What is Spring Framework Best Guide in 2025

In the Java ecosystem, the Spring Framework is a game-changer. It simplifies enterprise application development by offering powerful features, reusable modules, and flexible configurations. But if you’re new to Java or backend development, you might wonder — What is Spring Framework and why is it so widely used?

This blog post provides an in-depth, real-world explanation of the Spring Framework, perfect for beginners, students, and professionals.

🔹 Introduction to Spring Framework

Spring Framework is an open-source Java platform that provides comprehensive infrastructure support for developing robust Java applications.

It is one of the most widely used Java EE alternatives, known for simplifying development by offering features like Dependency Injection (DI), Aspect-Oriented Programming (AOP), and modular components.

🔹 Why Do We Need Spring?

Before Spring, developers relied heavily on:

• Complex J2EE specifications
• Boilerplate code for transactions, security, logging, and DB access
• Manual object creation and dependency management

Spring addresses all these pain points by:

• Promoting loosely coupled architecture
• Providing ready-to-use modules
• Supporting modern architectures like Microservices

🔹 Core Features of Spring Framework

1. Lightweight and modular
2. Inversion of Control
3. Aspect-Oriented Programming (AOP)
4. Transaction management
5. Integration with frameworks like Hibernate, JPA, JDBC
6. Support for REST, SOAP, JMS, Security
7. Spring Boot for rapid development

🔹 Spring Framework Architecture Overview

Spring follows a layered architecture, which means you can choose the modules you need without affecting others.

The architecture consists of several modules grouped into different layers:

----------------------------------
|       Spring Framework         |
----------------------------------
| Spring Core Container          |
| Spring AOP & Instrumentation   |
| Spring JDBC & ORM              |
| Spring Web (MVC, WebFlux)      |
| Spring Context                 |
| Spring Test                    |
----------------------------------

Let’s break down these layers.

🔹 Spring Core Container

This is the heart of the Spring Framework. It manages the beans, their lifecycle, and dependencies.

Key components:

• BeanFactory: Basic DI container
• ApplicationContext: Advanced container with lifecycle events
• Spring Beans: Java objects managed by Spring
• Dependency Injection (DI): Injects objects where required, reducing hard-coded dependencies

Example:

@Component
public class Engine {
    public String start() {
        return "Engine started";
    }
}

@Component
public class Car {
    @Autowired
    private Engine engine;

    public void drive() {
        System.out.println(engine.start());
    }
}

Spring automatically injects Engine into Car—this is the power of DI.

🔹 Spring AOP (Aspect-Oriented Programming)

AOP helps separate cross-cutting concerns like logging, security, and transactions from the business logic.

Example Use Case:

Add logging before and after a method execution:

@Aspect
@Component
public class LoggingAspect {
    @Before("execution(* com.app.service.*.*(..))")
    public void logBefore() {
        System.out.println("Method execution started");
    }

    @After("execution(* com.app.service.*.*(..))")
    public void logAfter() {
        System.out.println("Method execution finished");
    }
}

This cleanly separates business logic from logging logic.

🔹 Spring JDBC and ORM Modules

Spring simplifies database operations with support for:

• JDBC Template for SQL operations
• Hibernate
• JPA (Java Persistence API)

No more writing complex JDBC boilerplate code.

Example:

@Autowired
JdbcTemplate jdbc;

public int saveUser(User user) {
   String sql = "INSERT INTO users (name, email) VALUES (?, ?)";
   return jdbc.update(sql, user.getName(), user.getEmail());
}

🔹 Spring Web (Spring MVC)

Spring MVC is a Model-View-Controller web framework for building robust web apps and RESTful APIs.

Key Concepts:

• DispatcherServlet
• Controllers
• ViewResolvers
• Interceptors

Example:

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

With just a few annotations, you’ve built a REST API.

🔹 Spring Boot: The Game Changer

Spring Boot is a project under the Spring umbrella that removes boilerplate configuration and allows rapid development.

• Embedded servers (Tomcat, Jetty)
• Auto-configuration
• Production-ready features (metrics, health checks)

Example:

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

This simple file launches a full-fledged web application.

🔹 Spring Security

• Supports OAuth2, JWT, LDAP
• Easily integrates with Spring Boot

Example Use Case:

Securing endpoints:

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
   @Override
   protected void configure(HttpSecurity http) throws Exception {
       http
           .authorizeRequests()
           .antMatchers("/admin/**").hasRole("ADMIN")
           .anyRequest().authenticated()
           .and()
           .formLogin();
   }
}

🔹 Spring Testing Module

• Provides support for unit testing Spring components using JUnit, Mockito, and Spring TestContext
• MockBean and WebMvcTest simplify controller testing

🔹 Real-Time Example: Online Book Store App

Spring Modules Used:

• Spring MVC for web pages and REST APIs
• Spring Boot for setup and configuration
• Spring JPA to store book data in MySQL
• Spring Security to authenticate users
• Spring AOP for logging and tracking usage

This combination powers scalable, secure, and easily maintainable enterprise applications.

🔹 Benefits of Using Spring Framework

• ✅ Loose coupling via Dependency Injection
• 🧩 Modular and layered architecture
• 🚀 Rapid development with Spring Boot
• 🔒 Built-in security features
• 🔁 Reusable components
• 📦 Easy testing and integration with other frameworks

🔹 Common Spring Projects You Should Know

• Spring Boot – Auto-configuration and embedded servers
• Spring Cloud – Cloud-native microservices
• Spring Data – Simplified database access
• Spring Batch – Batch processing
• Spring Security – Authentication and authorization
• Spring Integration – Messaging and enterprise integration

🔹 When to Use Spring Framework?

• Developing Java web applications
• Building REST APIs
• Creating microservices
• Writing modular enterprise systems
• Securing applications with role-based access

Python History

🔹 Frequently Asked Questions

Q1: Is Spring Framework only for web applications?
No. Spring is a general-purpose framework suitable for standalone, web, and enterprise applications.

Q3: Is Spring better than other frameworks like Struts or JSF?
Yes, Spring has more flexibility, better modularity, and modern capabilities.

Theoretical Spring Framework Explained: Complete Guide for 2025

If you’re preparing for interviews, learning enterprise Java, or planning to build scalable web applications, understanding the theoretical aspects of Spring Framework is essential.

In this guide, we break down the core concepts, modules, and real-time usage examples of the Spring Framework. Whether you’re a beginner, student, or Java professional, this comprehensive explanation will help solidify your understanding.

Why Learn Theoretical Spring Framework?

• Interview Preparation: 90% of Java interviews ask Spring-related questions.
• Project Design: Helps in architecting maintainable and scalable applications.
• Conceptual Clarity: Understanding core concepts is a must before jumping into Spring Boot or Microservices.

Core Features of Spring Framework

• Dependency Injection (DI)
• Aspect-Oriented Programming (AOP)
• Modular Architecture
• Integration with other frameworks (JPA, Hibernate, etc.)
• Web MVC for building web apps
• Security, Data access, and Testing support

What is Inversion of Control (IoC)?

Inversion of Control is a design principle where the control of object creation and dependency management is given to a container (in Spring’s case, the IoC container).

Instead of creating objects manually with new, Spring injects required dependencies automatically.

Real-Time Example:

// Traditional approach
UserService userService = new UserService(new UserRepository());

// With Spring DI
@Autowired
private UserService userService;

What is Dependency Injection?

Dependency Injection (DI) is a core concept of Spring where one object supplies the dependencies of another. Spring supports:

• Constructor Injection
• Setter Injection
• Field Injection (with @Autowired)

Example:

@Component
public class BookService {
    private BookRepository repository;

    @Autowired
    public BookService(BookRepository repository) {
        this.repository = repository;
    }
}

What is the Spring IoC Container?

It is responsible for:

• Instantiating beans
• Managing their lifecycle
• Injecting dependencies

Types of Containers:

• BeanFactory
• ApplicationContext (most commonly used)

What are Beans in Spring?

• @Component
• @Service
• @Repository
• @Controller

What are the Bean Scopes?

1. Singleton (default): One bean per container.
2. Prototype: New bean every time requested.
3. Request (Web): One bean per HTTP request.
4. Session (Web): One bean per HTTP session.

What is Spring Configuration?

There are 3 ways to configure Spring applications:

1. XML Configuration
2. Annotation-based Configuration
3. Java-based Configuration

Example – Java-based config:

@Configuration
@ComponentScan("com.example")
public class AppConfig {
}

What is Spring AOP?

Aspect-Oriented Programming (AOP) is used to separate cross-cutting concerns like logging, security, and transaction management.

Core concepts:

• Aspect: Common functionality (e.g., Logging)
• Advice: Action to be taken (before/after method)
• JoinPoint: Point during execution
• Pointcut: Predicate to match JoinPoints

Real-Life Use Case of AOP

Imagine logging execution time for all service methods:

@Aspect
@Component
public class LoggingAspect {
    @Before("execution(* com.example.service.*.*(..))")
    public void logBeforeMethod(JoinPoint joinPoint) {
        System.out.println("Executing: " + joinPoint.getSignature());
    }
}

What is Spring MVC?

It follows the Model-View-Controller pattern to separate business logic, presentation, and navigation.

Example Controller:

@Controller
public class HomeController {
    @GetMapping("/")
    public String home() {
        return "home"; // home.jsp
    }
}

What are Annotations in Spring?

• @Component: Generic bean
• @Service: Service layer
• @Repository: DAO layer
• @Controller: Web MVC controller
• @Autowired: Dependency injection
• @Configuration: Java config class
• @Bean: Custom bean definition

What is the use of @Qualifier?

When multiple beans of the same type exist, @Qualifier helps Spring decide which one to inject.

@Autowired
@Qualifier("paypalService")
private PaymentService paymentService;

What is the role of @Primary?

@Primary
@Bean
public PaymentService stripeService() {
    return new StripePaymentService();
}

What is Spring JDBC?

Spring JDBC simplifies interaction with relational databases. It provides:

• JdbcTemplate
• Exception translation
• Transaction management

Example:

jdbcTemplate.update("INSERT INTO user (name) VALUES (?)", "John");

What is Spring Transaction Management?

Spring provides declarative transaction management using @Transactional.

Example:

@Transactional
public void transferFunds() {
    // debit and credit logic
}

What is the difference between BeanFactory and ApplicationContext?

What are Profiles in Spring?

Profiles help in defining different configurations for different environments (dev, test, prod).

@Profile("dev")
@Bean
public DataSource devDataSource() {
    return new HikariDataSource();
}

What is @Bean annotation?

Used to declare manual beans inside a configuration class.

@Bean
public RestTemplate restTemplate() {
    return new RestTemplate();
}

What are common exceptions in Spring?

• BeanCreationException
• NoSuchBeanDefinitionException
• UnsatisfiedDependencyException
• ApplicationContextException

How to test Spring Applications?

• @RunWith(SpringRunner.class)
• @SpringBootTest
• @MockBean
• @DataJpaTest

What is the purpose of @ComponentScan?

@ComponentScan tells Spring where to look for components (beans) to auto-register them in the container.

@ComponentScan(basePackages = "com.example.app")

It eliminates the need to declare beans manually for annotated classes like @Component, @Service, etc.

What is the use of @Configuration?

It replaces the need for XML configuration.

@Configuration
public class AppConfig {
  @Bean
  public MyService myService() {
      return new MyService();
  }
}

What is the use of @Value annotation?

@Value is used to inject values into fields from properties or environment variables.

@Value("${server.port}")
private int port;

Useful for externalizing configuration.

What is Spring Expression Language (SpEL)?

SpEL allows you to dynamically inject values, call methods, or evaluate conditions in Spring beans.

@Value("#{2 * 10}")
private int calculatedValue;

What is @PropertySource?

Used to load external property files into Spring’s Environment.

@PropertySource("classpath:application.properties")
public class AppConfig {}

How does @Autowired work internally?

Spring uses reflection and the IoC container to resolve and inject dependencies marked with @Autowired. If more than one matching bean is found, Spring throws an exception unless specified via @Qualifier.

Can we use Spring without a web server?

Yes. Spring Core and its IoC container can be used in non-web Java applications (CLI apps, desktop apps, etc.).

What is the use of @Lazy annotation?

@Lazy
@Component
public class HeavyComponent {}

What is Java-based configuration in Spring?

Instead of using applicationContext.xml, you can use Java classes annotated with @Configuration to configure the Spring container.

What is an ApplicationContext?

It is the central interface for Spring configuration, offering all BeanFactory features plus:

• AOP
• Internationalization
• Event propagation

What is the use of ApplicationContextAware?

This interface allows a bean to get a reference to the ApplicationContext it belongs to.

public class MyBean implements ApplicationContextAware {
    public void setApplicationContext(ApplicationContext ctx) {
        this.context = ctx;
    }
}

What is a BeanPostProcessor?

Used to perform operations before or after bean initialization.

public class CustomBeanPostProcessor implements BeanPostProcessor {}

This is often used in frameworks like Spring Security or custom logging.

What is a FactoryBean?

A special type of bean that returns an object created within the bean, not the FactoryBean itself.

public class MyFactoryBean implements FactoryBean<MyObject> {}

What is the difference between init-method and @PostConstruct?

Both are used to define initialization logic, but:

• @PostConstruct: Preferred in modern Spring apps
• init-method: XML-based config

What is the difference between destroy-method and @PreDestroy?

Both are used for bean destruction callbacks, with:

• @PreDestroy: Java-based
• destroy-method: XML-based

What are stereotypes in Spring?

Spring provides specialized annotations called stereotypes:

• @Component: generic bean
• @Repository: DAO layer
• @Service: business layer
• @Controller: web layer

They are semantically different and offer specific behaviors (like exception translation in @Repository).

How does Spring support RESTful services?

• @RestController
• @GetMapping, @PostMapping, etc.

@RestController
public class ApiController {
  @GetMapping("/hello")
  public String hello() {
    return "Hello, World!";
  }
}

What is a RestTemplate?

RestTemplate is a Spring-provided HTTP client used to make REST calls to external APIs.

ResponseEntity<String> response = restTemplate.getForEntity("http://example.com", String.class);

What is ResponseEntity?

return new ResponseEntity<>(data, HttpStatus.OK);

How does Spring handle file uploads?

Using MultipartFile in controllers:

@PostMapping("/upload")
public String upload(@RequestParam("file") MultipartFile file) {}

Requires multipart resolver configuration.

What is HandlerInterceptor in Spring MVC?

It allows pre- and post-processing of requests, like authentication or logging.

public class AuthInterceptor implements HandlerInterceptor {}

What is WebApplicationInitializer?

public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {}

What is DispatcherServlet?

It is the front controller in Spring MVC that handles all incoming requests and delegates them to appropriate handlers.

What is @SessionAttributes?

Used to store model attributes in session for reuse between requests.

@SessionAttributes("user")
public class UserController {}

What is the difference between @RequestParam and @PathVariable?

• @RequestParam: Extracts query parameters (?id=5)
• @PathVariable: Extracts from URL path (/user/5)

What is the role of Model and ModelAndView?

Used to pass data from controllers to views (like JSPs or Thymeleaf templates).

How does Spring manage exception handling?

Using:

• @ExceptionHandler: Handle specific exceptions
• @ControllerAdvice: Global exception handler

What is Thymeleaf in Spring?

Thymeleaf is a modern server-side Java template engine used for generating HTML views in Spring MVC applications.

What is Spring Data?

Part of the Spring ecosystem, Spring Data simplifies data access layers using JPA and repository patterns.

public interface UserRepository extends JpaRepository<User, Long> {}

What is the difference between Spring and Spring Boot?

What is the use of @EnableAutoConfiguration?

Used in Spring Boot, it tells Spring to guess and configure your application based on the dependencies present in the classpath.

🔚 Conclusion

The Spring Framework is the foundation of modern Java development. With its comprehensive feature set, it empowers developers to build everything from simple REST APIs to complex enterprise applications. By learning Spring, you open the door to a wide range of job opportunities and scalable project capabilities.

Whether you’re a student exploring backend development or a developer upgrading from traditional Java EE, Spring offers a robust and flexible foundation to build upon.