Event Driven Architecture - Event Versioning

AccountOpenedEventHandler.java

public class AccountOpenedEvent {
    private String accountId;
    private String customerDetails;
    private String accountOpeningDetails;
    private int version; // Add a version field
}

@Component
public class AccountOpenedEventHandler {
    private List<AccountOpenedEventProcessor> processors;

    public AccountOpenedEventHandler() {
        processors = new ArrayList<>();
        processors.add(new AccountOpenedEventProcessorV1());
        processors.add(new AccountOpenedEventProcessorV2());
    }

    @StreamListener(target = "accountOpenedInput")
    public void handleAccountOpenedEvent(AccountOpenedEvent event) {
        for (AccountOpenedEventProcessor processor : processors) {
            if (processor.supports(event)) {
                processor.process(event);
                return;
            }
        }

        handleUnsupportedVersion(event);
    }

    public void handleUnsupportedVersion(AccountOpenedEvent event) {
        // Handle unsupported version or fallback logic
    }
}

interface AccountOpenedEventProcessor {
    boolean supports(AccountOpenedEvent event);
    void process(AccountOpenedEvent event);
}

class AccountOpenedEventProcessorV1 implements AccountOpenedEventProcessor {
    @Override
    public boolean supports(AccountOpenedEvent event) {
        return event.getVersion() == 1;
    }

    @Override
    public void process(AccountOpenedEvent event) {
        // Handle version 1 logic for AccountOpened event
    }
}

class AccountOpenedEventProcessorV2 implements AccountOpenedEventProcessor {
    @Override
    public boolean supports(AccountOpenedEvent event) {
        return event.getVersion() == 2;
    }

    @Override
    public void process(AccountOpenedEvent event) {
        // Handle version 2 logic for AccountOpened event
    }
}