Spring Boot From Zero - Step-by-Step Guide

Learn Spring Boot by building a Product CRUD REST API from scratch.

What You'll Build

A REST API that can:

• GET all products from the database
• GET a single product by ID
• POST (create) a new product
• DELETE a product

Prerequisites

Before you start, make sure you have:

1. JDK 17 — Download OpenJDK 17

   • After installing, verify: java -version → should show 17.x
   • Set JAVA_HOME environment variable to your JDK path

2. IntelliJ IDEA — Download Community Edition (free)

   • Install the Lombok plugin: File → Settings → Plugins → search "Lombok" → Install
   • Enable annotation processing: File → Settings → Build → Compiler → Annotation Processors → ✅ Enable

3. MySQL — Running on localhost:3306

   • Create the database:

     CREATEDATABASEdemo_db;

4. Maven — Comes bundled with IntelliJ (no separate install needed)

How to Follow This Tutorial

Each commit in this repository is one step. Run git log --oneline to see all steps:

Step 8 - Exception handling & seed data
Step 7 - Controller: REST endpoints for Product CRUD
Step 6 - ServiceImpl: business logic + entity-DTO mapping
Step 5 - Service: define ProductService interface
Step 4 - DTO: create ProductDTO
Step 3 - Repository: ProductRepository with Spring Data JPA
Step 2 - Entity: Product domain model with JPA
Step 1 - Project setup: Spring Boot skeleton with Maven & MySQL

To see what changed in each step:

git log --oneline # see all steps
git show <commit-hash># see what files changed in that step
git diff <hash1><hash2># compare two steps

How to Run

mvn spring-boot:run

App starts at: http://localhost:8080

Test the API

Once the app is running, test these endpoints using curl or Postman:

Get all products

curl http://localhost:8080/api/products

Response: JSON array of all products (3 seed products from data.sql)

Get product by ID

curl http://localhost:8080/api/products/1

Response: Single product JSON object

Create a new product

curl -X POST http://localhost:8080/api/products \
-H "Content-Type: application/json" \
-d '{"name":"Galaxy S24","description":"Samsung flagship phone","price":899.99}'

Response: HTTP 201 + created product with generated ID

Delete a product

curl -X DELETE http://localhost:8080/api/products/1

Response: HTTP 204 No Content (success, no body)

Get a product that doesn't exist (error handling)

curl http://localhost:8080/api/products/999

Response: HTTP 404 + {"status":404, "error":"Not Found", "message":"Product not found with id 999"}

Project Structure

src/main/java/com/example/springbootfromzero/
├── SpringbootFromZeroApplication.java ← Entry point (Step 1)
├── domain/
│ └── Product.java ← JPA Entity - maps to DB table (Step 2)
├── repository/
│ └── ProductRepository.java ← Database access layer (Step 3)
├── dto/
│ └── ProductDTO.java ← API response shape (Step 4)
├── service/
│ ├── ProductService.java ← Business logic interface (Step 5)
│ └── impl/
│ └── ProductServiceImpl.java ← Business logic implementation (Step 6)
├── controller/
│ └── ProductController.java ← REST endpoints (Step 7)
└── exception/
├── ResourceNotFoundException.java ← Custom 404 exception (Step 6)
└── GlobalExceptionHandler.java ← Global error handling (Step 8)

Architecture (Request Flow)

Client (Browser/Postman/curl)
↓ HTTP Request (GET /api/products)
Controller (ProductController)
↓ calls service method
Service (ProductServiceImpl)
↓ calls repository method
Repository (ProductRepository)
↓ JPA generates SQL
Database (MySQL)
↑ returns rows
Repository → Entity (Product)
↑ returns entity
Service → converts to DTO (ProductDTO)
↑ returns DTO
Controller → wraps in ResponseEntity
↑ HTTP Response (JSON)
Client receives JSON

Next Steps (What to Learn After This)

1. Validation — Add @Valid, @NotNull, @Size to validate input
2. Update endpoint — Add PUT /api/products/{id} to update a product
3. Pagination — Use Pageable for large datasets
4. Model mapping — Use MapStruct instead of manual entity↔DTO conversion
5. Database migrations — Use Flyway or Liquibase instead of ddl-auto=update
6. Security — Add Spring Security for authentication
7. Testing — Write unit tests with @DataJpaTest and @SpringBootTest