Error to serialize message when sending to kafka topic

Question

i need to test a message, which contains headers, so i need to use MessageBuilder, but I can not serialize.

I tried adding the serialization settings on the producer props but it did not work.

Can someone help me?

this error:

org.apache.kafka.common.errors.SerializationException: Can't convert value of class org.springframework.messaging.support.GenericMessage to class org.apache.kafka.common.serialization.StringSerializer specified in value.serializer

My test class:

public class TransactionMastercardAdapterTest extends AbstractTest{

@Autowired
private KafkaTemplate<String, Message<String>> template;

@ClassRule
public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1);

@BeforeClass
public static void setUp() {
    System.setProperty("spring.kafka.bootstrap-servers", embeddedKafka.getBrokersAsString());
    System.setProperty("spring.cloud.stream.kafka.binder.zkNodes", embeddedKafka.getZookeeperConnectionString());
}

@Test
public void sendTransactionCommandTest(){

    String payload = "{\"o2oTransactionId\" : \"" + UUID.randomUUID().toString().toUpperCase() + "\","
            + "\"cardId\" : \"11\","
            + "\"transactionId\" : \"20110405123456\","
            + "\"amount\" : 200.59,"
            + "\"partnerId\" : \"11\"}";

    Map<String, Object> props = KafkaTestUtils.producerProps(embeddedKafka);
    props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
    props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

    Producer<String, Message<String>> producer = new KafkaProducer<>(props);
    producer.send(new ProducerRecord<String, Message<String>> ("notification_topic", MessageBuilder.withPayload(payload)
            .setHeader("status", "RECEIVED")
            .setHeader("service", "MASTERCARD")
            .build()));

    Map<String, Object> configs = KafkaTestUtils.consumerProps("test1", "false", embeddedKafka);

    configs.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
    ConsumerFactory<byte[], byte[]> cf = new DefaultKafkaConsumerFactory<>(configs);

    Consumer<byte[], byte[]> consumer = cf.createConsumer();
    consumer.subscribe(Collections.singleton("transaction_topic"));
    ConsumerRecords<byte[], byte[]> records = consumer.poll(10_000);
    consumer.commitSync();

    assertThat(records.count()).isEqualTo(1);
}

}

Answer 1

I'd say the error is obvious:

Can't convert value of class org.springframework.messaging.support.GenericMessage to class org.apache.kafka.common.serialization.StringSerializer specified in value.serializer

Where your value is GenericMessage , but StringSerializer can work only with strings.

What you need is called JavaSerializer which does not exist, but not so difficult to write:

public class JavaSerializer implements Serializer<Object> {

    @Override
    public byte[] serialize(String topic, Object data) {
        try {
            ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
            ObjectOutputStream objectStream = new ObjectOutputStream(byteStream);
            objectStream.writeObject(data);
            objectStream.flush();
            objectStream.close();
            return byteStream.toByteArray();
        }
        catch (IOException e) {
            throw new IllegalStateException("Can't serialize object: " + data, e);
        }
    }

    @Override
    public void configure(Map<String, ?> configs, boolean isKey) {

    }

    @Override
    public void close() {

    }

}

And configure it for that value.serializer property.

Answer 2

private void configureProducer() {
Properties props = new Properties();
props.put("key.serializer",
        "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer",
        "org.apache.kafka.common.serialization.ByteArraySerializer");

producer = new KafkaProducer<String, String>(props);

}

This will do the job.

Answer 3

在我的情况下，我使用的是 spring cloud 并且没有在属性文件中添加以下属性

spring.cloud.stream.kafka.binder.configuration.value.serializer=org.apache.kafka.common.serialization.StringSerializer

Answer 4

This is what I used and it worked for me

Map<String, Object> configProps = new HashMap<>();
configProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, org.apache.kafka.common.serialization.StringSerializer.class);
configProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, org.springframework.kafka.support.serializer.JsonSerializer.class);

Answer 5

spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.IntegerSerializer spring.kafka.producer.value-serializer=org.apache.kafka.common.serialization.StringSerializer

Answer 6

使用@XmlRootElement注释 JSON 类