Spring Boot User API

A versioned RESTful User Management API built with Spring Boot, demonstrating backend fundamentals and progressive real-world enhancements.

This project is intentionally developed in versions to reflect how production backend systems evolve over time.
Each version builds on the previous one while preserving clean architecture and REST best practices.

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🧩 Version 1 — In-Memory REST API

Version 1 focuses on core backend fundamentals without database persistence, emphasizing clean REST design and application structure.

V1 Highlights

• In-memory data storage using Java collections
• Full CRUD REST endpoints
• Proper HTTP status codes (200, 201, 400, 404, 204)
• Bean Validation with meaningful error messages
• Global exception handling
• Clean separation of Controller → Service → Model

Goal of V1: Demonstrate REST fundamentals and backend architecture without database complexity.

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🚀 Version 2 — Database Persistence (Spring Data JPA + H2)

Version 2 upgrades the API from an in-memory list to a real database-backed implementation using Spring Data JPA and an H2 in-memory database.

This version introduces persistence, automatic ID generation, and database verification while preserving the original API behavior.

✅ What’s New in V2

• Persistent storage using Spring Data JPA
• Auto-generated IDs with @GeneratedValue
• Entity mapping with @Entity and @Table
• Request validation using Bean Validation (@NotBlank, @Email)
• H2 Console enabled for database inspection
• Clean layered architecture:
  • Controller → Service → Repository

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▶ Run Locally (V1 or V2)

1. Run the application:

   • UserapiApplication

2. API Base URL:

   • http://localhost:8080

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🗄 H2 Console (V2)

• URL: http://localhost:8080/h2-console

Login Settings

• JDBC URL: jdbc:h2:mem:userdb
• Username: sa
• Password: (leave blank)

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🔥 API Endpoints (V1 & V2)

Method	Endpoint	Description	Status Codes
GET	/users	Get all users	200
GET	/users/{id}	Get user by ID	200, 404
POST	/users	Create a new user	201, 400
PUT	/users/{id}	Update existing user	200, 404
DELETE	/users/{id}	Delete user	204, 404

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📸 Proof — Version 2 Persistence

Create User (POST /users)

Database Verification (H2 Console)

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📸 API Examples — Version 1 (In-Memory)

These screenshots demonstrate the original in-memory implementation used in Version 1.

GET /users — 200 OK

POST /users — 201 Created

Validation Errors — 400 Bad Request

PUT /users/{id} — 200 OK

PUT /users/{id} — 404 Not Found

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🚀 Features

• Full CRUD operations
• Bean Validation with clear error responses
• Proper HTTP status codes
• Global exception handling
• Auto-generated user IDs
• Clean layered architecture
• Database persistence (V2)

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🛠 Tech Stack

• Java
• Spring Boot
• Spring Web
• Spring Data JPA
• H2 Database
• Jakarta Bean Validation
• Maven
• Postman

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🔜 Next Steps (Planned — V3)

• DTOs for request/response separation
• Pagination and sorting with Spring Data
• API documentation with Swagger / OpenAPI
• Optional PostgreSQL integration
• Basic authentication & authorization

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👤 Author

Ambrogio Bailey
Aspiring Backend Software Developer
Java • Spring Boot • REST APIs

GitHub: https://github.com/AmbrogioBailey
LinkedIn: https://www.linkedin.com/in/ambrogio-bailey-b67529373/