Jlentrehake bean scope lan callback siklus urip ing Spring.

Question

IT Interview Practice · Accepted Answer

**Bean scope** ngontrol pira akeh instansi sing digawe container lan sepira suwene urip. **Callback siklus urip** ngidini kowe mlayokake kode pas sawise sawijining bean disusun lan pas sadurunge iku dirusak.

## Scope sing pancen kowe enggo

- **singleton** (default): *siji* instansi sing dienggo bareng per container. Digawe kanthi eager nalika wiwitan.
- **prototype**: instansi *anyar* saben bean dijaluk/disuntik.
- **request** / **session**: siji instansi per request utawa session HTTP (mung aplikasi web).

```java
@Service // singleton by default — one shared OrderService for the whole app
public class OrderService { }

@Component
@Scope("prototype") // fresh instance on every getBean/inject
public class ReportBuilder { }
```

**Jebakan klasik:** nyuntik prototype menyang singleton. Singleton dikabel *sepisan*, mula iku njaga siji instansi prototype ing salawase — janji "anyar saben wektu" rusak. Benerake nganggo `@Lookup`, `ObjectProvider<ReportBuilder>`, utawa scoped-proxy.

## Callback siklus urip

```java
@Component
public class ConnectionPool {

@PostConstruct // runs after dependencies are injected, before use
    public void open() { /* open sockets, warm caches */ }

@PreDestroy // runs on graceful container shutdown (singletons only)
    public void close() { /* release resources */ }
}
```

Penting: Spring **ora** nyeluk `@PreDestroy` ing bean prototype — iku nyerahake lan mandheg nglacak, mula *kowe* sing nduweni resik-resike.

## Kenapa iki penting

Iki misahake wong sing nganggep Spring minangka sihir karo wong sing ngerti container. Bug singleton-nyekel-prototype iku skenario wawancara favorit amarga iku alus lan nyebabake bug produksi nyata. Ngerti yen singleton kudu **stateless lan thread-safe** (dienggo bareng ing kabeh thread request) iku pesen praktis sing dirungokake pewawancara.

Scope sing pancen kowe enggo

Callback siklus urip

Kenapa iki penting

Pitakon sing gegandhengan