Setting up MongoDB in 5 minutes

If you want to make MongoDB work with BarbelHisto you need two maven dependencies to get started.

The mongo package is tested MongoDB Java Driver 3.6.4

<dependency>
    <groupId>org.mongodb</groupId>
    <artifactId>mongodb-driver</artifactId>
    <version>3.6.4</version>
</dependency>

Develop a Pojo, like this one:

public class Client {

    @DocumentId
    private String clientId;
    private String title;
    private String name;
    private String firstname;
    private String address;
    private String email;
    private LocalDate dateOfBirth;

}

Notice that we use the @DocumentId annotation to tell BarbelHisto that the clientId uniquely identifies the client and this should be the document id. BarbelHisto will maintain document journals for each document id.

Now, create an instance of BarbelHisto with mongo collection shadows like so:

MongoClient mongoClient = SimpleMongoListenerClient.create("mongodb://localhost:12345").getMongoClient();
// update listener
SimpleMongoUpdateListener updateListener = SimpleMongoUpdateListener.create(mongoClient, "testDb", "testCol", Client.class, BarbelHistoContext.getDefaultGson());
// pre-fetch listener
SimpleMongoLazyLoadingListener loadingListener = SimpleMongoLazyLoadingListener.create(mongoClient, "testDb", "testCol", Client.class, BarbelHistoContext.getDefaultGson());
// locking listener
MongoPessimisticLockingListener lockingListener = MongoPessimisticLockingListener.create(mongoClient, "lockDb", "docLocks");
// BarbelHisto instance
BarbelHisto<Client> mongoBackedHisto = BarbelHistoBuilder.barbel().withSynchronousEventListener(updateListener)
                .withSynchronousEventListener(loadingListener).withSynchronousEventListener(lockingListener).build();

You can use your own MongoClient settings if you like. The BarbelHisto mongo package does provide a client creation class, for convenience. There are three listeners registered synchronously with BarbelHisto. The SimpleMongoUpdateListener will forward updates saved against BarbelHisto gagainst the mongo shadow collection. The SimpleMongoLazyLoadingListener listener ensures that data is fetched into the local BarbelHisto instance if cllients perform queries using the BarbelHisto.retrieve() methods. The MongoPessimisticLockingListener will lock journals in mongo, if the client performs an update using the BarbelHisto.save().

With this setup you can now store and retrieve bitemporal data with a mongo collection as data source.

Client client = new Client("1234", "Mr.", "Smith", "Martin", "some street 11", "somemail@projectbarbel.org", LocalDate.of(1973, 6, 20));
mongoBackedHisto.save(client, LocalDate.now(), LocalDate.MAX);

Later in other sessions of your web application, you can retrieve the client using the BarbelHisto.retrieve() from MongoDB.

Client client = mongoBackedHisto.retrieveOne(BarbelQueries.effectiveNow("1234"));

Use the BarbelQueries to make queries against the MongoDB backed BarbelHisto instance. You can also combine BarbelQueries.

List<Client> clients = mongoBackedHisto.retrieve(QueryFactory.and(BarbelQueries.effectiveNow("1234"),BarbelQueries.effectiveNow("1234")));

Be careful if you don`t specify IDs in your query. This might cause a full load of the mongo collection.

That's it. There is nothing more to do then this.

Let's access the version data for the client object we've just added. You've retrieved the clientpreviously in this tutorial.

Bitemporal clientBitemporal = (Bitemporal)client;
System.out.println(clientBitemporal.getBitemporalStamp().toString());

If you like to print out what MongoDB knows about your client, then pretty print the document journal like so:

System.out.println(mongoBackedHisto.prettyPrintJournal("1234"));

This yould return a printout that looks similar to this one:

Document-ID: 1234

|Version-ID                              |Effective-From |Effective-Until |State   |Created-By           |Created-At                                   |Inactivated-By       |Inactivated-At                               |Data                           |
|----------------------------------------|---------------|----------------|--------|---------------------|---------------------------------------------|---------------------|---------------------------------------------|-------------------------------|
|d18cd394-aa62-429b-a23d-46e935f80e71    |2019-03-01     |999999999-12-31 |ACTIVE  |SYSTEM               |2019-03-01T10:46:27.236+01:00[Europe/Berlin] |NOBODY               |2199-12-31T23:59:00Z                         |EffectivePeriod [from=2019-03- |

You can get the complete code from this tutorial in this test case.