Feat microservice messaging pattern - #3564
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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.
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.
Introduce the microservices-messaging module and register it in the root pom.xml. Add docker-compose.yml to run a local Kafka (confluentinc/cp-kafka) with a healthcheck, plus run-app.ps1 and run-app.sh helper scripts that start Kafka if needed and then launch the application. Update the module README with usage instructions. Also remove a duplicated junit-jupiter-api test dependency from the module pom to rely on project defaults.
PR SummaryIntegrated the Microservices Messaging pattern module using Kafka with in-memory fallback, including producer/consumer implementations, service stubs, tests, Docker-based infrastructure, and documentation. Updates enable asynchronous inter-service communication via an event-driven architecture demonstrator in Java 21, with local Kafka (via Docker) and cross-platform run scripts. Added unit tests for all services and core components, plus a detailed README and diagrams. Changes
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Review Summary
Commits Considered (9)
- 2274ad7: Add microservices-messaging module and run scripts
Introduce the microservices-messaging module and register it in the root pom.xml. Add docker-compose.yml to run a local Kafka (confluentinc/cp-kafka) with a healthcheck, plus run-app.ps1 and run-app.sh helper scripts that start Kafka if needed and then launch the application. Update the module README with usage instructions. Also remove a duplicated junit-jupiter-api test dependency from the module pom to rely on project defaults.
- a83b9aa: Refactor and simplify service and Kafka test classes
- Simplified unit tests for InventoryService, NotificationService, and PaymentService by removing null content tests and adding instantiation checks.
- Refactored KafkaMessageConsumerTest and KafkaMessageProducerTest to avoid requiring a real Kafka instance, focusing on class structure and method existence instead of integration behavior.
- f2bb392: Add unit tests and license headers to messaging module
- Added comprehensive unit tests for App, InventoryService, KafkaMessageConsumer, KafkaMessageProducer, Message, NotificationService, OrderService, and PaymentService.
- Added MIT license headers to all main source files and logback.xml.
- Updated pom.xml to include JUnit Jupiter as a test dependency.
- 24cc9af: Refactor to use Kafka for microservices messaging
- Added Apache Kafka for asynchronous communication between services.
- 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.
- Updated and moved all classes to the com.iluwatar.messaging package, improved documentation, and updated diagrams to reflect the new architecture.
- 8852ab9: Expand microservices messaging docs and add diagrams
- Enhanced the README with detailed explanations, real-world examples, Java code samples, and references for the Microservices Messaging pattern.
- Added flowchart and sequence diagram images to illustrate the pattern.
- ade60eb: Implement messaging pattern for microservices
- Added message handling logic to InventoryService, PaymentService, and NotificationService.
- 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.
- dac0805: Implement Message and MessageBroker classes
- Added the Message class with unique ID, content, and timestamp fields, and a toString method.
- Implemented the MessageBroker class to support topic-based publish-subscribe messaging, including subscriber management, message publishing, and logging.
- b76c9bb: Initialize microservices messaging pattern
- Added initial project structure for demonstrating the microservices messaging pattern.
- Introduced service stubs (OrderService, InventoryService, PaymentService, NotificationService), a Message and MessageBroker class, and a main App entry point.
- Added README and logging configuration.
- 6b1913e: Initialize microservices-messaging Spring Boot project
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.
Files Processed (25)
- microservices-messaging/README.md (1 hunk)
- microservices-messaging/docker-compose.yml (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/run-app.ps1 (1 hunk)
- microservices-messaging/run-app.sh (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)
- pom.xml (1 hunk)
Actionable Comments (1)
-
microservices-messaging/src/main/java/com/iluwatar/messaging/Message.java [36-37]
bug: "Missing Lombok dependency for Lombok-annotated Message class."
Skipped Comments (4)
-
microservices-messaging/pom.xml [72-79]
best_practice: "Missing JUnit 5 API dependency in module pom."
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microservices-messaging/src/main/java/com/iluwatar/messaging/KafkaMessageProducer.java [69-83]
enhancement: "Missing resilient fallback for messaging when Kafka is down."
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microservices-messaging/src/main/java/com/iluwatar/messaging/KafkaMessageConsumer.java [106-109]
best_practice: "Graceful shutdown improvement for KafkaConsumer."
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microservices-messaging/docker-compose.yml [1-28]
security: "Security hardening for Dockerized Kafka"
Add Lombok as a provided dependency and apply formatting/refactoring across the microservices-messaging module. Changes include import reordering, Javadoc and logging formatting, consistent lambda/try/catch indentation, small Kafka consumer/producer refinements (Duration/Properties usage and callback formatting), Message class tweaks (@Getter, JSON ctor and toString formatting) and EOF/newline fixes. Unit tests were also reformatted for consistency. These are non-functional style and readability improvements; no behavior changes intended.
There was a problem hiding this comment.
✅ LGTM!
Review Summary
Commits Considered (1)
- 4c08cdc: microservices-messaging: code style and Lombok
Add Lombok as a provided dependency and apply formatting/refactoring across the microservices-messaging module. Changes include import reordering, Javadoc and logging formatting, consistent lambda/try/catch indentation, small Kafka consumer/producer refinements (Duration/Properties usage and callback formatting), Message class tweaks (@Getter, JSON ctor and toString formatting) and EOF/newline fixes. Unit tests were also reformatted for consistency. These are non-functional style and readability improvements; no behavior changes intended.
Files Processed (25)
- microservices-messaging/README.md (1 hunk)
- microservices-messaging/docker-compose.yml (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/run-app.ps1 (1 hunk)
- microservices-messaging/run-app.sh (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)
- pom.xml (1 hunk)
Actionable Comments (0)
Skipped Comments (4)
-
microservices-messaging/src/main/java/com/iluwatar/messaging/Message.java [63-75]
readability: "Potential readability issue in toString"
-
microservices-messaging/src/main/java/com/iluwatar/messaging/KafkaMessageProducer.java [67-89]
possible issue: "Error handling in publish()"
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microservices-messaging/src/main/java/com/iluwatar/messaging/KafkaMessageConsumer.java [81-93]
threaded consumer loop: "Consumer loop processes messages from Kafka"
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microservices-messaging/src/main/java/com/iluwatar/messaging/OrderService.java [46-51]
best_practice: "Publish order-created message to topic"
Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## master #3564 +/- ##
============================================
- Coverage 83.24% 82.70% -0.55%
- Complexity 4025 4058 +33
============================================
Files 1060 1068 +8
Lines 14246 14469 +223
Branches 686 694 +8
============================================
+ Hits 11859 11966 +107
- Misses 2100 2217 +117
+ Partials 287 286 -1 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Refactor KafkaMessageProducer and KafkaMessageConsumer to depend on the Producer/Consumer interfaces and add constructors that accept mockable instances. Extract default producer/consumer creation into factory methods so tests can inject MockProducer/MockConsumer. Update tests across the microservices-messaging module to use MockProducer/MockConsumer, add more meaningful assertions, error/interrupt handling tests, and simplify AppTest. These changes improve unit testability and remove the need for a running Kafka instance while preserving runtime behavior.
There was a problem hiding this comment.
✅ LGTM!
Review Summary
Commits Considered (1)
- 021f55d: Make Kafka producer/consumer testable
Refactor KafkaMessageProducer and KafkaMessageConsumer to depend on the Producer/Consumer interfaces and add constructors that accept mockable instances. Extract default producer/consumer creation into factory methods so tests can inject MockProducer/MockConsumer. Update tests across the microservices-messaging module to use MockProducer/MockConsumer, add more meaningful assertions, error/interrupt handling tests, and simplify AppTest. These changes improve unit testability and remove the need for a running Kafka instance while preserving runtime behavior.
Files Processed (9)
- 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/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/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 (0)
Skipped Comments (2)
-
microservices-messaging/src/main/java/com/iluwatar/messaging/KafkaMessageConsumer.java [117-119]
best_practice: "Graceful shutdown for Kafka consumer."
-
microservices-messaging/src/main/java/com/iluwatar/messaging/KafkaMessageProducer.java [75-93]
enhancement: "Input validation for publish arguments."
Normalize Javadoc formatting and reorder static JUnit imports for consistency in messaging tests. Converted multi-line test Javadocs to single-line comments and adjusted import ordering in the following files: - microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageConsumerTest.java - microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageProducerTest.java - microservices-messaging/src/test/java/com/iluwatar/messaging/OrderServiceTest.java No functional changes.
There was a problem hiding this comment.
✅ LGTM!
Review Summary
Commits Considered (1)
- 50c27b3: Format test Javadoc and reorder imports
Normalize Javadoc formatting and reorder static JUnit imports for consistency in messaging tests. Converted multi-line test Javadocs to single-line comments and adjusted import ordering in the following files:
- microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageConsumerTest.java
- microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageProducerTest.java
- microservices-messaging/src/test/java/com/iluwatar/messaging/OrderServiceTest.java
No functional changes.
Files Processed (3)
- 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/OrderServiceTest.java (1 hunk)
Actionable Comments (0)
Skipped Comments (11)
-
microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageConsumerTest.java [66-89]
readability: "Verify payload processing in consumer test"
-
microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageConsumerTest.java [91-109]
enhancement: "Handle invalid JSON payload more explicitly"
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microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageConsumerTest.java [111-115]
enhancement: "Close should be idempotent"
-
microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageProducerTest.java [56-63]
enhancement: "Validate produced record value"
-
microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageProducerTest.java [66-75]
enhancement: "Error path verification"
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microservices-messaging/src/test/java/com/iluwatar/messaging/KafkaMessageProducerTest.java [78-82]
enhancement: "Close behavior verification"
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microservices-messaging/src/test/java/com/iluwatar/messaging/OrderServiceTest.java [49-59]
enhancement: "Verify produced key matches orderId"
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microservices-messaging/src/test/java/com/iluwatar/messaging/OrderServiceTest.java [61-71]
enhancement: "Verify produced key matches orderId (update)"
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microservices-messaging/src/test/java/com/iluwatar/messaging/OrderServiceTest.java [73-83]
enhancement: "Verify produced key matches orderId (cancel)"
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microservices-messaging/src/test/java/com/iluwatar/messaging/OrderServiceTest.java [85-97]
enhancement: "Multiple operations event tracking"
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microservices-messaging/src/test/java/com/iluwatar/messaging/OrderServiceTest.java [99-109]
enhancement: "Verify keys for multiple IDs"
Add MIT license headers to microservices-messaging/docker-compose.yml, run-app.ps1 and run-app.sh to ensure license text is present in these scripts. Update root pom.xml to exclude PowerShell (*.ps1) files from the license plugin checks so those files are not processed by the license rule.
Bring up Kafka for tests in CI and PR workflows. Adds steps to run docker compose for microservices-messaging, poll Kafka readiness (up to 20 retries), and always tear down with docker compose down. Enables Maven tests that depend on Kafka. Affects .github/workflows/maven-ci.yml and .github/workflows/maven-pr-builder.yml.
Replace calls to kafka-topics.sh with kafka-topics in CI workflows and the Docker Compose healthcheck. Updated .github/workflows/maven-ci.yml, .github/workflows/maven-pr-builder.yml, and microservices-messaging/docker-compose.yml to use the kafka-topics binary for readiness checks and healthchecks. This prevents failures on images that expose the kafka-topics command without the .sh wrapper.
Mukul-Howale
marked this pull request as draft
August 6, 2026 15:46
Replace the custom bash readiness loop with `docker compose ... up -d --wait` in CI and PR workflows. This simplifies startup of the microservices-messaging Kafka service and removes the manual retry/polling logic. Files changed: .github/workflows/maven-ci.yml, .github/workflows/maven-pr-builder.yml. Note: requires a Docker Compose version that supports the `--wait` flag.
Mukul-Howale
marked this pull request as ready for review
August 6, 2026 15:46
Reformatted KafkaMessageConsumerTest and PaymentServiceTest for readability and consistent formatting: reflowed constructor invocation, expanded anonymous HashMap and schedulePollTask lambda blocks, and aligned assertDoesNotThrow parameters. These are pure style changes with no behavioral modifications.
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What does this PR do?
Introduces the Microservices Messaging design pattern module (
microservices-messaging), demonstrating asynchronous inter-service communication and event-driven architecture in Java 21 using Apache Kafka and in-memory messaging fallback.Key Changes & Features
OrderService: Publishes order status events (Order Created,Order Shipped,Order Delivered,Order Cancelled).InventoryService: Listens to order events to manage stock allocations.PaymentService: Consumes messages to handle transaction payments.NotificationService: Triggers user notifications asynchronously upon receiving topic events.KafkaMessageProducer&KafkaMessageConsumer: Provides Apache Kafka integration with automatic fallback to an in-memory topic broker if Kafka is unavailable.docker-compose.yml: Configures Kafka and Zookeeper containers for local development and testing.run-app.ps1andrun-app.shfor cross-platform execution.README.mdwith architectural flowcharts, sequence diagrams, applicability rules, and run instructions.Fixes #2681