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#2673: feat: Microservice pattern: Polling publisher #3243 (#3292)

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* 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
This commit is contained in:
Aditya Kumawat
2026-05-31 17:54:58 +03:00
committed by GitHub
parent f7ad42dc05
commit 318130c486
22 changed files with 1099 additions and 0 deletions
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polling-publisher/README.md
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---
title: "Polling Publisher-Subscriber Pattern in Java: Mastering Asynchronous Messaging Elegantly"
shortTitle: Polling Pub/Sub
description: "Learn how to implement a Polling Publisher-Subscriber system in Java using Spring Boot and Kafka. Explore the architecture, real-world analogies, and benefits of asynchronous communication with clean code examples."
category: Architectural
language: en
tag:
- Spring Boot
- Kafka
- Microservices
- Asynchronous Messaging
- Decoupling
---
## Also known as
* Event-Driven Architecture
* Asynchronous Pub/Sub Pattern
* Message Queue-Based Polling System
## Intent of Polling Publisher-Subscriber Pattern
The Polling Publisher-Subscriber pattern decouples data producers from consumers by enabling asynchronous, message-driven communication. A service polls a data source and publishes messages to a message broker (e.g., Kafka), which are then consumed by one or more subscriber services.
## Detailed Explanation of the Pattern with Real-World Examples
### Real-world analogy
> A news agency constantly polls for the latest news updates. Once it receives new information, it publishes them to different news outlets (TV, newspapers, apps). Each outlet consumes and displays the updates independently.
### In plain words
> One service regularly checks for updates (polls) and sends messages to Kafka. Another service listens to Kafka and processes the messages asynchronously.
### Wikipedia says
> This pattern closely resembles the [Publish–subscribe model](https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern), where messages are sent by publishers and received by subscribers without them knowing each other.
### Architecture Flow
```
+------------+ +--------+ +-------------+
| Publisher | ---> | Kafka | ---> | Subscriber |
+------------+ +--------+ +-------------+
```
## Programmatic Example (Spring Boot + Kafka)
### Publisher Service
- Uses Spring's `@Scheduled` to poll data periodically.
- Publishes data to a Kafka topic.
- Optionally exposes a REST API for manual data publishing.
```java
@Scheduled(fixedRate = 5000)
public void pollAndPublish() {
String data = pollingService.getLatestData();
kafkaTemplate.send("updates-topic", data);
}
```
### Subscriber Service
- Listens to Kafka topic using `@KafkaListener`.
- Processes messages asynchronously.
```java
@KafkaListener(topics = "updates-topic")
public void processUpdate(String message) {
log.info("Received update: {}", message);
updateProcessor.handle(message);
}
```
## When to Use the Polling Publisher-Subscriber Pattern
Use this pattern when:
* Real-time push from the producer is not possible.
* Loose coupling between producers and consumers is desired.
* You need asynchronous, scalable event processing.
* You are building an event-driven microservices architecture.
## Real-World Applications
* Real-time reporting dashboards
* Health check aggregators for distributed systems
* IoT telemetry processing
* Notification and alerting systems
## Benefits and Trade-offs of Polling Pub/Sub Pattern
### Benefits
* Loose coupling between services
* Asynchronous and scalable architecture
* Fault-tolerant with message persistence in Kafka
* Easy to extend with new consumers or publishers
### Trade-Offs
* Polling introduces latency between data generation and consumption
* Requires managing and configuring Kafka (or other brokers)
* Slightly more complex deployment and infrastructure setup
## Related Java Design Patterns
* [Observer Pattern](https://java-design-patterns.com/patterns/observer/)
* [Mediator Pattern](https://java-design-patterns.com/patterns/mediator/)
* [Message Queue Pattern](https://java-design-patterns.com/patterns/event-queue/)
## References and Credits
* [Apache Kafka Documentation](https://kafka.apache.org/documentation/)
* [Spring Kafka Documentation](https://docs.spring.io/spring-kafka)
* [Spring Scheduled Tasks](https://www.baeldung.com/spring-scheduled-tasks)
* [Spring Kafka Tutorial – Baeldung](https://www.baeldung.com/spring-kafka)
* Inspired by: [iluwatar/java-design-patterns](https://github.com/iluwatar/java-design-patterns)
polling-publisher/etc/polling-publisher.urm.puml
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@startuml
@enduml
polling-publisher/polling-service/etc/polling-service.urm.puml
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@startuml
@enduml
polling-publisher/polling-service/pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<!--
This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
The MIT License
Copyright © 2014-2022 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>polling-publisher</artifactId>
<version>1.26.0-SNAPSHOT</version>
</parent>
<artifactId>polling-service</artifactId>
<packaging>jar</packaging>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<configuration>
<archive>
<manifest>
<mainClass>com.iluwatar.polling-service.App</mainClass>
</manifest>
</archive>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
polling-publisher/polling-service/src/main/java/com/iluwatar/polling/App.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableScheduling;
/** Polling-Publisher pattern paradigm. */
@SpringBootApplication
@EnableScheduling
public class App {
/**
* Program entry point.
*
* @param args command line args.
*/
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
polling-publisher/polling-service/src/main/java/com/iluwatar/polling/DataRepository.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import java.util.HashMap;
import java.util.Map;
import javax.annotation.PostConstruct;
import org.springframework.stereotype.Repository;
/** Data repository to keep or store data. */
@Repository
public class DataRepository {
private final Map<Integer, String> dataStorage = new HashMap<>();
/** init after map creation ... to put dummy data. */
@PostConstruct
public void init() {
// Injecting dummy data at startup
dataStorage.put(2, "Initial Dummy Data - two - 2");
dataStorage.put(3, "Initial Dummy Data - three - 3");
dataStorage.put(4, "Initial Dummy Data - four - 4");
}
/** Save data to the repository. */
public void save(int id, String value) {
dataStorage.put(id, value);
}
/** Retrieve data by ID. */
public String findById(int id) {
return dataStorage.getOrDefault(id, "Data not found");
}
/** Delete data by ID. */
public void delete(int id) {
dataStorage.remove(id);
}
/** Get all data. */
public Map<Integer, String> findAll() {
return dataStorage;
}
}
polling-publisher/polling-service/src/main/java/com/iluwatar/polling/DataSourceService.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
/** This class is responsible for keeping the events. */
@Service
public class DataSourceService {
private static final Logger log = LoggerFactory.getLogger(DataSourceService.class);
private final DataRepository repository;
private final ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
/** Constructor & Scheduler to push random data. */
public DataSourceService(DataRepository repository) {
this.repository = repository;
scheduleDataGeneration();
}
private void scheduleDataGeneration() {
Random random = new Random();
scheduler.scheduleAtFixedRate(
() -> {
int id = random.nextInt(100); // Random ID
String value = "Auto-Data-" + id;
this.addData(id, value);
log.info("🔵 Data Added: {} -> {}", id, value);
},
0,
3,
TimeUnit.SECONDS);
}
public void addData(int id, String value) {
repository.save(id, value);
}
public String getData(int id) {
return repository.findById(id);
}
public void removeData(int id) {
repository.delete(id);
}
public Map<Integer, String> getAllData() {
return repository.findAll();
}
}
polling-publisher/polling-service/src/main/java/com/iluwatar/polling/KafkaProducer.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.stereotype.Component;
/** This class is responsible for sending messages to Kafka. */
@Component
public class KafkaProducer {
@Autowired private final KafkaTemplate<String, String> kafkaTemplate;
public KafkaProducer(KafkaTemplate<String, String> kafkaTemplate) {
this.kafkaTemplate = kafkaTemplate;
}
/**
* Sends a message to the Kafka topic.
*
* @param message The message to send.
*/
public void sendMessage(String topic, String message) {
kafkaTemplate.send(topic, message);
}
}
polling-publisher/polling-service/src/main/java/com/iluwatar/polling/PollingController.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
/** This class is responsible for contolling polling tasks. */
@RestController
public class PollingController {
@Autowired private KafkaProducer kafkaProducer;
@GetMapping("/health")
public String healthCheck() {
return "Polling Service is up and running!";
}
@PostMapping("/send")
public String sendMessage(@RequestParam("message") String message) {
kafkaProducer.sendMessage("API", message);
return "Message sent: " + message;
}
}
polling-publisher/polling-service/src/main/java/com/iluwatar/polling/PollingScheduler.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import java.util.Random;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
/** This class is responsible for scheduling polling tasks. */
@Component
public class PollingScheduler {
private static final Logger log = LoggerFactory.getLogger(PollingScheduler.class);
@Autowired private DataSourceService dataSourceService;
@Autowired private KafkaProducer kafkaProducer;
/** Scheduler for poll data on each 5 second. */
@Scheduled(fixedRate = 5000) // Poll every 5 seconds
public void pollDataSource() {
try {
int id = new Random().nextInt(100); // Pick a random ID
String data = dataSourceService.getData(id); // Get data from service
if (data != null) {
log.info("🟢 Publishing Data: {}", data);
kafkaProducer.sendMessage("updates", data);
} else {
log.info("🔴 No Data Found for ID: {}", id);
}
} catch (Exception e) {
log.error("Error while publishing data {}", e.getMessage());
throw new RuntimeException(e);
}
}
}
polling-publisher/polling-service/src/main/resources/application.yml
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#
# This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
#
# The MIT License
# Copyright © 2014-2022 Ilkka Seppälä
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
server:
port: 8081
spring:
kafka:
bootstrap-servers: localhost:9092 # Kafka broker address(es)
consumer:
group-id: subscriber-group # Consumer group ID
auto-offset-reset: earliest # How to reset offset on consumer startup
# Add other consumer properties here
polling-publisher/polling-service/src/test/java/com/iluwatar/polling/AppTest.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import static org.junit.jupiter.api.Assertions.*;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
@SpringBootTest
public class AppTest {
@Test
void polling() {
assertDoesNotThrow(() -> App.main(new String[] {}));
}
}
polling-publisher/polling-service/src/test/java/com/iluwatar/polling/DataRepositoryTest.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import static org.junit.jupiter.api.Assertions.*;
import java.util.Map;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
public class DataRepositoryTest {
private DataRepository repository;
@BeforeEach
void setUp() {
repository = new DataRepository(); // Initialize before each test
}
@Test
void testSaveAndFindById() {
repository.save(1, "Test Data");
String result = repository.findById(1);
assertEquals("Test Data", result, "The retrieved data should match the stored value.");
}
@Test
void testFindById_NotFound() {
String result = repository.findById(99);
assertEquals("Data not found", result, "Should return 'Data not found' for missing entries.");
}
@Test
void testDelete() {
repository.save(2, "To be deleted");
repository.delete(2);
String result = repository.findById(2);
assertEquals("Data not found", result, "Deleted data should not be retrievable.");
}
@Test
void testFindAll() {
repository.save(1, "First");
repository.save(2, "Second");
Map<Integer, String> allData = repository.findAll();
assertEquals(2, allData.size(), "The repository should contain two items.");
assertTrue(allData.containsKey(1) && allData.containsKey(2), "Both keys should exist.");
}
}
polling-publisher/polling-service/src/test/java/com/iluwatar/polling/DataSourceServiceTest.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.polling;
import static org.junit.jupiter.api.Assertions.*;
import java.util.Map;
import org.junit.jupiter.api.*;
public class DataSourceServiceTest {
private DataRepository repository;
private DataSourceService service;
@BeforeEach
void setUp() {
repository = new DataRepository();
service = new DataSourceService(repository);
}
@Test
void testAddData() {
service.addData(1, "Test Data");
assertEquals("Test Data", repository.findById(1));
}
@Test
void testGetData() {
repository.save(1, "Test Data");
String result = service.getData(1);
assertEquals("Test Data", result, "The retrieved data should match.");
}
@Test
void testRemoveData() {
repository.save(2, "Some Data");
service.removeData(2);
assertEquals(
"Data not found", repository.findById(2), "Deleted data should not be retrievable.");
}
@Test
void testGetAllData() {
Map<Integer, String> result = service.getAllData();
int size = result.size();
repository.save(1, "First");
repository.save(2, "Second");
Map<Integer, String> result1 = service.getAllData();
assertEquals(size + 2, result.size(), "Should return all stored data.");
assertEquals("First", result.get(1), "Value for key 1 should be 'First'.");
assertEquals("Second", result.get(2), "Value for key 2 should be 'Second'.");
}
}
polling-publisher/pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<!--
This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
The MIT License
Copyright © 2014-2022 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.26.0-SNAPSHOT</version>
</parent>
<artifactId>polling-publisher</artifactId>
<packaging>pom</packaging>
<modules>
<module>polling-service</module>
<module>subscriber-service</module>
</modules>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>${spring-boot.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<version>${spring-boot.version}</version>
</dependency>
<!-- Spring Boot Test -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<version>${spring-boot.version}</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.kafka/spring-kafka -->
<dependency>
<groupId>org.springframework.kafka</groupId>
<artifactId>spring-kafka</artifactId>
<version>3.3.2</version>
</dependency>
<dependency>
<groupId>org.springframework.kafka</groupId>
<artifactId>spring-kafka-test</artifactId>
<version>3.3.2</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot</artifactId>
<version>${spring-boot.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/javax.annotation/javax.annotation-api -->
<dependency>
<groupId>javax.annotation</groupId>
<artifactId>javax.annotation-api</artifactId>
<version>1.3.2</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>1.5.18</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.5.18</version>
</dependency>
</dependencies>
</project>
polling-publisher/subscriber-service/etc/subscriber-service.urm.puml
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@startuml
@enduml
polling-publisher/subscriber-service/pom.xml
+59
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@@ -0,0 +1,59 @@
<?xml version="1.0" encoding="UTF-8"?>
<!--
This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
The MIT License
Copyright © 2014-2022 Ilkka Seppälä
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>polling-publisher</artifactId>
<version>1.26.0-SNAPSHOT</version>
</parent>
<artifactId>subscriber-service</artifactId>
<packaging>jar</packaging>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<configuration>
<archive>
<manifest>
<mainClass>com.iluwatar.subscriber-service.App</mainClass>
</manifest>
</archive>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
polling-publisher/subscriber-service/src/main/java/com/iluwatar/subscriber/App.java
+37
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.subscriber;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/** Polling-Publisher pattern paradigm. */
@SpringBootApplication
public class App {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
polling-publisher/subscriber-service/src/main/java/com/iluwatar/subscriber/KafkaConsumer.java
+48
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.subscriber;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.stereotype.Service;
/** Kafka consumer service to consume messages / updates. */
@Service
public class KafkaConsumer {
private static final Logger log = LoggerFactory.getLogger(KafkaConsumer.class);
@KafkaListener(topics = "updates", groupId = "subscriber-group")
public void listenUpdates(String message) {
log.info("[updates]: Received message: {}", message);
}
@KafkaListener(topics = "API", groupId = "subscriber-group")
public void listenApi(String message) {
log.info("[API]: Received message from /send : {}", message);
}
}
polling-publisher/subscriber-service/src/main/resources/application.yml
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#
# This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
#
# The MIT License
# Copyright © 2014-2022 Ilkka Seppälä
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
server:
port: 8082
spring:
kafka:
bootstrap-servers: localhost:9092 # Kafka broker address(es)
consumer:
group-id: subscriber-group
polling-publisher/subscriber-service/src/test/java/com/iluwatar/subscriber/AppTest.java
+40
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@@ -0,0 +1,40 @@
/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.subscriber;
import static org.junit.jupiter.api.Assertions.*;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
@SpringBootTest
public class AppTest {
@Test
void subscriber() {
assertDoesNotThrow(() -> App.main(new String[] {}));
}
}
pom.xml
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@@ -191,6 +191,7 @@
<module>partial-response</module>
<module>pipeline</module>
<module>poison-pill</module>
<module>polling-publisher</module>
<module>presentation-model</module>
<module>private-class-data</module>
<module>producer-consumer</module>