These 15 Spring Questions Are Eliminating Java Developers in 2026 Interviews

Most candidates fail after Question #5. Here’s what interviewers are really testing behind every Spring Framework question.

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The Spring Interview Landscape Has Changed

A few years ago, Spring interviews were predictable.

Interviewers asked about Dependency Injection, Bean Lifecycle, and maybe the difference between Spring and Spring Boot. If you memorized a few definitions, you could survive.

That is no longer true.

Modern companies expect developers to understand how Spring works internally, how Spring Boot simplifies development, how microservices communicate, how transactions behave under load, and why applications fail in production.

I’ve spoken with developers preparing for interviews at startups, product companies, fintech firms, and large enterprises. One pattern keeps appearing.

Many candidates know how to write Spring code.

Very few know why Spring behaves the way it does.

That gap is exactly what interviewers look for.

In this article, we’ll walk through 15 Spring Framework interview questions that repeatedly appear in 2026 hiring rounds. These aren’t just answers to memorize. They are concepts every serious Java developer should understand.

1. What Is Dependency Injection and Why Is It Important?

This is usually the first Spring question.

Most candidates answer:

“Dependency Injection means Spring creates objects for us.”

While technically true, it misses the bigger picture.

Dependency Injection (DI) is a design pattern where an object’s dependencies are provided externally instead of being created inside the object itself.

Without DI:

public class OrderService {

private PaymentService paymentService =
            new PaymentService();
}

The class is tightly coupled.

Now imagine changing the payment implementation.

You must modify the code.

With Spring:

@Service
public class OrderService {

private final PaymentService paymentService;
    public OrderService(PaymentService paymentService) {
        this.paymentService = paymentService;
    }
}

Spring injects the dependency.

The service becomes easier to test, maintain, and extend.

The real purpose of DI is not convenience.

It is loose coupling.

2. What Is Inversion of Control (IoC)?

Many developers confuse IoC and DI.

Dependency Injection is actually one implementation of IoC.

Traditionally, applications control object creation.

With Spring, that control is inverted.

Instead of:

UserService service = new UserService();

Spring creates and manages objects.

The framework decides:

• When beans are created
• How they are initialized
• How dependencies are injected
• When they are destroyed

That’s why it’s called Inversion of Control.

The framework controls the lifecycle rather than the application code.

3. What Is a Spring Bean?

A Spring Bean is simply an object managed by the Spring IoC container.

Example:

@Service
public class UserService {
}

When Spring starts, it scans the application.

It detects the annotation.

Then it creates and manages an instance of the class.

That instance becomes a Spring Bean.

Interviewers often ask:

“What is the difference between a normal Java object and a Spring Bean?”

A normal Java object is managed by the JVM.

A Spring Bean is managed by Spring.

That’s the key distinction.

4. Explain Bean Scopes in Spring

By default, Spring uses Singleton scope.

@Service
public class UserService {
}

Only one instance exists.

Every request receives the same object.

Other scopes include:

Prototype

@Scope("prototype")

A new object is created every time.

Request

One bean per HTTP request.

Session

One bean per user session.

Application

One bean per servlet context.

A common interview question:

“Why is Singleton the default scope?”

Because creating objects repeatedly consumes memory and CPU.

Singletons improve performance and reduce resource usage.

5. What Is the Difference Between @Component, @Service, @Repository, and @Controller?

Many candidates say:

“They are all the same.”

Not exactly.

Technically, all are specialized versions of @Component.

However, they provide semantic meaning.

@Component

Generic Spring-managed component.

@Service

Business logic layer.

@Service
public class PaymentService {
}

@Repository

Database access layer.

@Repository
public class UserRepository {
}

@Controller

Handles web requests.

@Controller
public class UserController {
}

Interviewers want to know whether you understand architectural separation.

6. What Is Spring Boot and Why Was It Created?

Before Spring Boot, configuring Spring was painful.

Developers spent hours writing XML files.

Adding dependencies.

Configuring servers.

Managing application startup.

Spring Boot solved these problems.

It introduced:

• Auto Configuration
• Embedded Servers
• Starter Dependencies
• Production-ready monitoring

Instead of:

100 lines of configuration

You write:

@SpringBootApplication
public class Application {
}

And Spring Boot handles the rest.

That’s why it became the industry standard.

7. What Is Auto Configuration?

This question appears frequently in senior-level interviews.

Auto Configuration means Spring Boot automatically configures components based on dependencies present in the classpath.

For example:

Add:

spring-boot-starter-web

Spring automatically configures:

• DispatcherServlet
• Tomcat
• Jackson
• REST support

No manual setup required.

Internally, Spring Boot uses:

@EnableAutoConfiguration

which loads configuration classes conditionally.

This dramatically reduces boilerplate.

8. What Is the Difference Between @Autowired and Constructor Injection?

Many developers still use field injection.

@Autowired
private UserRepository repository;

It works.

But constructor injection is preferred.

public UserService(UserRepository repository) {
    this.repository = repository;
}

Why?

Because:

• Dependencies become explicit
• Easier testing
• Better immutability
• Prevents NullPointerExceptions

Senior interviewers often expect constructor injection as the preferred answer.

9. Explain Spring Bean Lifecycle

This is a favorite question for experienced developers.

Spring follows these steps:

Step 1

Bean Instantiation

new UserService()

Step 2

Dependency Injection

Spring injects dependencies.

Step 3

Initialization

Methods annotated with:

@PostConstruct

are executed.

Step 4

Bean Ready for Use

Application uses the bean.

Step 5

Destruction

Methods annotated with:

@PreDestroy

execute before shutdown.

Understanding this lifecycle helps troubleshoot startup and shutdown issues.

10. What Is AOP (Aspect-Oriented Programming)?

Most developers use AOP without realizing it.

Imagine logging.

Without AOP:

log.info();
service.call();
log.info();

Every method repeats logging logic.

AOP extracts cross-cutting concerns.

Examples:

• Logging
• Security
• Transactions
• Monitoring
• Auditing

Example:

@Aspect
public class LoggingAspect {
}

Spring applies the logic automatically.

Cleaner code.

Less duplication.

Better maintainability.

11. How Does @Transactional Work?

This question separates intermediate developers from advanced developers.

Most people know:

@Transactional
public void saveOrder() {
}

But few understand what happens internally.

Spring creates a proxy around the method.

When the method starts:

BEGIN TRANSACTION

When successful:

COMMIT

If an exception occurs:

ROLLBACK

The proxy manages everything automatically.

Interviewers often ask:

“Why does @Transactional sometimes not work?”

Because self-invocation bypasses the Spring proxy.

That’s a common production issue.

12. What Is the Difference Between BeanFactory and ApplicationContext?

BeanFactory is the basic IoC container.

ApplicationContext is an advanced version.

BeanFactory provides:

• Bean management
• Dependency injection

ApplicationContext adds:

• Event support
• Internationalization
• AOP integration
• Bean post-processing

In real-world applications:

ApplicationContext

is almost always used.

13. What Is Spring Security?

Security questions have become common in interviews.

Spring Security provides:

• Authentication
• Authorization
• CSRF protection
• Session management
• Password encryption

Example:

@Configuration
@EnableWebSecurity
public class SecurityConfig {
}

Instead of building security manually, Spring provides battle-tested solutions.

Modern enterprise systems rely heavily on Spring Security.

14. Explain REST Controllers in Spring

Spring makes building APIs straightforward.

@RestController
@RequestMapping("/users")
public class UserController {
}

Example endpoint:

@GetMapping("/{id}")
public User getUser() {
}

Spring automatically:

• Maps HTTP requests
• Converts JSON
• Handles serialization
• Generates responses

Interviewers often ask:

“Difference between @Controller and @RestController?”

@RestController combines:

@Controller
@ResponseBody

making API development easier.

15. What Happens When a Spring Boot Application Starts?

This is one of the most impressive answers you can give.

When the application starts:

SpringApplication.run()

Several things happen.

First, Spring creates the Application Context.

Then component scanning begins.

Beans are discovered.

Dependencies are injected.

Auto Configuration executes.

Embedded Tomcat starts.

REST endpoints register.

Security filters initialize.

Finally:

Application Started Successfully

appears in the logs.

Many candidates use Spring Boot daily without understanding this startup sequence.

Interviewers notice immediately when someone can explain it.

What Senior Interviewers Are Actually Testing

Something interesting happens in Spring interviews.

Interviewers rarely care about definitions.

They care about understanding.

Two candidates might answer:

“What is Dependency Injection?”

The first candidate gives a textbook definition.

The second explains how DI improves testability, reduces coupling, and enables flexible architectures.

Guess who gets hired.

The difference isn’t memorization.

It’s practical understanding.

That’s why senior interviews increasingly focus on internal behavior, production scenarios, transaction management, startup flow, and framework architecture.

If you understand the concepts behind these 15 questions, you’ll perform significantly better than candidates who simply memorize answers from interview cheat sheets.