Spring @Transactional Explained

Backing slides for the mini-talk requested by the audience about how Spring @Transactional actually works. (Extract from my Spring Framework Training). See www.victorrentea.ro/#spring for more details about the full training

1. @Transactional 1 JPA – Runtime @Transactional (propagation = Propagation. SUPPORTS ) public class EmployeeService { public void getEmployee( long employeeId) { ... } @Transactional (propagation = Propagation. MANDATORY ) public void createEmployee(Employee employee) { ... } } Works via an AOP Proxy wrapping the EmployeeService "inherits" this "override" ? ? ?

2. @Transactional  Life 2 JPA – Runtime Account Service Account Repo Transfer Service payEnelBill () getAccount SUPPORTS payBill () COMMIT MANDATORY @ Transactional ( propagation = REQUIRED ) Persistence Context @PersistenceContext private EntityManager em ; Inject an EntityManager proxy em .find(...) em .find(...)

3. 3 JPA – Runtime class B { @Transactional (propag= ??? ) public void b() { ... } } @Autowired private B b; public void a() { b.b(); } You don't get B.class ! How does it work? proxy calls calls @Transactional You get a Proxy ! I can do more stuff before calling the real b()

4. Propagation 4 JPA – Runtime supports required =default requires new mandatory not supported never nested ! class B { @Transactional (propag= ??? ) public void b() { ... } } @Autowired private B b; public void a() { b.b(); } existing Tx no Tx a b a b pause Tx ex ex Caller Tx New Tx No Tx @Transactional on ex, only this is lost (SAVEPOINT)

5. PC 2 REQUIRES_NEW @Transactional  Life 5 JPA – Runtime Account Service Account Repo Transfer Service payEnelBill () getAccount SUPPORTS payBill () ROLLBACK MANDATORY REQUIRED Persistence Context em .find(...) Error Repo @PersistenceContext private EntityManager em ; try { } catch (e) { } REQUIRED em .persist(error) tx.setRollbackOnly () persistError() COMMIT Ex

6. Throw a RuntimeException from a method, if: The method allows the Tx to enter, and The method is aspected by TransactionInterception When is a method Tx-aspected ? If there is any @Transactional in that class ? How do you kill a @ Tx ? 6 JPA – Runtime This one actually kills the Tx Can be customized: @Transactional ( rollbackFor =…, noRollbackFor =…)