Creating REST APIs using Spring Boot

June 24, 2025

Creating REST APIs Using Spring Boot

Spring Boot is a popular framework for building production-ready REST APIs in Java with minimal setup. It simplifies the development process by providing auto-configuration and a variety of tools to quickly build robust backend applications.

✅ Prerequisites

Java 17+ installed

Maven or Gradle installed

IDE (e.g., IntelliJ IDEA, Eclipse, VS Code)

Spring Boot CLI (optional)

1. Create a Spring Boot Project

You can use Spring Initializr to generate a project:

🔧 Choose:

Project: Maven or Gradle

Language: Java

Spring Boot version: (latest stable)

Dependencies:

Spring Web

Spring Boot DevTools (optional)

Spring Data JPA (if using a database)

H2 Database (for quick testing)

Click Generate, then unzip and open the project in your IDE.

2. Define a Model Class

Create a simple class to represent your data.

java

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// src/main/java/com/example/demo/model/Product.java

package com.example.demo.model;

public class Product {

private Long id;

private String name;

private double price;

// Getters and setters

}

3. Create a REST Controller

Define endpoints to handle HTTP requests.

java

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// src/main/java/com/example/demo/controller/ProductController.java

package com.example.demo.controller;

import com.example.demo.model.Product;

import org.springframework.web.bind.annotation.*;

import java.util.*;

@RestController

@RequestMapping("/api/products")

public class ProductController {

private Map<Long, Product> productDB = new HashMap<>();

private Long nextId = 1L;

@GetMapping

public List<Product> getAllProducts() {

return new ArrayList<>(productDB.values());

}

@GetMapping("/{id}")

public Product getProductById(@PathVariable Long id) {

return productDB.get(id);

}

@PostMapping

public Product createProduct(@RequestBody Product product) {

product.setId(nextId++);

productDB.put(product.getId(), product);

return product;

}

@PutMapping("/{id}")

public Product updateProduct(@PathVariable Long id, @RequestBody Product updatedProduct) {

updatedProduct.setId(id);

productDB.put(id, updatedProduct);

return updatedProduct;

}

@DeleteMapping("/{id}")

public String deleteProduct(@PathVariable Long id) {

productDB.remove(id);

return "Product deleted successfully";

}

4. Run the Application

In your IDE or using the command line:

bash

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./mvnw spring-boot:run

bash

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gradle bootRun

Default server port: http://localhost:8080

5. Test Your API

You can use tools like:

Postman

curl

httpie

Browser (for GET requests)

Example curl requests:

bash

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curl -X POST http://localhost:8080/api/products \

-H "Content-Type: application/json" \

-d '{"name":"Laptop", "price":999.99}'

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

6. (Optional) Use Spring Data JPA for Persistence

Add a JPA entity:

java

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@Entity

public class Product {

@Id @GeneratedValue

private Long id;

private String name;

private double price;

// getters and setters

}

Create a repository:

java

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public interface ProductRepository extends JpaRepository<Product, Long> {}

Update your controller:

java

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@RestController

@RequestMapping("/api/products")

public class ProductController {

@Autowired

private ProductRepository repo;

@GetMapping

public List<Product> getAll() { return repo.findAll(); }

@PostMapping

public Product create(@RequestBody Product product) { return repo.save(product); }

@PutMapping("/{id}")

public Product update(@PathVariable Long id, @RequestBody Product p) {

p.setId(id);

return repo.save(p);

}

@DeleteMapping("/{id}")

public void delete(@PathVariable Long id) { repo.deleteById(id); }

}

✅ Conclusion

With Spring Boot, creating REST APIs is simple and efficient. You can start with in-memory storage for learning, then scale to full database-backed APIs using JPA.

➕ Next Steps

Add input validation with @Valid

Secure your API with Spring Security + JWT

Add exception handling with @ControllerAdvice

Generate OpenAPI docs using Springdoc or Swagger

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