Chapter 2. Short example

For example, using the entities defined above, the following code will generate revision number 1, which will contain two new Person and two new Address entities:

entityManager.getTransaction().begin();

Address address1 = new Address("Privet Drive", 4);
Person person1 = new Person("Harry", "Potter", address1);

Address address2 = new Address("Grimmauld Place", 12);
Person person2 = new Person("Hermione", "Granger", address2);

entityManager.persist(address1);
entityManager.persist(address2);
entityManager.persist(person1);
entityManager.persist(person2);

entityManager.getTransaction().commit();

Now we change some entities. This will generate revision number 2, which will contain modifications of one person entity and two address entities (as the collection of persons living at address2 and address1 changes):

entityManager.getTransaction().begin();

Address address1 = entityManager.find(Address.class, address1.getId());
Person person2 = entityManager.find(Person.class, person2.getId());

// Changing the address's house number
address1.setHouseNumber(5)

// And moving Hermione to Harry
person2.setAddress(address1);

entityManager.getTransaction().commit();

We can retrieve the old versions (the audit) easily:

AuditReader reader = AuditReaderFactory.get(entityManager);

Person person2_rev1 = reader.find(Person.class, person2.getId(), 1);
assert person2_rev1.getAddress().equals(new Address("Grimmauld Place", 12));

Address address1_rev1 = reader.find(Address.class, address1.getId(), 1);
assert address1_rev1.getPersons().getSize() == 1;

// and so on