4.4.5.1. Programmatic Transaction Management

Programmatic transaction management is done using com.haulmont.cuba.core.Transaction interface, a reference to which may be obtained via the createTransaction() or getTransaction() methods of the Persistence infrastructure interface.

The createTransaction() method creates a new transaction and returns the Transaction interface. Subsequent calls of commit(), commitRetaining(), end() methods of this interface control the created transaction. If at the moment of creation there was another transaction, it will be suspended and resumed after the completion of the newly created one.

The getTransaction() method either creates a new transaction or attaches to an existing one. If at the moment of the call there is an active transaction, then the method completes successfully, but subsequent calls of commit(), commitRetaining(), end() have no influence on the existing transaction. However calling end() without a prior call to commit() will mark current transaction as RollbackOnly.

Examples of programmatic transaction management:

@Inject
private Metadata metadata;
@Inject
private Persistence persistence;
...
// try-with-resources style
try (Transaction tx = persistence.createTransaction()) {
    Customer customer = metadata.create(Customer.class);
    customer.setName("John Smith");
    persistence.getEntityManager().persist(customer);
    tx.commit();
}
// plain style
Transaction tx = persistence.createTransaction();
try {
    Customer customer = metadata.create(Customer.class);
    customer.setName("John Smith");
    persistence.getEntityManager().persist(customer);
    tx.commit();
} finally {
    tx.end();
}

Transaction interface has also the execute() method accepting an action class or a lambda expression. The action will be performed in the transaction. This enables organizing transaction management in functional style, for example:

UUID customerId = persistence.createTransaction().execute((EntityManager em) -> {
    Customer customer = metadata.create(Customer.class);
    customer.setName("ABC");
    em.persist(customer);
    return customer.getId();
});

Customer customer = persistence.createTransaction().execute(em ->
        em.find(Customer.class, customerId, "_local"));

Keep in mind that execute() method of a given instance of Transaction may be called only once because the transaction ends after the action code is executed.