Message Formats

The library auto-resolves codecs for all built-in types at registration time — no manual override needed for most consumers:

Type	Auto-resolved codec
Plain POJO (Jackson)	JsonMessageCodec
String	StringMessageCodec
Avro SpecificRecord	AvroMessageCodec
Protobuf Message	ProtoMessageCodec

This applies symmetrically to both keys and values. For example, a consumer with <ShipmentKey, ShipmentEvent> (both POJOs) needs no codec overrides — the library detects both types and creates JsonMessageCodec instances automatically.

Explicit codec overrides

You can still override getKeyCodec() or getValueCodec() if needed (e.g. for custom formats). Explicit codecs take precedence over auto-resolution.

Avro

JavaKotlin

@Override
public MessageCodec<OrderEvent> getValueCodec() {
    return new AvroMessageCodec<>(OrderEvent.getClassSchema());
}

override fun getValueCodec(): MessageCodec<OrderEvent> =
    AvroMessageCodec(OrderEvent.getClassSchema())

Requires org.apache.avro:avro on the classpath (declared as provided by the library).

Protobuf

JavaKotlin

@Override
public MessageCodec<OrderEvent> getValueCodec() {
    return new ProtoMessageCodec<>(OrderEvent.getDefaultInstance());
}

override fun getValueCodec(): MessageCodec<OrderEvent> =
    ProtoMessageCodec(OrderEvent.getDefaultInstance())

Requires com.google.protobuf:protobuf-java and com.google.protobuf:protobuf-java-util on the classpath (both declared as provided).

Custom formats

Implement MessageCodec<T> directly for any format:

JavaKotlin

public class ThriftMessageCodec<T> implements MessageCodec<T> {

    @Override
    public String toJson(T value) {
        // serialize your value to JSON string
    }

    @Override
    public T fromJson(String json) {
        // deserialize JSON string to your value type
    }
}

class ThriftMessageCodec<T> : MessageCodec<T> {

    override fun toJson(value: T): String {
        // serialize your value to JSON string
    }

    override fun fromJson(json: String): T {
        // deserialize JSON string to your value type
    }
}

Then declare it on your consumer:

JavaKotlin

@Override
public MessageCodec<OrderEvent> getValueCodec() {
    return new ThriftMessageCodec<>();
}

override fun getValueCodec(): MessageCodec<OrderEvent> = ThriftMessageCodec()

Key codec overrides

Keys are auto-resolved just like values. Override getKeyCodec() only when you need a custom codec:

Protobuf keyCustom key

JavaKotlin

@Override
public MessageCodec<OrderKey> getKeyCodec() {
    return new ProtoMessageCodec<>(OrderKey.getDefaultInstance());
}

override fun getKeyCodec(): MessageCodec<OrderKey> =
    ProtoMessageCodec(OrderKey.getDefaultInstance())

JavaKotlin

@Override
public MessageCodec<MyKey> getKeyCodec() {
    return new MessageCodec<>() {
        @Override public String toJson(MyKey value) { /* serialize to JSON */ }
        @Override public MyKey fromJson(String json) { /* deserialize from JSON */ }
    };
}

override fun getKeyCodec(): MessageCodec<MyKey> = object : MessageCodec<MyKey> {
    override fun toJson(value: MyKey): String { /* serialize to JSON */ }
    override fun fromJson(json: String): MyKey { /* deserialize from JSON */ }
}