Spring Framework FAQ: Top Questions

Spring performs Dependency Injection (DI) to decouple object creation and its dependencies. It supports constructor, setter, and field injection.

📘 Types of Injection:

• Constructor Injection: Dependencies provided at object creation.
• Setter Injection: Dependencies injected via setters.
• Field Injection: Using @Autowired directly on fields.

📥 Example:

@Component
public class OrderService {
  private final PaymentService paymentService;

  @Autowired
  public OrderService(PaymentService paymentService) {
    this.paymentService = paymentService;
  }
}

🏆 Expected Output:

OrderService is created with a fully injected PaymentService bean.

🛠️ Use Cases:

• Cleaner code, easier testing and maintenance.
• Supports both optional and mandatory dependencies.