BarbelHisto in Spring Boot using event-driven persistence

The following example demonstrates how to use BarbelHisto in a Spring Boot application. There are two fundamental alternatives to integrate BarbelHisto into Spring Boot: using BarbelHisto as a helper class in your services, or you use BarbelHisto event listener persistence within Spring Boot services. This example demonstrates the event listener alternative.

The Spring Boot example application can be found here in the examples repository.

Customer Model

Here is the Customer POJO used in the subsequent examples.

public class Customer implements Bitemporal {

    @Id
    private String id;
    
    @DocumentId
    private String clientId;
    
    // version stamp
    private BitemporalStamp bitemporalStamp;
    
    private String firstName;
    private String lastName;
    private String street;
    private String city;
    private String postalcode;

    // constructor and accessors ...

}    

The @Id annotation is a spring annotation which uniquely identifies an object in the data source you use. We will use a MongoDB repository in this example. The @DocumentId is a BarbelHisto annotation to identify the functional identifier of the business object. A certain customer is uniquely identified by his corresponding clientId.

Notice that we use BarbelMode.BITEMPORAL in this setup, so the Customer implements the Bitemporal interface. The BitemporalStamp will contain the version data. When users of BarbelHisto use custom persistence it can be more convenient to use BarbelHisto in the BarbelMode.BITEMPORAL. No proxying magic will be applied to any objects. And objects are stored as they are, just with an additional BitemporalStamp. This mode is very explicit and straight forward.

Spring boot conversion classes

We need a converter for reading Customer objects previously stored by the event listeners.

public class CustomerReadConverter implements Converter<Document, Customer>{

    private Gson gson = BarbelHistoContext.getDefaultGson();
    @Override
    public Customer convert(Document source) {
        return gson.fromJson(source.toJson(), Customer.class);
    }

}

We demonstrate how to register these converters in Spring Boot later.

The CustomerRepository

In the example we're using a mongo repository like this one:

public interface CustomerRepository extends MongoRepository<Customer, String> {

    public List<Customer> findByLastName(String lastName);
    
    public List<Bitemporal> findByClientId(String clientId);
    
    public List<Bitemporal> findByClientIdAndBitemporalStampRecordTimeState(String clientId, BitemporalObjectState state);
    
}

The method findByClientId draws the complete version data for a given clientId. The findByClientIdAndBitemporalStampRecordTimeState draws active or inactive versions using the BitemporalStamp we've applied to the Customer object.

The CustomerService using a BarbelHisto instance

Here is the service implementation that uses BarbelHisto with event-driven persistence.

@Component
public class CustomerService {

    @Autowired
    private BarbelHisto<Customer> barbel;

    public void saveCustomer(Customer customer, LocalDate from, LocalDate until) {

        barbel.save(customer, from, until);

    }

}

The service autowires the barbel and uses it to store the data into the underlying MongoCollection.

The Spring boot configuration

Let's look at the Spring Boot configuration to put all the above stuff together.

@SpringBootApplication
public class BarbelHistoListenerIntegrationApplication extends MongoConfigurationSupport implements CommandLineRunner {

    @Autowired
    private CustomerService service;
    
    @Autowired
    private CustomerRepository repository;

    @Bean
    public BarbelHisto<Customer> barbel(MongoClient client) {
        SimpleMongoUpdateListener updateListener = SimpleMongoUpdateListener.create(
                client, "test", "customer", Customer.class,
                BarbelHistoContext.getDefaultGson());
        SimpleMongoLazyLoadingListener loadingListener = SimpleMongoLazyLoadingListener.create(
                client, "test", "customer", Customer.class,
                BarbelHistoContext.getDefaultGson(), true, true);
        MongoPessimisticLockingListener locking = MongoPessimisticLockingListener
                .create(client, "tsLockDb", "docLocks");
        return BarbelHistoBuilder.barbel().withMode(BarbelMode.BITEMPORAL).withSynchronousEventListener(updateListener)
                .withSynchronousEventListener(loadingListener).withSynchronousEventListener(locking).build();
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(BarbelHistoListenerIntegrationApplication.class, args);
    }
    
    @Override
    protected String getDatabaseName() {
        return "test";
    }

    @Override
    public MongoCustomConversions customConversions() {
        final List<Converter<?, ?>> converters = new ArrayList<Converter<?, ?>>();
        converters.add(new CustomerReadConverter());
        return new MongoCustomConversions(converters);
    }

    @Override
    public void run(String... args) throws Exception {

        Customer customer = new Customer("1234", "Alice", "Smith", "Some Street 10", "Houston", "77001");
        
        // save a couple of customers
        service.saveCustomer(customer, LocalDate.now(), EffectivePeriod.INFINITE);
        service.saveCustomer(customer, LocalDate.now().plusDays(10), EffectivePeriod.INFINITE);
        service.saveCustomer(customer, LocalDate.now().plusDays(20), EffectivePeriod.INFINITE);
        
        // validate the state of the journal
        Assert.isTrue(repository.findByClientIdAndBitemporalStampRecordTimeState("1234", BitemporalObjectState.ACTIVE).size() == 3, "must contain 3 active records");
        Assert.isTrue(repository.findByClientIdAndBitemporalStampRecordTimeState("1234", BitemporalObjectState.INACTIVE).size() == 2, "must contain 2 inactive records");

        service.saveCustomer(customer, LocalDate.now().minusDays(1), EffectivePeriod.INFINITE);
        
        // validate the state of the journal
        Assert.isTrue(repository.findByClientIdAndBitemporalStampRecordTimeState("1234", BitemporalObjectState.ACTIVE).size() == 1, "must contain 1 active records");
        Assert.isTrue(repository.findByClientIdAndBitemporalStampRecordTimeState("1234", BitemporalObjectState.INACTIVE).size() == 5, "must contain 5 inactive records");
        
        System.out.println(repository.findAll().toString());
    }
}

Notice that the run method performs some updates using the CustomerService just as demo here.