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JavaBeginner#spring
JavaIntermediate#spring
What are the different types of dependency injection in Spring?
Constructor injection (recommended, immutable, testable), setter injection (optional dependencies), and field injection (@Autowired directly on a field, discouraged for testability reasons).
Example
@Service
class OrderService {
private final PaymentService ps;
@Autowired
OrderService(PaymentService ps) { this.ps = ps; } // constructor injection
}