Implement Agents

• For each agent there will be an abstract class Agent Base generated in the SDK

• The Agent Base provides access to the repository, the entity builder, the event builder and the event producer

• The Agent Base contains one abstract method named onMessage

• The onMessage method needs to be implemented in the generated implementation file for the agent

• The default behavior can be changed by overriding the method onMessage( ConsumerRecord consumerRecord, MessageHeaders headers) in the agent directly. There is also the possibility to access the initial ConsumerRecord.

• The agent implementation file onMessage is automatically triggered when the Kafka event that the agent is modelled against is received.

• Agent onMessage method will receive Payload Entity as first parameter (if event that the agent receives is modelled with a payload).

• Agent onMessage method will also receive MessageHeaders as a parameter which is a key-value map that contains Kafka message headers.

Example of Balance service implementation file.

package de.knowis.cards.operations.domain.cc.agent;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
import org.springframework.messaging.MessageHeaders;

import de.knowis.cards.operations.sdk.domain.cc.agent.CreditCardCreatedAgentBase;
import de.knowis.cards.operations.domain.facade.DomainEntityBuilder;
import de.knowis.cards.operations.domain.facade.DomainEventBuilder;
import de.knowis.cards.operations.sdk.domain.facade.Repository;
import de.knowis.cards.operations.sdk.domain.service.EventProducerService;
import de.knowis.cards.operations.sdk.domain.cc.entity.CreditCard;
import de.knowis.cards.operations.sdk.domain.cc.entity.Card;

@Service
public class CreditCardCreatedAgent extends CreditCardCreatedAgentBase {

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

  // Declare Card Command 
  private final CardCommandBase cardCommand;

  // Adjust your generated agent constructor to inject CardCommandBase so it can be used in agent logic
  public CreditCardCreatedAgent(DomainEntityBuilder entityBuilder, DomainEventBuilder eventBuilder, EventProducerService eventProducer, Repository repo, CardCommandBase cardCommand) {
    super(entityBuilder,eventBuilder, eventProducer,repo);
    this.cardCommand = cardCommand;
  }

  
  @Override
  public void onMessage(CreditCard creditCard, MessageHeaders headers) {

    log.info("Agent CreditCardCreatedAgent received event cc:CreditCardCreated");

    // Get root entity through repository
    Card card = this.repo.getCc().getCards().findById(creditCard.getId());

    // Call activateCard instance command to activate Card 
    // (this will call implemented logic for activate card command)
    cardCommand.activateCard(card);
  }
}

Example to override the default behavior of onMessage method (Java Spring Boot Stack 2.0 only) in Balance service implementation file.

package de.knowis.cards.operations.domain.cc.agent;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
import org.springframework.messaging.MessageHeaders;

import de.knowis.cards.operations.sdk.domain.cc.agent.CreditCardCreatedAgentBase;
import de.knowis.cards.operations.domain.facade.DomainEntityBuilder;
import de.knowis.cards.operations.domain.facade.DomainEventBuilder;
import de.knowis.cards.operations.sdk.domain.facade.Repository;
import de.knowis.cards.operations.sdk.domain.service.EventProducerService;
import de.knowis.cards.operations.sdk.domain.cc.entity.CreditCard;
import de.knowis.cards.operations.sdk.domain.cc.entity.Card;

@Service
public class CreditCardCreatedAgent extends CreditCardCreatedAgentBase {

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

  // Declare Card Command 
  private final CardCommandBase cardCommand;

  // Adjust your generated agent constructor to inject CardCommandBase so it can be used in agent logic
  public CreditCardCreatedAgent(DomainEntityBuilder entityBuilder, DomainEventBuilder eventBuilder, EventProducerService eventProducer, Repository repo, CardCommandBase cardCommand) {
    super(entityBuilder,eventBuilder, eventProducer,repo);
    this.cardCommand = cardCommand;
  }

  @Override
  public void onMessage(CreditCard creditCard, MessageHeaders headers) {
    log.info("Agent CreditCardCreatedAgent received event cc:CreditCardCreated");
  }

  @Override
  // optional could be implemented in case there is a need for ConsumerRecord
  // Gives the opportunity to access message key, headers and timestamp from ConsumerRecord
  // only available for Domain Services (Java) based on Java Spring Boot Stack 2.0
  public void onMessage(ConsumerRecord<?, ?> consumerRecord, MessageHeaders headers) {

    // get message key from consumerRecord
    Object messageKey = consumerRecord.key();

    // get message header
    String customerHeader = new String(consumerRecord.headers().lastHeader("customerHeaderName").value());

    // get message Timestamp from consumerRecord
    long messageTimeStamp = consumerRecord.timestamp();

    log.info("Agent CreditCardCreatedAgent received event cc:CreditCardCreated");

    // Get root entity through repository
    Card card = this.repo.getCc().getCards().findById(creditCard.getId());

    // Call activateCard instance command to activate Card 
    // (this will call implemented logic for activate card command)
    cardCommand.activateCard(card);
  }
}