Field injection and why to avoid it in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to inject a dependency using field injection.

Spring Boot

public class UserService {
    @Autowired
    private [1] userRepository;
}

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

AAutowired

BuserRepository

CUserService

DUserRepository

Attempts:

3 left

💡 Hint

Common Mistakes

Using the variable name instead of the type.

Using the class itself instead of the dependency type.

The field type must be the class or interface to inject, here UserRepository.

2fill in blank

medium

Complete the code to inject a dependency using constructor injection instead of field injection.

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'

AUserService

BUserRepository

CAutowired

DService

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name of the service instead of the dependency.

Forgetting to mark the constructor with @Autowired (optional in Spring Boot).

The constructor parameter type must match the dependency type UserRepository to be injected.

3fill in blank

hard

Fix the error in this field injection example by choosing the correct annotation to avoid issues.

Spring Boot

public class UserService {
    [1]
    private UserRepository userRepository;
}

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

A@Component

B@Inject

C@Autowired

D@Service

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Component or @Service on fields instead of classes.

Using @Inject without proper configuration.

@Autowired is the Spring annotation for field injection. Using it properly is required for Spring to inject the dependency.

4fill in blank

hard

Fill both blanks to rewrite field injection as constructor injection to improve testability and immutability.

Spring Boot

public class UserService {
    private final UserRepository userRepository;

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

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

AUserRepository

Bthis.userRepository

CuserRepository

DUserService

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning the field to itself instead of the parameter.

Using wrong parameter type.

The constructor parameter type is UserRepository, and the assignment uses the parameter userRepository.

5fill in blank

hard

Fill all three blanks to create a Spring component with constructor injection and avoid field injection pitfalls.

Spring Boot

@[1]
public class OrderService {
    private final OrderRepository orderRepository;

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

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

AService

BOrderRepository

CorderRepository

DComponent

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Component instead of @Service for service classes.

Mixing up parameter and field names in assignment.

@Service marks the class as a Spring service component. The constructor parameter type is OrderRepository, and the assignment uses the parameter orderRepository.