Spring Interview Prep 01

About @Autowired

In the context of Spring Framework (a popular Java framework), @Autowired is an annotation used for dependency injection. It tells Spring to automatically resolve and inject a bean (an object managed by the Spring container) into a class's field, constructor, or method.

How @Autowired Works

Dependency Injection:

When Spring detects the @Autowired annotation on a field, constructor, or method, it searches for a bean that matches the type. If found, Spring injects the dependency automatically.

Bean Resolution:

By Type: Spring matches the type of the field or parameter. By Name (Optional): If multiple beans of the same type exist, Spring may use the bean name for disambiguation (using @Qualifier or bean names in the configuration).

Scope:

@Autowired can inject singleton beans, prototype beans, or beans of other scopes.

Common Usage

1. Field Injection

@Component
public class MyService {
    @Autowired
    private MyRepository myRepository;

    public void performAction() {
        myRepository.save();
    }
}

2. Constructor Injection Constructor injection is the recommended approach as it supports immutability and easier testing.

@Component
public class MyService {
    private final MyRepository myRepository;

    @Autowired
    public MyService(MyRepository myRepository) {
        this.myRepository = myRepository;
    }

    public void performAction() {
        myRepository.save();
    }
}

3.Setter Injection

@Component
public class MyService {
    private MyRepository myRepository;

    @Autowired
    public void setMyRepository(MyRepository myRepository) {
        this.myRepository = myRepository;
    }

    public void performAction() {
        myRepository.save();
    }
}

Here is a Youtube playlist that features Spring.

I will add more to this blog series as I learn.