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. VictorRentea.ro
@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

2. VictorRentea.ro
@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. VictorRentea.ro3 JPA – Runtime
class B {
@Transactional(propag=???)
public void b() { ... }
}
@Autowired private B b;
public void a() { b.b(); }
How does it work?
proxy
@Transactional
I can do more stuff
before calling the real b()

4. VictorRentea.ro
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. VictorRentea.ro
PC2
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. VictorRentea.ro
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=…)