KafkaStreams serde exception

Question

i am playing with Kafka and streams technology; i have created a custom serializer and deserializer for the KStream that i will use to receive messages from a given topic.

Answer 1

To complete the Matthias answer I've just coded a simple example of how to create a custom Serde (Serializer / Deserializer) within a Kafka Stream App. It's is available to clone and try in: https://github.com/Davidcorral94/Kafka-Streams-Custom-Seder

First I create two classes, one for the Serializer and another for the Deserializer. In this case I use Gson library to perform the serialization/deserialization.

Serializer

public class PersonSerializer implements Closeable, AutoCloseable, Serializer {

    private static final Charset CHARSET = Charset.forName("UTF-8");
    static private Gson gson = new Gson();

    @Override
    public void configure(Map map, boolean b) {
    }

    @Override
    public byte[] serialize(String s, Person person) {
        // Transform the Person object to String
        String line = gson.toJson(person);
        // Return the bytes from the String 'line'
        return line.getBytes(CHARSET);
    }

    @Override
    public void close() {

    }
}

Deserializer

public class PersonDeserializer implements Closeable, AutoCloseable, Deserializer {

    private static final Charset CHARSET = Charset.forName("UTF-8");
    static private Gson gson = new Gson();

    @Override
    public void configure(Map map, boolean b) {
    }

    @Override
    public Person deserialize(String topic, byte[] bytes) {
        try {
            // Transform the bytes to String
            String person = new String(bytes, CHARSET);
            // Return the Person object created from the String 'person'
            return gson.fromJson(person, Person.class);
        } catch (Exception e) {
            throw new IllegalArgumentException("Error reading bytes", e);
        }
    }

    @Override
    public void close() {

    }
}

Then, I wrap both of them into a Serde to be able to use it into my Kafka Stream App.

Serde

public class PersonSerde implements Serde {
    private PersonSerializer serializer = new PersonSerializer();
    private PersonDeserializer deserializer = new PersonDeserializer();

    @Override
    public void configure(Map configs, boolean isKey) {
        serializer.configure(configs, isKey);
        deserializer.configure(configs, isKey);
    }

    @Override
    public void close() {
        serializer.close();
        deserializer.close();
    }

    @Override
    public Serializer serializer() {
        return serializer;
    }

    @Override
    public Deserializer deserializer() {
        return deserializer;
    }
}

Finally, you are able to use this Serde class into your Kafka Stream App with the next line:

props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, PersonSerde.class);

This is actually working with the latest Kafka version available at this moment which is 1.0.0!