DEV Community: Jitendra Rawat

📘 Top Spring Boot Interview Questions and Answers

Jitendra Rawat — Fri, 02 May 2025 23:06:32 +0000

🚀 Introduction

Spring Boot simplifies backend development by reducing boilerplate code, auto-configuring dependencies, and enabling fast delivery of production-ready applications. Whether you're preparing for interviews or refreshing your knowledge, this guide covers the 20 most important Spring Boot questions with simple, practical answers.

1. What is Spring Boot?

Spring Boot is a Java-based framework that lets you create stand-alone, production-grade applications quickly with minimal configuration.

2. What are the key features of Spring Boot?

Auto-configuration based on dependencies
Embedded servers (Tomcat, Jetty)
Production-ready tools like Actuator
No need for XML configuration
Project scaffolding using Spring Initializr

3. What is `@SpringBootApplication`?

It combines:

@Configuration – Declares configuration
@EnableAutoConfiguration – Enables auto-configuration
@ComponentScan – Scans packages for components

4. What is a Spring Bean?

A Bean is an object managed by Spring. Spring creates, configures, and injects beans into your app automatically.

5. What is Auto-Configuration?

Spring Boot configures your app based on the libraries present in the classpath. For example, adding spring-boot-starter-web sets up a web server and MVC config.

6. What is Dependency Injection?

It's a design pattern where Spring automatically provides a class with the objects it needs instead of the class creating them.

7. What is Spring Boot Actuator?

It provides endpoints to monitor and manage your app in production:

/actuator/health
/actuator/metrics
/actuator/info

8. What is a Circular Dependency?

Occurs when two or more beans depend on each other in a cycle. Spring fails to resolve it and throws an exception.

9. What is `@Qualifier`?

When multiple beans exist of the same type, use @Qualifier to specify which one to inject.

@Autowired
@Qualifier("myServiceImpl")
private MyService service;

10. What is `@RequestMapping`?

Used to map HTTP requests to controller methods. Variants like @GetMapping, @PostMapping make this more specific and easier to use.

11. What are the types of Bean Scopes?

singleton – One instance per Spring container (default)
prototype – A new instance every time it’s requested
request – One instance per HTTP request
session – One instance per HTTP session
application – One instance per ServletContext

12. How does Spring Boot handle REST communication?

RestTemplate – Traditional synchronous HTTP client. Easy to use and widely adopted, but being replaced in modern applications.
WebClient – Non-blocking, reactive HTTP client. Preferred for scalable and asynchronous systems.
RestClient – Introduced in Spring Boot 3. A simplified and fluent alternative to RestTemplate, designed for clean and type-safe REST calls.

13. What is the Spring Boot Starter Dependency?

Spring Boot starters are a set of convenient dependency descriptors you can include in your project. They simplify build configuration by bundling commonly used libraries.

Examples:

spring-boot-starter-web – for building RESTful APIs
spring-boot-starter-data-jpa – for database access using JPA
spring-boot-starter-security – for authentication and authorization

14. What is the difference between `@Component`, `@Service`, `@Repository`, and `@Controller`?

These annotations mark classes as Spring-managed beans and define their roles:

@Component – Generic stereotype for any Spring-managed component
@Service – Marks a service class (used for business logic)
@Repository – Indicates a DAO class and adds exception translation
@Controller – Used for web controllers to handle HTTP requests

15. How do you handle exceptions globally?

Use @ControllerAdvice and @ExceptionHandler:


java
@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(Exception.class)
    public ResponseEntity<String> handle(Exception e) {
        return ResponseEntity.status(500).body(e.getMessage());
    }
}

🐳 Docker Cheatsheet: Essential Commands for Every Developer

Jitendra Rawat — Thu, 01 May 2025 15:23:04 +0000

🚀 Introduction

Docker has transformed the way we develop, ship, and deploy applications by providing consistent environments across development, testing, and production. Whether you're just starting out or need a refresher, this Docker CLI cheatsheet covers the most essential commands every developer should know.

🔧 Getting Started

📦 Build a Docker Image

docker build -t <image_name> .

🔥 Build Without Cache

docker build -t <image_name> . --no-cache

📂 List Local Images

docker images

🧹 Remove an Image

docker rmi <image_name>

🧼 Prune Unused Images

docker image prune

🔐 Docker Hub & Authentication

🔑 Login to Docker Hub

docker login -u <username>

🚀 Push Image to Docker Hub

docker push <username>/<image_name>

🔍 Search for Images

docker search <image_name>

📥 Pull an Image

docker pull <image_name>

🧪 Working with Containers

🚀 Run a Container

docker run --name <container_name> <image_name>

🌐 Run with Port Mapping

docker run -p <host_port>:<container_port> <image_name>

🕶 Run in Background (Detached Mode)

docker run -d <image_name>

▶️ Start / ⏹ Stop Container

docker start <container_name>
docker stop <container_name>

🗑 Remove Stopped Container

docker rm <container_name>

🖥 Access Running Container

docker exec -it <container_name> sh

📈 Logs, Stats & Monitoring

📄 View Logs

docker logs -f <container_name>

🔎 Inspect Container Details

docker inspect <container_name>

📋 List Running Containers

docker ps

📋 List All Containers

docker ps -a

📊 Monitor Usage Stats

docker container stats

⚙️ Miscellaneous & System Info

🐳 Start Docker Daemon

docker -d

📘 Get Help on Any Command

docker --help

ℹ️ Show Docker System Info

docker info

🔗 Connect with me:

💼 LinkedIn

💻 GitHub

🧠 Master Git: A Practical Cheatsheet for Developers

Jitendra Rawat — Thu, 01 May 2025 14:11:12 +0000

Introduction: Whether you're a solo developer or collaborating with a team, version control is non-negotiable—and Git is the standard. It helps manage code changes, track history, experiment safely, and work across branches. But let’s be honest: Git's power can be overwhelming at first. That’s why I’ve compiled this concise, no-fluff Git cheatsheet to help you get up to speed quickly and stay productive.

🚀 Getting Started

🔧 Initialize a Repository

git init

Begin tracking a project in your current directory. This sets up a hidden .git folder.

📅 Clone an Existing Repo

git clone <repo-url>

Download a copy of a remote repository to your local machine.

📝 Tracking and Saving Changes

➕ Stage Files

git add <file>
git add .

Mark files to be included in the next commit.

✅ Commit Changes

git commit -m "your message"

Save a snapshot of staged changes with a message.

🔍 View Status

git status

Check what’s staged, modified, or untracked.

📊 View Differences

git diff        # unstaged vs working directory  
git diff --cached  # staged vs last commit

🌿 Branching & Merging

🌱 Create a Branch

git branch <branch-name>

📍 Switch Branches

git checkout <branch-name>
git checkout -b <new-branch>

🔀 Merge Branches

git merge <branch-name>

☁️ Working with Remotes

📄 Push Changes

git push origin <branch>

📅 Pull Updates

git pull origin <branch>

📜 View History

git log

💠 Advanced Commands

⏪ Revert a Commit

git revert <commit-hash>

Safely undo a commit without rewriting history.

🔀 Reset Commits

git reset --soft HEAD~1  
git reset --mixed HEAD~1  
git reset --hard HEAD~1

Control whether to keep, unstage, or discard changes when going back.

📦 Stash Your Work

git stash
git stash apply

Temporarily save your changes and come back to them later.

🍒 Cherry Pick Commits

git cherry-pick <commit-hash>

Apply a specific commit from one branch onto another.

💪 Rebase Branches

git rebase <branch>

Reapply commits from one branch on top of another for a cleaner history.

⚙️ Productivity Boosters

⚓ Git Hooks

Automate tasks before/after Git events by placing scripts in .git/hooks.

⚡ Create Aliases

git config --global alias.co checkout
git config --global alias.br branch

📚 Popular Git Workflows

Centralized Workflow: Direct commits to main
Feature Branch Workflow: Isolated branches per feature
Gitflow: Structured with main, develop, release, and feature branches