What are the main functions and tasks implemented by the Spring framework in applications?

Spring is a popular Java framework that simplifies the development of enterprise applications. Main features and tasks of Spring:

• Inversion of Control (IoC) and Dependency Injection (DI): managing the creation and relationships of objects, which makes testing and maintaining code easier.
• Transaction management: simplifies working with transactions in databases.
• Modularity: provides many modules for different tasks — Spring MVC for web applications, Spring Data for database operations, Spring Security for security, etc.
• Aspect-Oriented Programming (AOP): allows injecting additional behavior (logging, security) without changing business logic.

Example of a simple component with dependency injection:

@Component
public class UserService {
    private final UserRepository userRepository;

    @Autowired
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public User findUser(Long id) {
        return userRepository.findById(id);
    }
}