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Learn Spring-boot - 9 Code Examples & CST Typing Practice Test

Spring Boot is a Java-based framework that simplifies building production-ready Spring applications. It provides convention-over-configuration, embedded servers, and production-grade features for microservices and web applications.

View all 9 Spring-boot code examples →
Spring Boot Simple Counter APISpring Boot Hello World APISpring Boot JSON EchoSpring Boot Query Param ExampleSpring Boot Path Variable ExampleSpring Boot Async Endpoint ExampleSpring Boot Custom 404 ResponseSpring Boot Combined Routes ExampleSpring Boot Health Check Endpoint

Learn SPRING-BOOT with Real Code Examples

Updated Nov 25, 2025

Explain

Spring Boot allows developers to create stand-alone, production-ready Spring applications quickly.

It provides embedded servers like Tomcat, Jetty, or Undertow, removing deployment complexity.

Supports auto-configuration to reduce boilerplate code.

Integrates seamlessly with Spring ecosystem: Spring Data, Spring Security, Spring MVC, etc.

Widely used for microservices, REST APIs, and enterprise-grade backend systems.

Core Features

Dependency injection and inversion-of-control via Spring Core

Auto-configuration based on classpath and beans

Embedded server (Tomcat, Jetty, Undertow)

Spring MVC for web and REST endpoints

Spring Data integration for ORM and database access

Basic Concepts Overview

Spring Boot application instance - entry point class

Controllers - define REST endpoints

Services - business logic layer

Repositories - data access layer with Spring Data

Beans - managed objects via dependency injection

Project Structure

src/main/java/ - main application code

src/main/resources/ - configuration files, static assets, templates

controllers/ - REST controllers

services/ - business logic classes

repositories/ - database access interfaces

Building Workflow

Create Spring Boot project using Spring Initializr

Define REST controllers with `@RestController`

Implement business logic in service classes

Configure data access with Spring Data repositories

Run application using embedded server

Difficulty Use Cases

Beginner: simple REST endpoints

Intermediate: CRUD API with database integration

Advanced: authentication and authorization

Expert: microservices with service discovery

Auditor: monitor performance and optimize metrics

Comparisons

Spring Boot vs Spring MVC: Boot adds auto-configuration and embedded server

Spring Boot vs Flask: Java enterprise ecosystem vs Python lightweight

Spring Boot vs FastAPI: Spring Boot is Java, FastAPI is Python with async support

Spring Boot vs Express.js: Full-featured vs minimal Node.js framework

Spring Boot vs Micronaut: Boot is mature, Micronaut optimized for startup and memory

Versioning Timeline

2014 - Spring Boot initial release

2015 - Spring Boot 1.2 with Actuator and DevTools

2016-2018 - Spring Boot 2.x with reactive support

2019-2021 - Cloud-native and Kubernetes integration

2022-2025 - Enhanced performance, security, and observability

Glossary

Spring Boot application - entry point class with `@SpringBootApplication`

Controller - REST endpoints handler

Service - business logic class

Repository - interface for database access

Bean - managed object in Spring context

Installation Setup

Install JDK 17+

Set up Maven or Gradle project

Add Spring Boot starter dependencies

Create main application class annotated with `@SpringBootApplication`

Run with `mvn spring-boot:run` or IDE run configuration

Environment Setup

Install JDK 17+

Install Maven or Gradle

Set up IDE (IntelliJ, Eclipse, VSCode)

Create Spring Boot project via Initializr

Verify server starts locally

Config Files

pom.xml / build.gradle - dependencies

application.properties / application.yml - config

MainApplication.java - entry point class

controllers/ - REST controllers

services/ - business logic classes

Cli Commands

spring init -> create project using Spring CLI

mvn spring-boot:run -> run app with Maven

gradle bootRun -> run app with Gradle

java -jar target/app.jar -> run packaged JAR

mvn clean package -> build production JAR

Internationalization

Spring MessageSource for i18n

UTF-8 encoding by default

Locale-specific messages and templates

Integration with translation libraries

Supports multi-language enterprise apps

Accessibility

Accessible via HTTP/S clients

Supports CORS configuration

Works on all platforms with JVM

Middleware (filters/interceptors) ensures security

Internationalization supported via MessageSource

Ui Styling

Spring Boot primarily backend

Serve static files via `resources/static`

Integrate with frontend frameworks (React, Angular, Vue)

Render templates with Thymeleaf or FreeMarker

Provide JSON APIs for SPA/frontend apps

State Management

Stateless REST endpoints by default

Session management via Spring Security

Persistent state via database/repositories

Cache with Spring Cache or Redis

Application context holds beans and configuration

Data Management

Parse JSON requests/responses

Validate inputs via Bean Validation (JSR 380)

Connect to SQL/NoSQL databases via Spring Data

Cache frequently accessed data

Log and monitor data access operations

Architecture

Layered architecture (Controller-Service-Repository)

Embedded servlet container

Dependency injection for components

Auto-configuration based on classpath

Integration with Spring ecosystem modules

Rendering Model

Client sends HTTP request -> Spring Boot embedded server

DispatcherServlet routes request to controller

Controller processes request and calls service layer

Service interacts with repository/database

Response sent back to client

Architectural Patterns

Layered architecture (Controller-Service-Repository)

Dependency injection and Inversion-of-Control

Auto-configuration for environment detection

Embedded servlet container

Integration with Spring modules and extensions

Real World Architectures

REST APIs for web/mobile apps

Microservices with Spring Cloud

Enterprise backend for banking/finance

Authentication and authorization services

Cloud-native applications with Kubernetes

Design Principles

Convention-over-configuration

Rapid development with auto-configuration

Embedded servers for standalone deployment

Integration-friendly with Spring ecosystem

Production-ready defaults (metrics, monitoring, logging)

Scalability Guide

Deploy multiple instances behind load balancer

Use caching for database queries

Horizontal scaling with microservices

Monitor performance via Actuator

Optimize startup with lazy initialization

Migration Guide

Adapt from Spring MVC to Boot by adding `@SpringBootApplication`

Use Spring Boot starters for dependencies

Configure properties in `application.yml` or `.properties`

Refactor controllers, services, repositories

Test endpoints and database integration

Performance Notes

Embedded server allows fast local testing

Auto-configuration reduces boilerplate and latency

Can scale horizontally with microservices

Spring Boot Actuator provides performance metrics

Lazy initialization can improve startup time

Security Notes

Use Spring Security for authentication/authorization

Use HTTPS in production

Sanitize inputs and use validation

Implement CSRF protection for web apps

Keep dependencies updated for vulnerabilities

Monitoring Analytics

Spring Boot Actuator for metrics

Monitor memory and CPU

Log requests and errors

Integrate with Prometheus/Grafana

Profile endpoints for high traffic

Code Quality

Follow Java coding standards

Write unit/integration tests with JUnit and Mockito

Document REST endpoints and services

Use dependency injection cleanly

Monitor and profile performance

Practical Examples

REST API for e-commerce

User authentication and authorization service

Microservices backend with Eureka and Ribbon

Data processing service with Spring Batch

Monitoring and logging service with Actuator

Troubleshooting

Ensure compatible JDK and Spring Boot version

Check dependency conflicts in Maven/Gradle

Verify annotations (`@RestController`, `@Service`, `@Repository`)

Monitor logs for startup errors

Validate database connectivity

Testing Guide

Use JUnit and Mockito for unit testing

Spring Boot Test for integration testing

Test REST endpoints with Postman

Use Testcontainers for database tests

Automate tests in CI/CD pipelines

Deployment Options

Standalone JAR deployment with embedded server

Cloud platforms: AWS, Azure, GCP

Docker containerization

Kubernetes for microservices

CI/CD pipelines for automated deployment

Tools Ecosystem

Spring Initializr

Maven/Gradle build tools

Spring Boot CLI

Actuator for monitoring

Spring Boot DevTools for development

Integrations

Databases: MySQL, PostgreSQL, MongoDB

Messaging: Kafka, RabbitMQ

Caching: Redis, Ehcache

Spring Security for authentication

Frontend frameworks: Angular, React, Vue

Productivity Tips

Use Spring Boot starters to simplify dependencies

Leverage auto-configuration to reduce boilerplate

Use embedded servers for quick testing

Automate tests and deployments

Monitor metrics and logs proactively

Challenges

Mastering Spring Boot auto-configuration

Managing dependency injection and bean scopes

Optimizing startup time and memory usage

Implementing scalable microservices architecture

Securing APIs and enterprise applications

Learning Path

Learn Java basics

Understand Spring Core and dependency injection

Learn Spring Boot auto-configuration

Build REST APIs with Spring MVC

Deploy Spring Boot applications

Skill Improvement Plan

Week 1: Java fundamentals

Week 2: Spring Core and Boot basics

Week 3: REST APIs and database integration

Week 4: Security and microservices

Week 5: Deployment and monitoring

Interview Questions

What is Spring Boot and why use it?

Explain auto-configuration in Spring Boot

How does Spring Boot differ from Spring MVC?

How do you implement REST endpoints?

How to secure a Spring Boot application?

Cheat Sheet

@SpringBootApplication -> main class annotation

SpringApplication.run(App.class, args) -> start app

@RestController -> define REST endpoints

@Service -> business logic layer

@Repository -> data access layer

Books

Spring Boot in Action

Spring Microservices in Action

Pro Spring Boot

Learning Spring Boot 3.0

Spring Boot: Up and Running

Tutorials

Getting started with Spring Boot

Build REST APIs with Spring Boot

Integrate databases and JPA

Secure applications with Spring Security

Deploy Spring Boot app to production

Official Docs

https://spring.io/projects/spring-boot

https://github.com/spring-projects/spring-boot

Community Links

Spring Boot GitHub

StackOverflow Spring Boot questions

Reddit r/spring

Spring community forums

YouTube Spring Boot tutorials

Community Support

Spring Boot GitHub

StackOverflow Spring Boot questions

Spring community forums

Reddit r/spring

Official documentation and guides

Monetization

Backend for SaaS platforms

Enterprise application development

API-as-a-service offerings

E-commerce backend systems

Cloud-native microservices

Future Roadmap

Enhanced reactive programming support

Improved performance and startup time

Better cloud-native integration

Extended observability and metrics

Community-driven feature improvements

When Not To Use

Very small scripts or microservices requiring minimal footprint

Projects needing very fast startup with low memory

Teams unfamiliar with Java/Spring ecosystem

Applications not requiring enterprise features

Prototypes needing rapid experimentation with lightweight tools

Final Summary

Spring Boot simplifies building production-ready Spring applications.

Supports embedded servers and auto-configuration.

Integrates with the Spring ecosystem for enterprise features.

Ideal for microservices, REST APIs, and scalable backends.

Widely adopted in enterprise and cloud-native applications.

Faq

Is Spring Boot free?

Yes - open-source under Apache 2.0 license.

Can Spring Boot create standalone apps?

Yes - with embedded Tomcat/Jetty/Undertow.

Is Spring Boot suitable for production?

Yes - widely used in enterprise-grade applications.

Does Spring Boot include ORM?

It integrates with Spring Data and JPA for ORM.

How does Spring Boot compare to Flask?

Spring Boot is Java/enterprise-focused; Flask is Python/lightweight.

Code Sample Descriptions

1

Spring Boot Simple Counter API

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;

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

@RestController
@RequestMapping("/counter")
class CounterController {
    private int count = 0;

    @GetMapping
    public int getCount() {
        return count;
    }

    @PostMapping("/increment")
    public int increment() {
        return ++count;
    }

    @PostMapping("/decrement")
    public int decrement() {
        return --count;
    }

    @PostMapping("/reset")
    public int reset() {
        count = 0;
        return count;
    }
}

Demonstrates a simple Spring Boot REST API with a counter using a Controller and in-memory state.

Let’s Try →
2

Spring Boot Hello World API

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;

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

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

A minimal Spring Boot API returning 'Hello World'.

Let’s Try →
3

Spring Boot JSON Echo

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;
import java.util.Map;

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

@RestController
class EchoController {
    @PostMapping("/echo")
    public Map<String, Object> echo(@RequestBody Map<String, Object> payload) {
        return payload;
    }
}

Echoes back JSON sent in POST request.

Let’s Try →
4

Spring Boot Query Param Example

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;

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

@RestController
class GreetController {
    @GetMapping("/greet")
    public String greet(@RequestParam(defaultValue="Guest") String name) {
        return "Hello " + name;
    }
}

Greets user using query parameters.

Let’s Try →
5

Spring Boot Path Variable Example

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;

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

@RestController
@RequestMapping("/users")
class UserController {
    @GetMapping("/{id}")
    public String getUser(@PathVariable int id) {
        return "User " + id;
    }
}

Returns info for a user based on path variable.

Let’s Try →
6

Spring Boot Async Endpoint Example

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;
import java.util.concurrent.CompletableFuture;

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

@RestController
class AsyncController {
    @GetMapping("/async")
    public CompletableFuture<String> asyncHello() {
        return CompletableFuture.supplyAsync(() -> {
        try { Thread.sleep(1000); } catch (InterruptedException e) {}
        return "Async Hello";
        });
    }
}

Asynchronous endpoint returning a delayed response.

Let’s Try →
7

Spring Boot Custom 404 Response

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.NoHandlerFoundException;

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

@RestController
@ControllerAdvice
class ErrorController {
    @ExceptionHandler(NoHandlerFoundException.class)
    @ResponseStatus(HttpStatus.NOT_FOUND)
    public String handle404() {
        return "Custom 404 Not Found";
    }
}

Custom error handling for 404 requests.

Let’s Try →
8

Spring Boot Combined Routes Example

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;
import java.util.Map;

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

@RestController
class CombinedController {
    private int count = 0;

    @GetMapping("/counter")
    public int getCount() { return count; }
    @PostMapping("/counter/increment")
    public int increment() { return ++count; }
    @PostMapping("/counter/decrement")
    public int decrement() { return --count; }
    @PostMapping("/counter/reset")
    public int reset() { return count = 0; }

    @PostMapping("/echo")
    public Map<String, Object> echo(@RequestBody Map<String, Object> payload) { return payload; }

    @GetMapping("/greet")
    public String greet(@RequestParam(defaultValue="Guest") String name) { return "Hello " + name; }
}

Multiple endpoints: counter, echo, and greeting combined.

Let’s Try →
9

Spring Boot Health Check Endpoint

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;

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

@RestController
class HealthController {
    @GetMapping("/health")
    public String health() { return "OK"; }
}

Simple health check endpoint returning status.

Let’s Try →

Frequently Asked Questions about Spring-boot

What is Spring-boot?

Spring Boot is a Java-based framework that simplifies building production-ready Spring applications. It provides convention-over-configuration, embedded servers, and production-grade features for microservices and web applications.

What are the primary use cases for Spring-boot?

RESTful API development. Microservices architecture. Enterprise backend systems. Web applications with Spring MVC. Integration with databases and messaging systems

What are the strengths of Spring-boot?

Rapid development with minimal configuration. Extensive ecosystem and community support. Enterprise-grade, scalable architecture. Embedded server simplifies deployment. Rich production features (metrics, monitoring, health checks)

What are the limitations of Spring-boot?

Heavier than micro-frameworks for very small apps. Startup time longer than lightweight frameworks. Learning curve for Spring ecosystem concepts. Overhead if many auto-configurations are unused. Can feel complex for simple projects

How can I practice Spring-boot typing speed?

CodeSpeedTest offers 9+ real Spring-boot code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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