* feat: add Microservices Bulkhead pattern (#3228)
* fix: cancel queued calls on bulkhead shutdown
Shutdown now cancels the queued futures so callers do not hang, a shutdown racing a submit is no longer counted as a rejection, and interrupted inventory checks are logged. The class diagram is a rendered PNG.
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Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
* feat: add Microservices Load Shedding pattern (#3229)
* fix: harden load shedder release and report the admitted count
release() clamps the in-flight count at zero, acquire() returns the admitted count that the service logs, and the demo summary reports the total shed. The class diagram is a rendered PNG.
* Add transactional-outbox module
Introduce a new transactional-outbox Maven module demonstrating the Transactional Outbox pattern. Adds a Spring Boot sample app and README explaining the pattern. New code includes Order and OutboxEvent entities, OrderStatus/EventStatus enums, Spring Data repositories (OrderRepository, OutboxRepository), OrderService (atomic write of order + outbox), OutboxPublisher (scheduled poll & publish), MessageBroker interface and MessageConsumer implementation, and App entrypoint. Includes unit tests (AppTest, OrderServiceTest, OutboxPublisherTest). Root pom.xml updated to register the new module. Module uses Spring Data JPA, Spring Web, Lombok, H2 and standard test dependencies.
* Add OutboxPublisher edge-case tests
Add two unit tests for OutboxPublisher: one verifies processOutboxEvents returns an empty list when there are no pending events; the other simulates a MessageBroker exception to ensure the event status is set to FAILED and the repository.save is called. Added necessary Mockito and assertion imports to support the tests.
* Use MockitoExtension for OutboxPublisher test
Replace the legacy inline/mock-based test with a JUnit5 + MockitoExtension unit test. Adds OutboxPublisherUnitTest (uses @ExtendWith(MockitoExtension.class), @Mock and @InjectMocks) that verifies broker exceptions mark events as FAILED and that the repository.save(...) is called. Removes the duplicate inline-mocking test and unused Mockito imports from OutboxPublisherTest.
* Replace Lombok @Slf4j with explicit Logger
Remove Lombok's @Slf4j and add explicit org.slf4j.Logger/LoggerFactory fields in transactional-outbox classes.
This makes logging explicit and removes reliance on Lombok's @Slf4j annotation.
* Add scheduled wrapper for outbox publishing
Introduce publishOutboxEvents() annotated with @Scheduled(fixedDelay = 5000) that delegates to the existing processOutboxEvents(). This separates the scheduling concern from the transactional processing method; processOutboxEvents() remains @Transactional and now only handles fetching and dispatching pending OutboxEvent items.
* Use UTC timestamps and add OutboxPublisher ctor
Use UTC for timestamps in OrderService and OutboxPublisher by switching LocalDateTime.now() to LocalDateTime.now(ZoneOffset.UTC). Replace Lombok @RequiredArgsConstructor on OutboxPublisher with an explicit constructor for dependency injection and remove the @Transactional annotation from processOutboxEvents. Update processedAt assignment to use UTC as well.
* 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.
* Initialize microservices messaging pattern
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.
* Implement Message and MessageBroker classes
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.
* Implement messaging pattern for microservices
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.
* Expand microservices messaging docs and add diagrams
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.
* Refactor to use Kafka for microservices messaging
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.
* Add unit tests and license headers to messaging module
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.
* 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.
* 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.
* 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.
* 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.
* 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.
* Add MIT headers and exclude .ps1 from license checks
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.
* Add Kafka docker service to CI workflows
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.
* Use kafka-topics instead of kafka-topics.sh
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.
* Use docker compose --wait for Kafka startup
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.
* Reformat tests for readability
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.
* Remove Kafka Docker Compose steps from CI
Removed the Start/Stop Kafka Docker Service steps that ran docker compose for microservices-messaging from .github/workflows/maven-ci.yml and .github/workflows/maven-pr-builder.yml. Workflows no longer start or tear down the Kafka docker-compose service during CI/PR runs; other steps (xvfb install, Maven build, Codecov upload, Sonar cache) remain unchanged.
* Bump google-java-format to 1.27.0; tidy tests
Update pom.xml to use google-java-format 1.27.0 (was 1.17.0). Make minor formatting cleanups in KafkaMessageConsumerTest and PaymentServiceTest by collapsing multi-line calls into single lines. No functional changes.
* Downgrade Google Java Format to 1.17.0
Update Spotless googleJavaFormat version in root pom.xml from 1.27.0 to 1.17.0
* Improve Kafka producer and consumer tests
Enhance microservices-messaging tests: add consumer tests to verify run() exits immediately when stopped and gracefully handles a WakeupException (ensuring the MockConsumer is closed). Update producer error test to avoid try-with-resources, assert publish behavior and history, trigger failingProducer.errorNext(...) before closing to cover the error callback branch, then close and assert the mock producer is closed.
* Refactor App.run and add messaging tests
Extract App.run(...) and introduce a package-private sleepMs field to control sleep durations so the demo can be exercised programmatically and sped up for tests. Main now delegates to run; consumers are started there. Tests updated: AppTest sets sleepMs to 0 and adds testRunWithMockObjects using MockProducer/MockConsumer to exercise run without a Kafka broker; KafkaMessageProducerTest adds a null-message publish test; minor formatting fix in KafkaMessageConsumerTest. These changes improve testability and coverage for the microservices-messaging module.
* Add Backends For Frontends pattern (#300)
Implements the BFF pattern with two client-specific gateways
(MobileBff, DesktopBff) aggregating shared downstream services
(AuthService, CartService, OrderService, SupplierService) into
client-tailored response shapes.
Closes#300
* Rename SupplierService lookup key to productName for clarity
The service is looked up by product name throughout the codebase, not
an actual product ID as the previous naming implied.
* Address review feedback: remove unnecessary compact constructors, add InMemory* service tests
Add an educational rule-engine module demonstrating the Rule Engine
pattern. Each business rule is an independent object exposing evaluate
(decision) and execute (action); a RuleEngine evaluates a collection of
rules against an immutable loan-application context in insertion order,
runs the passing rules, and reports every passed and failed rule via an
immutable RuleEngineResult. Includes three concrete rules, an App demo,
unit tests, README, and class diagram.
* feat: implement Immutable pattern #3448
Add immutable/ module with ImmutableUser (final class, defensive copy,
withAge wither method), App demo, JUnit 5 tests, PlantUML diagram, and
README following project conventions.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
* feat: add withName and withRoles wither methods to ImmutableUser #3448
Every field now has a corresponding wither for consistency.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
* fix: add junit-jupiter-api dependency to immutable module #3448
Required for @Test annotations and assert methods in test code.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
* added new microservice pattern polling-publisher, created folder structure, README.md & App.java
* added two service polling service & publisher service to handle two different operation & prepared initial skeleton
* polling-publisher service implementation
* fixed checkstyle errors
* subscriber-service implementation
* added entry point for subscriber service & unit test-case
* added unit test-case for DataSourceService class
* resolved dependency & structured classes
* implemented Data repository, DataSource Service & added unittest-case & implemented polling-service microservice
* implemented subscriber microservice using kafkaConsumer
* Fixed Kafka bug & added a controller to send message using API
* Fixed subscriber-service & updated pom.xml
* Fixed topic name
* added new listener for other topic
* updated all README.md
* added description on both application.yaml file
* added scope before class definition in Test classes & removed duplicate dependency from pom.xml & added required one
* added polling-publisher module in pom.xml
* Updated README.md file based on new template
* improved the README.md file & fixed it's format
* deleted unnecessary README.md files
* fixed the printing statements & used log function
* used logger to print statement
* addressed review comment: removed unnecessary dependency
* addressed review comment
* need to fix one test case shouldGraduallyIncreaseLimitWhenHealthy failing for AdaptiveRateLimiter.java
* Added Class Diagram and Flow Diagrams for Adaptive, Fixed Window and Token Bucket Rate Limiter
* Updated README.md. All test case passed. Updated with Google Java Guidelines
* Updated parent pom #2973
* Updated parent pom #2973
* fixed shouldResetCounterAfterWindow() test #2973
* formatting fixed#2973
* added test coverage for app.java and fixed random to be thread safe #2973
* added test coverage for app.java and fixed random to be thread safe #2973
* added test coverage for app.java and fixed random to be thread safe #2973
* added test coverage for app.java and fixed random to be thread safe #2973
* added test coverage for app.java and fixed random to be thread safe #2973
* added test coverage for app.java and fixed random to be thread safe #2973
* added test coverage for app.java and fixed random to be thread safe #2973
* fixed random to be thread safe #2973
* fixed random to be thread safe #2973
* fixed random to be thread safe #2973
* fixed spacing in pom.xml #2973
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Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
* #1263 - creating new module for view-helper
* #1263 - creating Product and ProductViewModel
* #1263 - creating interfaces for View and ViewHelper
* #1263 - creating ProductViewHelper and its test
* #1263 - creating Console View for Product
* #1263 - creating ProductController
* #1263 - creating main App and its test
* #1263 - adding license header
* #1263 - keeping module in alphabetical order
* #1263 - creating README and diagrams
* #1263 apply spotless
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Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
* Services and information
* README.md updated
* unit tests added for controllers
* pom.xml, clean up, java version update and slf4j logging added
* pom files updated
* Removed children maven wrappers
* Microservice-self-registration added to pom file
* POM file updated for self-registration
* pom file updated
* Update pom.xml
correction to mudule name
* SonarQube comments addressed
* sonarqube comments on coverage addressed
* Code coverage for custom health checks
* changes for unit tests
* changes for unit tests
* changes to for code coverage improvement
- Add implementation of Thread-Pool Executor pattern using hotel front desk example
- Include unit tests
- Create detailed README with pattern explanation and examples
- Add Java source code with appropriate Javadoc comments
Closes#3226
* feat: Implement Actor Model pattern #3232
* feat: Implement Actor Model pattern #3232
* feat: update Actor Model implementation with multi-actor logic #3251
* feat: update Actor Model implementation with multi-actor logic and loose coupling #3251
* test: add unit test for actor model #3251
* test: add test for App.java to increase coverage
* docs: add complete README for Actor Model pattern also implemented changes #3251
* remove spring dep
move junit, logging, mockito under dep mgmt
* upgrade anti-corruption-layer deps
* async method invocation
* balking, bloc
* bridge to bytecode
* caching
* callback - cqrs
* component - health check
* hexagonal - metadata mapping
* rest of the patterns
* remove checkstyle, take spotless into use
* Add Service Stub Pattern using Sentiment Analysis example
* Fix Checkstyle issues
* Suppress Sonar warning for Random usage in RealSentimentAnalysisServer
* added a pom.xml file for the monolithic structure, set up MVC file structure, and added basic model files using H2 database since its light and efficient
* added a pom.xml file for the monolithic structure, set up MVC file structure, and added basic model files using H2 database since its light and efficient
* Added "controllers" and repository classes to communicate with database to maintain code cleanliness
* added application.properties file for springboot, added controller classes and used the CLI main class from the previous submission and enhanced upon it
* fixed checkstyle comments
* fixed testing class
* automatically generated puml
* Readme File
Added Detailed Readme File in the md format
* attempting to fix some debugging issues
added more test cases, and tried to fix pom.xml
* dropped change
* another attempted fix
* added more test cases
* Fixes
Renamed the main module/directory. Added more content to the readme.md file. fixed the orElseThrow statements
Fixes
Renamed the main module/directory. Added more content to the readme.md file. fixed the orElseThrow statements
* fixed naming and readme file
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Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
* added bloC design pattern
* added bloC design pattern
* added Readme file
* fixed checkstyle warnings
* added tests for the ui
* fixed a test in MainTest file
* separating ui from main file and adding more tests
* added pom.xml plugins and properties and fixed readme.md
* fixed renaming problem and added context to main
* chsnged state class to record
* syncing changes for conflicts
* Revert "fixed conflicts"
* restored files
* renamed readme file and abstracted pom file
* Added Microservices client side ui composition to the repo.
Added ClientSideCompositionTest, ApiGateway, ClientSideIntegrator, FrontendComponent, CartFrontend, ProductFrontend, updated pom.xml, ReadME.md.
* Improved some checkstyle changes.
* Added Random variable to re-use the random instead of creating it everytime in FrontendComponent.
* changed the Pom.xml and upadted the ReadME.md
* Changes in the README.md File as per requirement, name of the file changed from ReadME.md to README.md
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Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
* pattern:implemented the Template View pattern (#1320)
* fix:added links in README and updated package name (#1320)
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Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
* Money pattern
the implementation of the money patter and the tests along with the read me file
* Update money/README.md
Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
* added App file anf modified README file and pom.xml file
* modified README and pom.xml
* added comments
* Added a test for App.java
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Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
