Spring vs Spring Boot

Spring and Spring Boot are frameworks in the Java ecosystem that simplify the development of robust and scalable applications. They are widely used by developers to build enterprise-level solutions with ease and efficiency. While both serve similar purposes, they differ in configuration, setup, and ease of use.

• Helps in building scalable and maintainable Java applications
• Simplifies development using modular and reusable components
• Widely used for enterprise and microservices-based architectures

Spring 

Spring is a comprehensive Java framework that provides support for building robust and scalable enterprise applications. It focuses on dependency injection, aspect-oriented programming, and modular architecture.

• Dependency Injection (DI): Simplifies object creation and management, promoting loose coupling.
• Modular Framework: Offers various modules like Spring MVC, Spring Security, Spring Data, allowing selective use.
• Flexible Configuration: Supports XML, annotations, and Java-based configuration for application setup.

Example: Spring application manually configured with beans and controllers:

@Configuration
@ComponentScan(basePackages = "com.example")
public class AppConfig {
    @Bean
    public UserService userService() {
        return new UserServiceImpl();
    }
}

@Controller
@RequestMapping("/users")
public class UserController {
    @Autowired
    private UserService userService;

    @GetMapping
    public String getUsers(Model model) {
        model.addAttribute("users", userService.getAllUsers());
        return "userList"; // JSP or HTML view
    }
}

// Main class deployed as WAR on external server like Tomcat
public class Main {
    public static void main(String[] args){
        
        // Deploy this app manually to an external server
    }
}

Explanation: This is a traditional Spring MVC application using Java-based configuration, where beans are defined manually and components are scanned for dependency injection. The application is deployed as a WAR file on an external server like Tomcat, with a controller handling web requests and returning a view.

Spring Boot 

Spring Boot is a project built on top of Spring that simplifies the development of Spring applications by providing auto-configuration, embedded servers, and production-ready features. It is designed to reduce boilerplate code and setup complexity.

• Auto-Configuration: Automatically configures Spring applications based on the dependencies added.
• Embedded Servers: Comes with embedded Tomcat, Jetty, or Undertow, eliminating the need for external servers.
• Starter POMs: Provides ready-to-use dependencies to simplify build configuration.

Example: Spring Boot REST API with minimal configuration:

@SpringBootApplication
public class UserApplication{
    
    public static void main(String[] args) {
        
        // Embedded Tomcat runs automatically
        SpringApplication.run(UserApplication.class, args); 
    }
}

@RestController
@RequestMapping("/api/users")
public class UserController {
    private List<String> users = List.of("Alice", "Bob", "Charlie");

    @GetMapping
    public List<String> getUsers() {
        
        // Returns JSON response
        return users; 
    }
}

Explanation: This is a Spring Boot application that uses auto-configuration and an embedded server, so no manual setup or deployment is required. It exposes a REST API that directly returns JSON data instead of rendering a view.

Spring vs Spring Boot