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

* 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

polling-publisher/polling-service/etc/polling-service.urm.puml

@@ -0,0 +1,2 @@
+@startuml
+@enduml

polling-publisher/polling-service/pom.xml

@@ -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>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

@@ -0,0 +1,45 @@
+/*
+ * 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

@@ -0,0 +1,67 @@
+/*
+ * 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

@@ -0,0 +1,81 @@
+/*
+ * 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

@@ -0,0 +1,50 @@
+/*
+ * 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

@@ -0,0 +1,50 @@
+/*
+ * 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

@@ -0,0 +1,61 @@
+/*
+ * 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

@@ -0,0 +1,36 @@
+#
+# 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

@@ -0,0 +1,39 @@
+/*
+ * 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

@@ -0,0 +1,78 @@
+/*
+ * 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

@@ -0,0 +1,84 @@
+/*
+ * 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'.");
+  }
+}