Message Headers

The AMPS binder defines a set of message headers for conveying AMPS-specific metadata. These headers are available on consumed messages and can be set on outgoing messages.

All header constants are defined in the AmpsMessageHeaders class.

Standard Headers

These headers are automatically populated on consumed messages:

Header Key	Constant	Type	Direction	Description
ampsTopic	AmpsMessageHeaders.TOPIC	String	Inbound	The AMPS topic the message was received from
ampsCorrelationId	AmpsMessageHeaders.CORRELATION_ID	String	Both	The correlation ID for this message. An arbitrary string that can be used for application purposes. It is not interpreted by AMPS. Must only contain valid Base64 characters.
ampsBookmark	AmpsMessageHeaders.BOOKMARK	String	Inbound	The AMPS Bookmark for this message — an identifier assigned by AMPS to locate a message in the transaction log
ampsTimestamp	AmpsMessageHeaders.TIMESTAMP	String	Inbound	The timestamp for this message, an ISO-8601 formatted string set by AMPS at the time it processes the message (when withTimestamp=true)

Example: Reading Headers

@Bean
public Consumer<Message<byte[]>> consume() {
    return message -> {
        String topic = message.getHeaders().get("ampsTopic", String.class);
        String bookmark = message.getHeaders().get("ampsBookmark", String.class);
        String timestamp = message.getHeaders().get("ampsTimestamp", String.class);

        System.out.println("Topic: " + topic);
        System.out.println("Bookmark: " + bookmark);
        System.out.println("Timestamp: " + timestamp);
    };
}

Header Encoding Headers

These headers control the AMPS header converter, which encodes Spring message headers into the AMPS correlation ID:

Header Key	Constant	Type	Direction	Description
ampsMessageClass	AmpsMessageHeaders.MESSAGE_CLASS	String	Both	Message class name for header encoding
ampsMessageVersion	AmpsMessageHeaders.MESSAGE_VERSION	String	Both	Message class version
ampsMessageContentType	AmpsMessageHeaders.MESSAGE_CONTENT_TYPE	String	Both	Content type of the message
ampsMessageHeaderParams	AmpsMessageHeaders.MESSAGE_HEADER_PARAMS	Map<String, String>	Both	Map of additional key-value parameters
ampsPublishHeader	AmpsMessageHeaders.PUBLISH_AMPS_HEADER	Boolean	Outbound	Set to true to include AMPS header on this specific message

AMPS Header Encoding

When publishAmpsHeader is enabled (globally or per-message), the AmpsHeaderConverter encodes the following headers into the AMPS correlation ID:

1. ampsMessageContentType → contentType field
2. ampsMessageClass → messageClass field
3. ampsMessageVersion → messageVersion field
4. ampsMessageHeaderParams → additional fields from the map

The default encoding is Base64(JSON). For example:

{
  "contentType": "application/json",
  "messageClass": "Order",
  "messageVersion": "1.0",
  "traceId": "abc123",
  "spanId": "def456"
}

Is encoded as:

eyJjb250ZW50VHlwZSI6ImFwcGxpY2F0aW9uL2pzb24iLCJtZXNzYWdlQ2xhc3MiOiJPcmRlciIsIm1lc3NhZ2VWZXJzaW9uIjoiMS4wIiwidHJhY2VJZCI6ImFiYzEyMyIsInNwYW5JZCI6ImRlZjQ1NiJ9

On the consumer side, the correlation ID is decoded back into the individual headers.

Example: Publishing with Custom Headers

@Bean
public Function<String, Message<String>> process() {
    return input -> {
        Map<String, String> params = new HashMap<>();
        params.put("source", "order-service");
        params.put("region", "us-east");

        return MessageBuilder.withPayload(input)
            .setHeader(AmpsMessageHeaders.PUBLISH_AMPS_HEADER, true)
            .setHeader(AmpsMessageHeaders.MESSAGE_CLASS, "Order")
            .setHeader(AmpsMessageHeaders.MESSAGE_VERSION, "2.0")
            .setHeader(AmpsMessageHeaders.MESSAGE_CONTENT_TYPE, "application/json")
            .setHeader(AmpsMessageHeaders.MESSAGE_HEADER_PARAMS, params)
            .build();
    };
}