Headers

Springwolf provides different ways to document headers. The header is mapped to an AsyncAPI schemaObject.

Auto-detection

Besides the payload, Springwolf detects the Spring @Header annotation within the method signature:

@KafkaListener(topics = "example-topic")
public void receiveExamplePayload(
        @Payload ExamplePayloadDto payload, // @Payload is required for multiple parameters
        @Header(KafkaHeaders.RECEIVED_KEY) String key,
        @Header(KafkaHeaders.OFFSET) Integer offset) {
    // process
}

Using @AsyncOperation.Headers

Again, the annotation property headers of @AsyncOperation allows to overwrite the headers, as shown below:

@AsyncPublisher(operation = @AsyncOperation(
        channelName = "example-producer-topic",
        headers = @AsyncOperation.Headers( // Optional
                schemaName = "SpringKafkaDefaultHeaders",
                values = {
                        @AsyncOperation.Headers.Header(
                                name = DEFAULT_CLASSID_FIELD_NAME,
                                description = "Spring Type Id Header",
                                value = "io.github.springwolf.example.dtos.ExamplePayloadDto"
                        ),
                        // demonstrating https://cloudevents.io
                        @AsyncOperation.Headers.Header(
                                name = AsyncHeadersCloudEventConstants.TYPE,
                                description = AsyncHeadersCloudEventConstants.TYPE_DESC,
                                value = "ExamplePayloadDto.v1")
                        // ...
                }
        )
))
public void sendMessage(ExamplePayloadDto msg) {
    // process
}