Spring Framework

The Spring Framework is a powerful, feature-rich, and widely used open-source framework for building enterprise-level Java applications. It simplifies the development process by providing comprehensive infrastructure support for developing Java applications.

🧩 Key Features of Spring Framework

1. Lightweight and Modular

Core features can be used independently.
You can include only the parts you need (e.g., Spring Core, Spring MVC, Spring Security).

2. Inversion of Control (IoC) / Dependency Injection (DI)

Objects are given their dependencies at runtime by an external source.
Promotes loose coupling and easier testing.

@Component
public class Car {
    private Engine engine;

    @Autowired
    public Car(Engine engine) {
        this.engine = engine;
    }
}

3. Aspect-Oriented Programming (AOP)

Separates cross-cutting concerns like logging, transactions, and security.

@Aspect
@Component
public class LoggingAspect {
    @Before("execution(* com.example.service.*.*(..))")
    public void logBefore() {
        System.out.println("Logging before method execution");
    }
}

4. Spring MVC

Web framework for building RESTful and traditional web applications.
Follows the Model-View-Controller (MVC) design pattern.

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello, Spring!";
    }
}

5. Transaction Management

Programmatic and declarative transaction management using @Transactional.

@Service
public class PaymentService {
    @Transactional
    public void processPayment() {
        // transaction logic
    }
}

6. Spring Security

Provides authentication, authorization, and protection against common attacks (e.g., CSRF, XSS).

7. Spring Data JPA

Simplifies database access using repositories and eliminates boilerplate code.

public interface UserRepository extends JpaRepository<User, Long> {
    User findByUsername(String username);
}

8. Spring Boot

Rapid development, production-ready applications.
Embedded servers (Tomcat/Jetty), auto-configuration, and minimal configuration.

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

🧱 Spring Modules

Module	Purpose
Spring Core	Core container, IoC, and DI
Spring AOP	Aspect-Oriented Programming
Spring Data	Easy data access and persistence
Spring ORM	Integration with Hibernate, JPA
Spring Web	Web and RESTful services
Spring MVC	Model-View-Controller web framework
Spring Security	Authentication and authorization
Spring Boot	Simplified configuration and rapid development
Spring Batch	Batch processing framework
Spring Cloud	Microservices infrastructure and distributed systems

🧪 Spring Development Workflow

Define POJOs (Plain Old Java Objects)
Configure Beans using annotations or XML
Enable component scanning
Use Dependency Injection to wire components
Create REST or Web controllers
Access databases using Spring Data or JDBC
Secure your application with Spring Security

🔧 Tools Commonly Used with Spring

Maven/Gradle: Build tools
Thymeleaf: Templating engine for Spring MVC
PostgreSQL/MySQL: Databases
JUnit/Mockito: Testing frameworks
Lombok: Reduce boilerplate code
Docker: Containerization

📦 Spring vs Spring Boot

Feature	Spring Framework	Spring Boot
Setup	Manual configuration	Auto-configuration
Deployment	Requires external server	Embedded servers
Configuration Files	XML/Java Config	Minimal config + YAML/Props
Learning Curve	Steeper	Easier and quicker to start