Publish Events

The generated SDK provides Builders for Events which can be easily used to construct events. It allows to set the payload of the event using the setPayload method. Depending on what has been defined as payload, it allows to use a schema from the schema registry for defining a payload or another entity (deprecated, see Events 1.0).

// Importing overall Event Builder
import de.knowis.cards.sdk.domain.facade.DomainEventBuilder;

// Declare and Inject Domain Event Builder
@Autowired
private DomainEventBuilder eventBuilder;

// Create a new instance of the event that should be published
CardCreatedEvent event = this.eventBuilder.getCc().getCardCreatedEvent().build();

// Create the payload for the event based on a schema and set it
SuccessSchema payloadSchema = new SuccessSchema();
payloadSchema.successful(true);
event.setPayload(payloadSchema);

/**
* Event 1.0 with entity payload
* @deprecated use schemas from the schema registry instead
*/
SuccessEventPayload payloadEntity = entityBuilder.getCc().successEventPayload().build();
event.setPayload(payloadEntity);

The autogenerated EventProducerService allows to easily publish business events to Kafka topics. The topic which is used is the one, that has been defined for the event during modelling. When using it, the connection to the Kafka will be automatically set up and does not require further code.

When publishing the event, it is possible to set custom headers and a custom message key (optional).

// Declare Event Producer Service
@Autowired
private EventProducerService eventProdcuer;

// Create business event
SuccessEvent event = eventBuilder.getCc().successEvent().build();

// set event payload
// ...

// Publish business event
eventProducer.publish(event);

// Alternative 1: publish the event with custom messageKey
eventProducer.publish(event, "customMessageKey");

// Alternative 2: publish the event with  messageHeaders
HashMap<String, Object> map = new HashMap();
map.put("headerKey", "headerValue");
MessageHeaders headers = new MessageHeaders(map);
eventProducer.publish(event, headers);

// Alternative 3: publish the event with messageKey and messageHeaders
eventProducer.publish(event, "customMessageKey", headers);

Implementation example for publishing events assigned to command, service or agent:

//... imports
import myproj.sdk.domain.schemas.SchemaGroup.BalanceCheckedSchema;

@Service
public class CardCommand extends CardCommandBase {

  private static Logger log = LoggerFactory.getLogger(CardCommand.class);

  @Override
  public Card createCreditCard(CreditCard creditCard) throws CreditCardCreationError {
    log.info("CardCommands.createCreditCard()");
    // ... some command implementation

    // Publish an event, using a schema from the schema registry as payload
    BalanceCheckedEvent schemaEvent = this.eventBuilder.getCc().getBalanceCheckedEvent().build();

    // Create the payload for the event
    BalanceCheckedSchema schema = new BalanceCheckedSchema();
    schema.setProperty1('value');
    schemaEvent.setPayload(schema);

    // create custom headers
    HashMap<String, Object> map = new HashMap();
    map.put("headerKey", "headerValue");
    MessageHeaders headers = new MessageHeaders(map);

    // publish the event with messageKey and messageHeaders
    this.publishBalanceCheckedEvent(schemaEvent, "customMessageKey", headers);

    // ... further command implementation
  }
}