Spring Boot Fundamentals

Spring Boot is a powerful framework that makes it easy to create stand-alone, production-grade Spring-based applications. This guide covers the fundamental concepts every developer should know.

What is Spring Boot?

Spring Boot is an extension of the Spring framework that eliminates the boilerplate configurations required for setting up a Spring application. It provides:

• Auto-configuration
• Starter dependencies
• Embedded servers
• Production-ready features

Creating Your First Application

Project Setup

Create a new Spring Boot project using Spring Initializr or your IDE:

@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

Creating a REST Controller

@RestController
@RequestMapping("/api")
public class HelloController {
    
    @GetMapping("/hello")
    public String hello() {
        return "Hello, World!";
    }
    
    @GetMapping("/hello/{name}")
    public String helloName(@PathVariable String name) {
        return "Hello, " + name + "!";
    }
}

Key Concepts

Dependency Injection

Spring Boot uses dependency injection to manage object dependencies:

@Service
public class UserService {
    
    private final UserRepository userRepository;
    
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
    
    public User findById(Long id) {
        return userRepository.findById(id)
            .orElseThrow(() -> new UserNotFoundException("User not found"));
    }
}

Auto-Configuration

Spring Boot automatically configures your application based on the dependencies you have added. This reduces the need for manual configuration.

Best Practices

1. Use constructor injection instead of field injection
2. Keep your controllers thin - business logic should be in services
3. Use proper HTTP status codes in your REST APIs
4. Implement proper exception handling

Conclusion

Spring Boot simplifies Java development by providing sensible defaults and reducing boilerplate code. Understanding these fundamentals will help you build robust and maintainable applications.