ApplicationContext và BeanFactory khác nhau thế nào?

BeanFactory và ApplicationContext đều là Spring IoC container, nhưng ApplicationContext là superset.

Feature	BeanFactory	ApplicationContext
Lazy loading	✅ Default	❌ Eager (singleton instantiate ngay)
AOP, @Transactional	❌	✅
Event publishing	❌	✅ (`ApplicationEvent`)
MessageSource (i18n)	❌	✅
Web context	❌	✅ (`WebApplicationContext`)
Auto-config, Starters	❌	✅

java

// BeanFactory — API thấp, không dùng trực tiếp trong thực tế
// (XmlBeanFactory đã bị xóa từ Spring 5; DefaultListableBeanFactory là impl hiện tại)

// ApplicationContext — dùng trong Spring Boot
@SpringBootApplication
public class App {
  public static void main(String[] args) {
    ApplicationContext ctx = SpringApplication.run(App.class, args);
    // ctx.getBean(UserService.class);
  }
}

Khi nào biết điều này quan trọng trong phỏng vấn:
- Giải thích lazy vs eager loading.
- ApplicationContext.publishEvent() cho application events:

java

@Component
class OrderService {
  @Autowired ApplicationEventPublisher events;

  void placeOrder(Order order) {
    orderRepo.save(order);
    events.publishEvent(new OrderPlacedEvent(order.getId()));
  }
}

@Component
class EmailNotifier {
  @EventListener
  void onOrder(OrderPlacedEvent event) {
    mailService.sendConfirmation(event.getOrderId());
  }
}

Kết luận: Spring Boot luôn dùng ApplicationContext. BeanFactory là low-level API, không dùng trực tiếp trong thực tế.

BeanFactory and ApplicationContext are both Spring IoC containers, but ApplicationContext is a superset.

Feature	BeanFactory	ApplicationContext
Lazy loading	✅ Default	❌ Eager (singletons instantiated at startup)
AOP, @Transactional	❌	✅
Event publishing	❌	✅ (`ApplicationEvent`)
MessageSource (i18n)	❌	✅
Web context	❌	✅ (`WebApplicationContext`)
Auto-config, Starters	❌	✅

java

// BeanFactory — low-level API, not used directly in practice
// (XmlBeanFactory was removed in Spring 5; DefaultListableBeanFactory is the current impl)

// ApplicationContext — used in Spring Boot
@SpringBootApplication
public class App {
  public static void main(String[] args) {
    ApplicationContext ctx = SpringApplication.run(App.class, args);
  }
}

Why this matters in interviews: explain lazy vs eager, event-driven patterns:

java

@Component
class OrderService {
  @Autowired ApplicationEventPublisher events;

  void placeOrder(Order order) {
    orderRepo.save(order);
    events.publishEvent(new OrderPlacedEvent(order.getId()));
  }
}

@Component
class EmailNotifier {
  @EventListener
  void onOrder(OrderPlacedEvent event) {
    mailService.sendConfirmation(event.getOrderId());
  }
}

Conclusion: Spring Boot always uses ApplicationContext. BeanFactory is a low-level API not used directly in practice.

Xem toàn bộ Spring & Spring Boot cùng filter theo level & chủ đề con.

Mở danh sách Spring & Spring Boot

ApplicationContext và BeanFactory khác nhau thế nào?

BeanFactory và ApplicationContext đều là Spring IoC container, nhưng ApplicationContext là superset.

Feature	BeanFactory	ApplicationContext
Lazy loading	✅ Default	❌ Eager (singleton instantiate ngay)
AOP, @Transactional	❌	✅
Event publishing	❌	✅ (`ApplicationEvent`)
MessageSource (i18n)	❌	✅
Web context	❌	✅ (`WebApplicationContext`)
Auto-config, Starters	❌	✅

java

// BeanFactory — API thấp, không dùng trực tiếp trong thực tế
// (XmlBeanFactory đã bị xóa từ Spring 5; DefaultListableBeanFactory là impl hiện tại)

// ApplicationContext — dùng trong Spring Boot
@SpringBootApplication
public class App {
  public static void main(String[] args) {
    ApplicationContext ctx = SpringApplication.run(App.class, args);
    // ctx.getBean(UserService.class);
  }
}

Khi nào biết điều này quan trọng trong phỏng vấn:
- Giải thích lazy vs eager loading.
- ApplicationContext.publishEvent() cho application events:

java

@Component
class OrderService {
  @Autowired ApplicationEventPublisher events;

  void placeOrder(Order order) {
    orderRepo.save(order);
    events.publishEvent(new OrderPlacedEvent(order.getId()));
  }
}

@Component
class EmailNotifier {
  @EventListener
  void onOrder(OrderPlacedEvent event) {
    mailService.sendConfirmation(event.getOrderId());
  }
}

Kết luận: Spring Boot luôn dùng ApplicationContext. BeanFactory là low-level API, không dùng trực tiếp trong thực tế.

BeanFactory and ApplicationContext are both Spring IoC containers, but ApplicationContext is a superset.

Feature	BeanFactory	ApplicationContext
Lazy loading	✅ Default	❌ Eager (singletons instantiated at startup)
AOP, @Transactional	❌	✅
Event publishing	❌	✅ (`ApplicationEvent`)
MessageSource (i18n)	❌	✅
Web context	❌	✅ (`WebApplicationContext`)
Auto-config, Starters	❌	✅

java

// BeanFactory — low-level API, not used directly in practice
// (XmlBeanFactory was removed in Spring 5; DefaultListableBeanFactory is the current impl)

// ApplicationContext — used in Spring Boot
@SpringBootApplication
public class App {
  public static void main(String[] args) {
    ApplicationContext ctx = SpringApplication.run(App.class, args);
  }
}

Why this matters in interviews: explain lazy vs eager, event-driven patterns:

java

@Component
class OrderService {
  @Autowired ApplicationEventPublisher events;

  void placeOrder(Order order) {
    orderRepo.save(order);
    events.publishEvent(new OrderPlacedEvent(order.getId()));
  }
}

@Component
class EmailNotifier {
  @EventListener
  void onOrder(OrderPlacedEvent event) {
    mailService.sendConfirmation(event.getOrderId());
  }
}

Conclusion: Spring Boot always uses ApplicationContext. BeanFactory is a low-level API not used directly in practice.

Xem toàn bộ Spring & Spring Boot cùng filter theo level & chủ đề con.

Mở danh sách Spring & Spring Boot