Spring @Transactional Explained
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The document discusses transaction management in Java Persistence API (JPA), focusing on the use of the @Transactional annotation and its various propagation types such as supports, mandatory, required, and others. It outlines the behavior of these transactions in the context of service classes and the EntityManager, including aspects like committing, rolling back, and error handling. Additionally, it touches on AOP proxies and transaction interception in relation to method calls with @Transactional annotations.
Spring @Transactional Explained
- 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=…)