BAEL3889 - Kafka Mock Producer

libraries/src/main/java/com/baeldung/kafka/EvenOddPartitioner.java

@@ -0,0 +1,16 @@
+package com.baeldung.kafka;
+
+import org.apache.kafka.clients.producer.internals.DefaultPartitioner;
+import org.apache.kafka.common.Cluster;
+
+public class EvenOddPartitioner extends DefaultPartitioner {
+
+    @Override
+    public int partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes, Cluster cluster) {
+
+        if (((String)key).length() % 2 == 0)
+            return 0;
+
+        return 1;
+    }
+}

libraries/src/main/java/com/baeldung/kafka/KafkaProducer.java

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+package com.baeldung.kafka;
+
+import org.apache.kafka.clients.producer.Producer;
+import org.apache.kafka.clients.producer.ProducerRecord;
+import org.apache.kafka.clients.producer.RecordMetadata;
+
+import java.util.concurrent.Future;
+
+public class KafkaProducer {
+
+    private final Producer<String, String> producer;
+
+    public KafkaProducer(Producer<String, String> producer) {
+        this.producer = producer;
+    }
+
+    public Future<RecordMetadata> send(String key, String value) {
+        ProducerRecord record = new ProducerRecord("topic_sports_news",
+                key, value);
+        return producer.send(record);
+    }
+
+    public void flush() {
+        producer.flush();
+    }
+
+    public void beginTransaction() {
+        producer.beginTransaction();
+    }
+
+    public void initTransaction() {
+        producer.initTransactions();
+    }
+
+    public void commitTransaction() {
+        producer.commitTransaction();
+    }
+
+
+}

libraries/src/test/java/com/baeldung/kafka/KafkaProducerUnitTest.java

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+package com.baeldung.kafka;
+
+import org.apache.kafka.clients.producer.MockProducer;
+import org.apache.kafka.clients.producer.RecordMetadata;
+import org.apache.kafka.common.Cluster;
+import org.apache.kafka.common.Node;
+import org.apache.kafka.common.PartitionInfo;
+import org.apache.kafka.common.serialization.StringSerializer;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+
+import static java.util.Collections.emptySet;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class KafkaProducerUnitTest {
+
+    private final String TOPIC_NAME = "topic_sports_news";
+
+    private KafkaProducer kafkaProducer;
+    private MockProducer<String, String> mockProducer;
+
+    private void buildMockProducer(boolean autoComplete) {
+        this.mockProducer = new MockProducer<>(autoComplete, new StringSerializer(), new StringSerializer());
+    }
+
+    @Test
+    void givenKeyValue_whenSend_thenVerifyHistory() throws ExecutionException, InterruptedException {
+
+        buildMockProducer(true);
+        //when
+        kafkaProducer = new KafkaProducer(mockProducer);
+        Future<RecordMetadata> recordMetadataFuture = kafkaProducer.send("data", "{\"site\" : \"baeldung\"}");
+
+        //then
+        assertTrue(mockProducer.history().size() == 1);
+        assertTrue(mockProducer.history().get(0).key().equalsIgnoreCase("data"));
+        assertTrue(recordMetadataFuture.get().partition() == 0);
+
+    }
+
+    @Test
+    void givenKeyValue_whenSend_thenSendOnlyAfterFlush() {
+
+        buildMockProducer(false);
+        //when
+        kafkaProducer = new KafkaProducer(mockProducer);
+        Future<RecordMetadata> record = kafkaProducer.send("data", "{\"site\" : \"baeldung\"}");
+        assertFalse(record.isDone());
+
+        //then
+        kafkaProducer.flush();
+        assertTrue(record.isDone());
+    }
+
+    @Test
+    void givenKeyValue_whenSend_thenReturnException() {
+
+        buildMockProducer(false);
+        //when
+        kafkaProducer = new KafkaProducer(mockProducer);
+        Future<RecordMetadata> record = kafkaProducer.send("site", "{\"site\" : \"baeldung\"}");
+        RuntimeException e = new RuntimeException();
+        mockProducer.errorNext(e);
+        //then
+        try {
+            record.get();
+        } catch (ExecutionException | InterruptedException ex) {
+            assertEquals(e, ex.getCause());
+        }
+        assertTrue(record.isDone());
+    }
+
+    @Test
+    void givenKeyValue_whenSendWithTxn_thenSendOnlyOnTxnCommit() {
+
+        buildMockProducer(true);
+        //when
+        kafkaProducer = new KafkaProducer(mockProducer);
+        kafkaProducer.initTransaction();
+        kafkaProducer.beginTransaction();
+        Future<RecordMetadata> record = kafkaProducer.send("data", "{\"site\" : \"baeldung\"}");
+
+        //then
+        assertTrue(mockProducer.history().isEmpty());
+        kafkaProducer.commitTransaction();
+        assertTrue(mockProducer.history().size() == 1);
+    }
+
+    @Test
+    void givenKeyValue_whenSendWithPartitioning_thenVerifyPartitionNumber() throws ExecutionException, InterruptedException {
+
+        PartitionInfo partitionInfo0 = new PartitionInfo(TOPIC_NAME, 0, null, null, null);
+        PartitionInfo partitionInfo1 = new PartitionInfo(TOPIC_NAME, 1, null, null, null);
+        List<PartitionInfo> list = new ArrayList<>();
+        list.add(partitionInfo0);
+        list.add(partitionInfo1);
+        Cluster cluster = new Cluster("kafkab", new ArrayList<Node>(), list, emptySet(), emptySet());
+        this.mockProducer = new MockProducer<>(cluster, true, new EvenOddPartitioner(), new StringSerializer(), new StringSerializer());
+        //when
+        kafkaProducer = new KafkaProducer(mockProducer);
+        Future<RecordMetadata> recordMetadataFuture = kafkaProducer.send("partition", "{\"site\" : \"baeldung\"}");
+
+        //then
+        assertTrue(recordMetadataFuture.get().partition() == 1);
+
+    }
+
+}