Top 20 Spring Boot Interview Questions for Freshers (2026 Edition): The Ultimate Cheat Sheet

Don’t Panic, It’s Just Frameworks

If you are a fresher walking into a Java interview in 2026, there is one guarantee: You will be asked about Spring Boot.

Colleges often teach “Core Java” (Loops, OOPs, Collections), but companies build software on Spring Boot. The gap between what you know and what they need is where the interview happens.

This isn’t just a list of definitions to memorize. As a Senior Developer, I have curated these questions to show you what we are actually looking for: not just “What is X?”, but “Do you understand why we use X?”

Let’s crack this interview.

Part 1: The Core Concepts (The “Must Knows”)

These are the warm-up questions. If you miss these, the interview is usually over.

Q1. What is the main difference between Spring and Spring Boot?

• The “Bookish” Answer: Spring is the framework; Spring Boot is a tool to create Spring applications easily.
• The “Hired” Answer: “Spring is the engine, but it requires a lot of manual configuration (XML files, server setup). Spring Boot is the car that comes pre-assembled. It uses Auto-Configuration to set up everything automatically, so I can focus on writing business logic instead of spending days configuring web.xml.”

Q2. What does the @SpringBootApplication annotation do?

This is the most common question. It is actually a “wrapper” for three other annotations:

1. @Configuration: Marks the class as a source of bean definitions.
2. @EnableAutoConfiguration: Tells Spring Boot to start adding beans based on classpath settings (the magic part).
3. @ComponentScan: Tells Spring to look for other components (@Controller, @Service) in the current package.

Q3. Explain Dependency Injection (DI) to a 5-year-old.

• The Answer: “Dependency Injection is like ordering a pizza instead of making it yourself.
  • Without DI: My code has to say Pizza p = new Pizza(); (I make it myself).
  • With DI: I just say @Autowired Pizza p;. The Spring Framework (the delivery guy) brings the Pizza to me. I don’t care how it was made; I just use it.”

Q4. What are “Starters” in Spring Boot?

Answer: Starters are dependency descriptors. Instead of manually adding 10 different JAR files for a web app (Spring MVC, Jackson, Tomcat, Validation), I just add one dependency in my pom.xml: spring-boot-starter-web. It pulls in everything else automatically.

Q5. How does a Spring Boot application run without installing Tomcat?

Answer: Spring Boot includes an Embedded Server (usually Tomcat, Jetty, or Undertow) inside the JAR file. When you run the application, it spins up the server internally. You don’t deploy to a server; the server is part of your app.

Part 2: Building REST APIs (The Daily Job)

This is what you will be doing 90% of the time as a Junior Dev.

Q6. @RestController vs. @Controller: What’s the difference?

• @Controller: Used for traditional web pages (returning HTML/JSP).
• @RestController: Used for REST APIs. It automatically adds @ResponseBody to every method, meaning the return value is sent directly as JSON, not as an HTML page.

Q7. What is the difference between @RequestBody and @RequestParam?

• @RequestBody: Extracts data from the JSON body of the request (e.g., a user saving a registration form).Java

// POST /users with JSON { "name": "John" }
public User save(@RequestBody User u) { ... }

// GET /users?role=admin
public List<User> get(@RequestParam String role) { ... }

Q8. Explain the HTTP Methods: GET, POST, PUT, DELETE.

• GET: Read data (Safe, does not change server state).
• POST: Create new data (Not idempotent—sending it twice creates two records).
• PUT: Update/Replace existing data (Idempotent—sending it twice gives the same result).
• DELETE: Remove data.

Q9. How do you return a “404 Not Found” status code?

Answer: “I would use ResponseEntity. It allows me to control the body, headers, and status code.”

if (user == null) {
    return ResponseEntity.status(HttpStatus.NOT_FOUND).body("User missing");
}

Part 3: Data & Database (JPA)

Q10. What is JpaRepository?

Answer: It is an interface that gives me ready-made database methods like save(), findAll(), findById(), and delete(). I don’t have to write SQL queries for basic CRUD operations; Spring Data generates them for me.

Q11. What is the H2 Database and why do freshers use it?

Answer: H2 is an In-Memory Database. It is perfect for testing and learning because it requires zero installation. When the application stops, the data is lost, which gives me a clean slate every time I restart my code.

Q12. What is the difference between @Entity and @Table?

• @Entity: Tells Hibernate “This class represents a database table.” (Mandatory).
• @Table: Used if the table name in the DB is different from the Class name (e.g., class User but table users_tbl). (Optional).

Part 4: The “Scenario” Questions (The Interview Winners)

These questions test if you have actually coded or just read a PDF.

Q13. You run your app and see “Port 8080 is already in use.” What do you do?

Answer: “This means another application is using the default port. I would open application.properties and change the port using server.port=8081.”

Q14. How do you reload changes without restarting the server every time?

Answer: “I would use Spring Boot DevTools. It provides ‘Live Reload’ functionality, so whenever I save a file, the application restarts automatically in seconds.”

Q15. What is application.properties vs application.yml?

Answer: They both do the same thing (configuration).

• Properties: Standard Key=Value format (server.port=8080).
• YAML: Hierarchical format, easier to read for complex configs.

server:
  port: 8080

Q16. How do you read a value from application.properties into your Java code?

Answer: “I use the @Value annotation.”

@Value("${app.welcomeMessage}")
private String message;

Part 5: Advanced (Bonus Points)

Q17. What are “Profiles” in Spring Boot?

Answer: Profiles let us map configuration to environments. I can have application-dev.properties (for my local H2 DB) and application-prod.properties (for the real MySQL DB). I switch between them using spring.profiles.active=dev.

Q18. What is Actuator?

Answer: It is a library that adds production-ready features to help monitor the app. It exposes endpoints like /actuator/health to check if the app is up and running.

Q19. What is the difference between Constructor Injection and Field Injection?

• Field: @Autowired directly on the variable (Easier to write, harder to test).
• Constructor: @Autowired on the constructor (Recommended by Spring team because it ensures the class cannot be created without its dependencies).

Q20. Why is Spring Boot becoming “Native” in 2026?

Answer: “With Spring Boot 3+ and GraalVM, we can compile Java apps into Native Images. This makes them start in milliseconds and use very little memory, which is perfect for Cloud and Serverless environments.”

Conclusion: How to Practice

Don’t just memorize these. Open your IDE (IntelliJ or Eclipse) and build a simple “Student Management System”.

1. Create a Student class (@Entity).
2. Create a Repository (JpaRepository).
3. Create a Controller (@RestController).

If you can build that from scratch without Googling every step, you are ready for the job. Good luck!