Constructor injection (preferred) in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a constructor for dependency injection in a Spring Boot component.

Spring Boot

public class UserService {
    private final UserRepository userRepository;

    public UserService([1] userRepository) {
        this.userRepository = userRepository;
    }
}

Drag options to blanks, or click blank then click option'

AUserRepository

Bvoid

Cint

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using a primitive type like int instead of the dependency class.

Using void as a parameter type, which is invalid.

The constructor parameter must be the type of the dependency to inject, here UserRepository.

2fill in blank

medium

Complete the code to annotate the class as a Spring component for constructor injection.

Spring Boot

[1]
public class OrderService {
    private final PaymentService paymentService;

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

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A@Autowired

B@ComponentScan

C@Repository

D@Service

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Autowired on the class instead of on the constructor or fields.

Using @ComponentScan which is for configuration classes.

The @Service annotation marks the class as a Spring service component, enabling constructor injection.

3fill in blank

hard

Fix the error in the constructor injection by completing the annotation for automatic wiring.

Spring Boot

public class NotificationService {
    private final EmailSender emailSender;

    [1]
    public NotificationService(EmailSender emailSender) {
        this.emailSender = emailSender;
    }
}

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A@Service

B@Inject

C@Autowired

D@Component

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Service or @Component on the constructor instead of the class.

Using @Inject which is a Java EE annotation, not Spring-specific.

The @Autowired annotation tells Spring to inject the dependency via the constructor.

4fill in blank

hard

Fill both blanks to complete a Spring component with constructor injection and final field declaration.

Spring Boot

@Component
public class [1] {
    private final [2] repository;

    public [1]([2] repository) {
        this.repository = repository;
    }
}

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AProductService

BUserRepository

COrderRepository

DCustomerService

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching class name and constructor parameter types.

Using service names as repository types.

The class name and the field type must match the service and repository names respectively for proper constructor injection.

5fill in blank

hard

Fill all three blanks to complete a Spring service class with constructor injection and proper annotations.

Spring Boot

[1]
public class [2] {
    private final [3] paymentGateway;

    public [2]([3] paymentGateway) {
        this.paymentGateway = paymentGateway;
    }
}

Drag options to blanks, or click blank then click option'

A@Service

BPaymentService

CPaymentGateway

D@Component

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Component instead of @Service for service classes.

Mismatching class and parameter names.

The class must be annotated with @Service, named PaymentService, and inject a PaymentGateway dependency.