Yaya @Transactional ke aiki, ciki har da propagation da rollback?

Question

IT Interview Practice · Accepted Answer

`@Transactional` yana nannaɗe hanya cikin transaction na database: Spring yana buɗe ɗaya kafin hanyar ta gudana kuma yana commit lokacin da ta dawo daidai — ko kuma **rolls back** idan ta jefa. A ƙarƙashin murfin, **AOP proxy** ne, wanda shi ne tushen yawancin matsalolin.

## Amfani na asali

```java
@Service
public class TransferService {

@Transactional // commit on success, roll back on RuntimeException
    public void transfer(Long from, Long to, BigDecimal amount) {
        accounts.debit(from, amount);
        accounts.credit(to, amount); // if THIS throws, the debit is rolled back too
    }
}
```

## Ƙa'idar rollback ta tsoho (tarko na gargajiya)

Ta tsoho Spring yana rollback kawai a kan exceptions na **unchecked** (`RuntimeException`) da `Error` — **ba** a kan checked exceptions ba. Idan ka jefa checked exception, transaction ɗin *yana commit*. Rufe shi a fili:

```java
@Transactional(rollbackFor = Exception.class) // roll back on checked too
public void process() throws IOException { /* ... */ }
```

## Propagation

Propagation yana yanke shawarar abin da zai faru lokacin da hanyar transactional ta kira wata:

- **REQUIRED** (tsoho): shiga transaction na mai kira, ko fara ɗaya idan babu.
- **REQUIRES_NEW**: dakatar da transaction na mai kira sannan gudana a cikin sabo mai zaman kansa — mai amfani ga audit logs da dole su dawwama ko da aikin waje ya rollback.

```java
@Transactional(propagation = Propagation.REQUIRES_NEW)
public void writeAuditLog(String event) { /* commits independently */ }
```

## Tarkon self-invocation

Saboda `@Transactional` yana aiki ta proxy, kiran hanyar `@Transactional` guda daga wata hanya *a cikin aji ɗaya* yana ƙetare proxy — ana yin watsi da annotation shiru. Kira a tsakanin beans, ko inject self.

## Me ya sa yake da muhimmanci

Transactions su ne inda daidaiton bayanai ke rayuwa, don haka masu tambayoyin hira suna matsawa da ƙarfi anan. Ƙa'idar rollback na checked-exception da bug ɗin self-invocation su ne tambayoyi biyu da ke amincewa raba mutanen da suka *yi amfani* da `@Transactional` daga waɗanda suka *fahimce* shi.

Amfani na asali

Ƙa'idar rollback ta tsoho (tarko na gargajiya)

Propagation

Tarkon self-invocation

Me ya sa yake da muhimmanci

Tambayoyi masu alaƙa