Add kafka4-migration module: Spring Kafka 3.3 to 4.1 migration on Boot 3.5 to 4.1

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Gth99spB1CzQmBFofXmU4Z

kafka4-migration/legacy/pom.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>org.springframework.boot</groupId>
+    <artifactId>spring-boot-starter-parent</artifactId>
+    <version>3.5.16</version>
+    <relativePath/>
+  </parent>
+  <groupId>com.ankurm</groupId>
+  <artifactId>kafka-legacy</artifactId>
+  <version>1.0.0</version>
+  <properties><java.version>21</java.version></properties>
+  <dependencies>
+    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency>
+    <dependency><groupId>org.springframework.kafka</groupId><artifactId>spring-kafka</artifactId></dependency>
+    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-json</artifactId></dependency>
+    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency>
+    <dependency><groupId>org.springframework.kafka</groupId><artifactId>spring-kafka-test</artifactId><scope>test</scope></dependency>
+  </dependencies>
+</project>

kafka4-migration/legacy/src/main/java/com/ankurm/kafka/App.java

@@ -0,0 +1,9 @@
+package com.ankurm.kafka;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class App {
+    public static void main(String[] args) { SpringApplication.run(App.class, args); }
+}

kafka4-migration/legacy/src/main/java/com/ankurm/kafka/OrderEvent.java

@@ -0,0 +1,3 @@
+package com.ankurm.kafka;
+
+public record OrderEvent(String id, int qty) { }

kafka4-migration/legacy/src/main/java/com/ankurm/kafka/OrderListener.java

@@ -0,0 +1,18 @@
+package com.ankurm.kafka;
+
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.List;
+import org.springframework.kafka.annotation.KafkaListener;
+import org.springframework.kafka.support.KafkaHeaders;
+import org.springframework.messaging.handler.annotation.Header;
+import org.springframework.stereotype.Component;
+
+@Component
+public class OrderListener {
+    public final List<String> received = new CopyOnWriteArrayList<>();
+
+    @KafkaListener(topics = "orders")
+    void on(OrderEvent event, @Header(KafkaHeaders.RECEIVED_KEY) String key) {
+        received.add("key=" + key + " id=" + event.id() + " qty=" + event.qty());
+    }
+}

kafka4-migration/legacy/src/main/java/com/ankurm/kafka/SerdeProbe.java

@@ -0,0 +1,14 @@
+package com.ankurm.kafka;
+
+import java.nio.charset.StandardCharsets;
+import org.springframework.kafka.support.serializer.JsonSerializer;
+
+/** Serialises one event with the JSON serializer, using only the runtime classpath (no test jars). */
+public class SerdeProbe {
+    public static void main(String[] args) {
+        try (JsonSerializer<OrderEvent> s = new JsonSerializer<>()) {
+            byte[] bytes = s.serialize("orders", new OrderEvent("o-1", 3));
+            System.out.println("SERIALIZED " + new String(bytes, StandardCharsets.UTF_8));
+        }
+    }
+}

kafka4-migration/legacy/src/main/resources/application.properties

@@ -0,0 +1,8 @@
+spring.kafka.consumer.group-id=orders-group
+spring.kafka.consumer.auto-offset-reset=earliest
+spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
+spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer
+spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
+spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
+spring.kafka.consumer.properties.spring.json.trusted.packages=com.ankurm.kafka
+spring.kafka.consumer.properties.spring.json.value.default.type=com.ankurm.kafka.OrderEvent

kafka4-migration/legacy/src/test/java/com/ankurm/kafka/OrderFlowTest.java

@@ -0,0 +1,27 @@
+package com.ankurm.kafka;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.awaitility.Awaitility.await;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.kafka.core.KafkaTemplate;
+import org.springframework.kafka.test.EmbeddedKafkaBroker;
+import org.springframework.kafka.test.context.EmbeddedKafka;
+
+@SpringBootTest(properties = "spring.kafka.bootstrap-servers=${spring.embedded.kafka.brokers}")
+@EmbeddedKafka(topics = "orders", partitions = 1)
+class OrderFlowTest {
+    @Autowired KafkaTemplate<String, OrderEvent> template;
+    @Autowired OrderListener listener;
+    @Autowired EmbeddedKafkaBroker broker;
+
+    @Test
+    void sendAndReceive() {
+        template.send("orders", "k1", new OrderEvent("o-1", 3));
+        await().untilAsserted(() -> assertThat(listener.received).hasSize(1));
+        System.out.println("RESULT " + listener.received.get(0));
+        System.out.println("BROKERS " + broker.getBrokersAsString().replaceAll(":\\d+", ":PORT"));
+    }
+}