Getting Started with Spring Boot 3

Spring Boot is the most popular Java framework for building production-ready applications fast. With Spring Boot 3, you get native support for Java 17+, improved observability, and a cleaner architecture. Let's build a REST API from scratch.

1. Prerequisites

Before we start, make sure you have:

• Java 17 or higher installed
• Maven or Gradle
• IntelliJ IDEA or VS Code with Java extension

2. Create a Spring Boot Project

The easiest way is using Spring Initializr. Go to start.spring.io, select:

• Project: Maven
• Language: Java
• Spring Boot: 3.x.x
• Dependencies: Spring Web, Spring Data JPA, H2 Database

Click Generate and extract the ZIP. Your project structure will look like this:

text
my-app/
├── src/
│   ├── main/
│   │   ├── java/com/example/myapp/
│   │   │   └── MyAppApplication.java
│   │   └── resources/
│   │       └── application.properties
│   └── test/
└── pom.xml

3. Your First Controller

A controller handles HTTP requests. Let's create a simple one:

java
@RestController
@RequestMapping("/api/greet")
public class GreetController {

    @GetMapping
    public String greet() {
        return "Hello from Spring Boot 3!";
    }

    @GetMapping("/{name}")
    public String greetUser(@PathVariable String name) {
        return "Hello, " + name + "!";
    }
}

4. Creating a Model and Repository

Let's create a Product entity with JPA:

java
@Entity
public class Product {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;
    private double price;

    // Constructors, Getters & Setters
    public Product() {}

    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }

    // getters and setters...
}

Now create the repository — Spring Data JPA gives you CRUD for free:

java
public interface ProductRepository extends JpaRepository<Product, Long> {
    // That's it! Spring generates findAll, findById, save, delete automatically
    List<Product> findByName(String name); // custom query
}

5. Building the REST API

Wire up the service layer and controller:

java
@Service
public class ProductService {

    private final ProductRepository repo;

    public ProductService(ProductRepository repo) {
        this.repo = repo;
    }

    public List<Product> getAll() { return repo.findAll(); }
    public Product getById(Long id) { return repo.findById(id).orElseThrow(); }
    public Product create(Product p) { return repo.save(p); }
    public void delete(Long id) { repo.deleteById(id); }
}

@RestController
@RequestMapping("/api/products")
public class ProductController {

    private final ProductService service;

    public ProductController(ProductService service) {
        this.service = service;
    }

    @GetMapping
    public List<Product> getAll() { return service.getAll(); }

    @GetMapping("/{id}")
    public Product getById(@PathVariable Long id) { return service.getById(id); }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Product create(@RequestBody Product product) { return service.create(product); }

    @DeleteMapping("/{id}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void delete(@PathVariable Long id) { service.delete(id); }
}

6. application.properties Setup

properties
# H2 in-memory database (great for development)
spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driver-class-name=org.h2.Driver
spring.jpa.hibernate.ddl-auto=update
spring.h2.console.enabled=true
server.port=8080

7. Run and Test

Run the app with Maven:

bash
mvn spring-boot:run

Test your endpoints with curl or Postman:

bash
# Get all products
curl http://localhost:8080/api/products

# Create a product
curl -X POST http://localhost:8080/api/products \
  -H "Content-Type: application/json" \
  -d '{"name":"Laptop","price":999.99}'