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KafkaException: class is not an instance of org.apache.kafka.common.serialization.Deserializer

I want to implement Kafka producer which sends and receives Java Serialized Objects. I tried this:

Producer:

@Configuration
public class KafkaProducerConfig {

@Value(value = "${kafka.bootstrapAddress}")
private String bootstrapAddress;

@Bean
public ProducerFactory<String, SaleRequestFactory> saleRequestFactoryProducerFactory() {
    Map<String, Object> configProps = new HashMap<>();
    configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
    configProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, SaleRequestFactory.class);
    configProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, SaleRequestFactory.class);
    return new DefaultKafkaProducerFactory<>(configProps);
}

@Bean
public ProducerFactory<String, String> producerFactory() {
    Map<String, Object> configProps = new HashMap<>();
    configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
    /*
        Serialization configuration
     */
    return new DefaultKafkaProducerFactory<>(configProps);
}


@Bean
public KafkaTemplate<String, SaleRequestFactory> saleRequestFactoryKafkaTemplate() {
    return new KafkaTemplate<>(saleRequestFactoryProducerFactory());
}

@Bean
public KafkaTemplate<String, String> kafkaTemplate() {
    return new KafkaTemplate<>(producerFactory());
}

}

Send object:

@Autowired
private KafkaTemplate<String, SaleRequestFactory> saleRequestFactoryKafkaTemplate;

private static String topic = "tp-sale";

private void perform(){

    SaleRequestFactory obj = new SaleRequestFactory();
    obj.setId(100);

    ListenableFuture<SendResult<String, SaleRequestFactory>> send = saleRequestFactoryKafkaTemplate.send(topic, obj);
}

Consumer:

@EnableKafka
@Configuration
public class KafkaConsumerConfig {

    @Value(value = "${kafka.bootstrapAddress}")
    private String bootstrapAddress;

    private String groupId = "test";

    @Bean
    public ConsumerFactory<String, SaleResponseFactory> consumerFactory() {
        Map<String, Object> props = new HashMap<>();
        props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
        props.put(ConsumerConfig.GROUP_ID_CONFIG, groupId);
        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, SaleResponseFactory.class);
        return new DefaultKafkaConsumerFactory<>(props);
    }

    @Bean
    public ConcurrentKafkaListenerContainerFactory<String, SaleResponseFactory> kafkaListenerContainerFactory() {
        ConcurrentKafkaListenerContainerFactory<String, SaleResponseFactory> factory =
                new ConcurrentKafkaListenerContainerFactory<>();
        factory.setConsumerFactory(consumerFactory());
        return factory;
    }
}

// Receive Object

    @KafkaListener(topics = "tp-sale")
public SaleResponseFactory transactionElavonAuthorizeProcess(@Payload SaleRequestFactory tf, @Headers MessageHeaders headers) throws Exception {

    System.out.println(tf.getId());

    SaleResponseFactory resObj = new SaleResponseFactory();
    resObj.setUnique_id("123123");

    return resObj;
}

When I deploy the Producer I get error during deployment:

Caused by: org.apache.kafka.common.KafkaException: class org.engine.plugin.transactions.factory.SaleResponseFactory is not an instance of org.apache.kafka.common.serialization.Deserializer

Custom object

import org.apache.kafka.common.serialization.Serializer;

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@Builder(toBuilder = true)
public class SaleRequestFactory implements Serializable, Serializer {

    private static final long serialVersionUID = 1744050117179344127L;
    
    private int id;

    @Override
    public byte[] serialize(String s, Object o) {
        return new byte[0];
    }
}

import org.apache.kafka.common.serialization.Deserializer; @Getter @Setter @NoArgsConstructor @AllArgsConstructor @Builder(toBuilder = true) public class SaleResponseFactory implements Serializable, Deserializer { private static final long serialVersionUID = 1744050117179344127L; private String unique_id; @Override public Object deserialize(String s, byte[] bytes) { return null; } }

Do you know how I can fix this issue?

EDIT: I tried this:

Producer:

@Configuration
public class KafkaProducerConfig {

@Value(value = "${kafka.bootstrapAddress}")
private String bootstrapAddress;

@Bean
public ProducerFactory<String, SaleRequestFactory> saleRequestFactoryProducerFactory() {
    Map<String, Object> configProps = new HashMap<>();
    configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
    configProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
    configProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, SaleRequestFactorySerializer.class);
    return new DefaultKafkaProducerFactory<>(configProps);
}

@Bean
public ProducerFactory<String, String> producerFactory() {
    Map<String, Object> configProps = new HashMap<>();
    configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
    return new DefaultKafkaProducerFactory<>(configProps);
}


@Bean
public KafkaTemplate<String, SaleRequestFactory> saleRequestFactoryKafkaTemplate() {
    return new KafkaTemplate<>(saleRequestFactoryProducerFactory());
}

@Bean
public KafkaTemplate<String, String> kafkaTemplate() {
    return new KafkaTemplate<>(producerFactory());
}

}

Send object:

@Autowired
private KafkaTemplate<String, SaleRequestFactory> saleRequestFactoryKafkaTemplate;

private static String topic = "tp-sale";

private void perform(){

    SaleRequestFactory obj = new SaleRequestFactory();
    obj.setId(100);

    ListenableFuture<SendResult<String, SaleRequestFactory>> send = saleRequestFactoryKafkaTemplate.send(topic, obj);
}

Consumer:

@EnableKafka
@Configuration
public class KafkaConsumerConfig {

    @Value(value = "${kafka.bootstrapAddress}")
    private String bootstrapAddress;

    private String groupId = "test";

    @Bean
    public ConsumerFactory<String, SaleResponseFactory> consumerFactory() {
        Map<String, Object> props = new HashMap<>();
        props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
        props.put(ConsumerConfig.GROUP_ID_CONFIG, groupId);
        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, SaleResponseFactoryDeserializer.class);
        return new DefaultKafkaConsumerFactory<>(props);
    }

    @Bean
    public ConcurrentKafkaListenerContainerFactory<String, SaleResponseFactory> kafkaListenerContainerFactory() {
        ConcurrentKafkaListenerContainerFactory<String, SaleResponseFactory> factory =
                new ConcurrentKafkaListenerContainerFactory<>();
        factory.setConsumerFactory(consumerFactory());
        return factory;
    }
}

// Receive Object

    @KafkaListener(topics = "tp-sale")
public SaleResponseFactory transactionElavonAuthorizeProcess(@Payload SaleRequestFactory tf, @Headers MessageHeaders headers) throws Exception {

    System.out.println(tf.getId());

    SaleResponseFactory resObj = new SaleResponseFactory();
    resObj.setUnique_id("123123");

    return resObj;
}

Custom objects

    @Getter
    @Setter
    @NoArgsConstructor
    @AllArgsConstructor
    @Builder(toBuilder = true)
    public class SaleRequestFactory implements Serializable{
    
        private static final long serialVersionUID = 1744050117179344127L;
        
        private int id;
    }

public class SaleRequestFactorySerializer implements Serializable, Serializer<SaleRequestFactory> {

    @Override
    public byte[] serialize(String topic, SaleRequestFactory data) {
        // convert data to byte[]
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        try
        {
            ObjectOutputStream outputStream = new ObjectOutputStream(out);
            outputStream.writeObject(data);
            out.close();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }

        return out.toByteArray();
    }
}


    @Getter
    @Setter
    @NoArgsConstructor
    @AllArgsConstructor
    @Builder(toBuilder = true)
    public class SaleResponseFactory implements Serializable{
    
        private static final long serialVersionUID = 1744050117179344127L;
    
        private String unique_id;
    }

public class SaleResponseFactoryDeserializer implements Serializable, Deserializer<SaleResponseFactory> {

    @Override
    public SaleResponseFactory deserialize(String topic, byte[] data) {
        // convert data to SaleResponseFactory
        SaleResponseFactory saleResponseFactory = null;
        try
        {
            ByteArrayInputStream bis = new ByteArrayInputStream(data);
            ObjectInputStream in = new ObjectInputStream(bis);
            saleResponseFactory = (SaleResponseFactory) in.readObject();
            in.close();
        }
        catch (IOException | ClassNotFoundException e)
        {
            e.printStackTrace();
        }
        return saleResponseFactory;
    }
}

When I try to send message I get error:

Caused by: org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition tp-sale-0 at offset 0. If needed, please seek past the record to continue consumption.
Caused by: java.lang.ClassCastException: null
21:27:51.152 [org.springframework.kafka.KafkaListenerEndpointContainer#0-0-C-1] DEBUG KafkaMessageListenerContainer$ListenerConsumer[debug:296] - Commit list: {}
21:27:51.153 [org.springframework.kafka.KafkaListenerEndpointContainer#0-0-C-1] ERROR KafkaMessageListenerContainer$ListenerConsumer[error:149] - Consumer exception
java.lang.IllegalStateException: This error handler cannot process 'SerializationException's directly; please consider configuring an 'ErrorHandlingDeserializer' in the value and/or key deserializer
        at org.springframework.kafka.listener.SeekUtils.seekOrRecover(SeekUtils.java:145)
        at org.springframework.kafka.listener.SeekToCurrentErrorHandler.handle(SeekToCurrentErrorHandler.java:103)
        at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.handleConsumerException(KafkaMessageListenerContainer.java:1265)
        at org.springframework.kafka.listener.KafkaMessageListenerContainer$ListenerConsumer.run(KafkaMessageListenerContainer.java:1022)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
        at java.base/java.lang.Thread.run(Thread.java:835)
Caused by: org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition tp-sale-0 at offset 0. If needed, please seek past the record to continue consumption.
Caused by: java.lang.ClassCastException: null

Do you know how I can fix this issue?

EDIT: I managed to implement these improvements:

Producer:

@Configuration
public class KafkaProducerConfig {

@Value(value = "${kafka.bootstrapAddress}")
private String bootstrapAddress;

@Bean
public ProducerFactory<String, SaleRequestFactory> saleRequestFactoryProducerFactory() {
    Map<String, Object> configProps = new HashMap<>();
    configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
    configProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
    configProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, SaleRequestFactorySerializer.class);
    return new DefaultKafkaProducerFactory<>(configProps);
}

@Bean
public ProducerFactory<String, String> producerFactory() {
    Map<String, Object> configProps = new HashMap<>();
    configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
    return new DefaultKafkaProducerFactory<>(configProps);
}


@Bean
public KafkaTemplate<String, SaleRequestFactory> saleRequestFactoryKafkaTemplate() {
    return new KafkaTemplate<>(saleRequestFactoryProducerFactory());
}

@Bean
public KafkaTemplate<String, String> kafkaTemplate() {
    return new KafkaTemplate<>(producerFactory());
}

}

Send object:

@Autowired
private KafkaTemplate<String, SaleRequestFactory> saleRequestFactoryKafkaTemplate;

private static String topic = "tp-sale";

private void perform(){

    SaleRequestFactory obj = new SaleRequestFactory();
    obj.setId(100);

    ListenableFuture<SendResult<String, SaleRequestFactory>> send = saleRequestFactoryKafkaTemplate.send(topic, obj);
}

Consumer:

@EnableKafka
@Configuration
public class KafkaConsumerConfig {

    @Value(value = "${kafka.bootstrapAddress}")
    private String bootstrapAddress;

    private String groupId = "test";

    @Bean
    public ConsumerFactory<String, SaleResponseFactory> consumerFactory() {
        Map<String, Object> props = new HashMap<>();
        props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
        props.put(ConsumerConfig.GROUP_ID_CONFIG, groupId);
        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, SaleResponseFactoryDeserializer.class);
        return new DefaultKafkaConsumerFactory<>(props);
    }

    @Bean
    public ConcurrentKafkaListenerContainerFactory<String, SaleResponseFactory> kafkaListenerContainerFactory() {
        ConcurrentKafkaListenerContainerFactory<String, SaleResponseFactory> factory =
                new ConcurrentKafkaListenerContainerFactory<>();
        factory.setConsumerFactory(consumerFactory());
        return factory;
    }
}

Receive Object

    @KafkaListener(topics = "tp-sale")
public SaleResponseFactory transactionElavonAuthorizeProcess(@Payload SaleRequestFactory tf, @Headers MessageHeaders headers) throws Exception {

    System.out.println(tf.getId());

    SaleResponseFactory resObj = new SaleResponseFactory();
    resObj.setUnique_id("123123");

    return resObj;
}

Custom objects

    @Getter
    @Setter
    @NoArgsConstructor
    @AllArgsConstructor
    @Builder(toBuilder = true)
    public class SaleRequestFactory implements Serializable{
    
        private static final long serialVersionUID = 1744050117179344127L;
        
        private int id;
    }

public class SaleRequestFactorySerializer implements Serializable, Serializer<SaleRequestFactory> {

    @Override
    public byte[] serialize(String topic, SaleRequestFactory data) {
        // convert data to byte[]
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        try
        {
            ObjectOutputStream outputStream = new ObjectOutputStream(out);
            outputStream.writeObject(data);
            out.close();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }

        return out.toByteArray();
    }
}


    @Getter
    @Setter
    @NoArgsConstructor
    @AllArgsConstructor
    @Builder(toBuilder = true)
    public class SaleResponseFactory implements Serializable{
    
        private static final long serialVersionUID = 1744050117179344127L;
    
        private String unique_id;
    }

public class SaleResponseFactoryDeserializer implements Serializable, Deserializer<SaleResponseFactory> {

    @Override
    public SaleResponseFactory deserialize(String topic, byte[] data) {
        // convert data to SaleResponseFactory
        SaleResponseFactory saleResponseFactory = null;
        try
        {
            ByteArrayInputStream bis = new ByteArrayInputStream(data);
            ObjectInputStream in = new ObjectInputStream(bis);
            saleResponseFactory = (SaleResponseFactory) in.readObject();
            in.close();
        }
        catch (IOException | ClassNotFoundException e)
        {
            e.printStackTrace();
        }
        return saleResponseFactory;
    }
}

When I send some message I get error:

13:03:53.675 [org.springframework.kafka.KafkaListenerEndpointContainer#0-0-C-1] DEBUG RecordMessagingMessageListenerAdapter[debug:296] - Listener method returned result [org.factory.SaleResponseFactory@69c400ab] - generating response message for it
13:03:53.675 [org.springframework.kafka.KafkaListenerEndpointContainer#0-0-C-1] DEBUG RecordMessagingMessageListenerAdapter[debug:296] - No replyTopic to handle the reply: org.factory.SaleResponseFactory@69c400ab

Do you know how I can solve this issue?

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Answer

You are using different type to cast the object than what it was serialize with. Not sure why you need to do that. You can update your deserialize to something like below.

public class SaleRequestFactoryDeserializer implements Serializable, Deserializer<SaleRequestFactory> {

     @Override
     public SaleRequestFactory deserialize(String topic, byte[] data) {
      ...
        saleRequestFactory = (SaleRequestFactory) in.readObject();

    }
}

java.lang.ClassCastException: null

This also means your serialization didn’t work as expected. Make sure you have valid payload before you try to cast.

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