>
*/
public class App {
private static final Logger LOGGER = LoggerFactory.getLogger(App.class);

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Use Lombok annotation for logging

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This class does not exist in the code

@github-actions github-actions Bot removed the Stale label Jun 4, 2026

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You need to add the new module to parent pom.xml, otherwise it's not built by CI

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