🚀 Spring Boot CRUD API Demo

A comprehensive REST API demonstration project built with Spring Boot 3.x, showcasing full CRUD operations with modern Java enterprise technologies.

📋 Project Overview

This project serves as a technical validation and learning demonstration for Spring Boot API development, implementing a complete User management system with best practices.

🛠️ Tech Stack

Technology	Version	Purpose
Java	17 (LTS)	Programming Language
Spring Boot	3.5.6	Framework
Spring Data JPA	3.x	Data Access Layer
Jakarta EE	9+	Enterprise Specifications
Maven	3.9.11	Build Tool
MySQL	8.x	Database
Hibernate	6.x	ORM Framework

🏗️ Architecture

┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   Controller    │────│    Service      │────│   Repository    │
│   (REST API)    │    │ (Business Logic)│    │  (Data Access)  │
└─────────────────┘    └─────────────────┘    └─────────────────┘
         │                       │                       │
         │                       │                       │
┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   HTTP Client   │    │   Validation    │    │     MySQL       │
│   (Postman)     │    │   Error Handle  │    │   Database      │
└─────────────────┘    └─────────────────┘    └─────────────────┘

🎯 Features

✅ Complete CRUD Operations

• CREATE - Add new users with validation
• READ - Retrieve all users or specific user by ID
• UPDATE - Modify existing user information
• DELETE - Remove users from database

🛡️ Advanced Features

• Input Validation - Username and email validation
• Duplicate Prevention - Username uniqueness check
• Error Handling - Comprehensive exception management
• HTTP Status Codes - Proper REST API responses
• Service Layer - Business logic separation

📡 API Endpoints

Method	Endpoint	Description	Response
GET	/users	Get all users	200 OK
GET	/users/{id}	Get user by ID	200 OK / 404 Not Found
POST	/users	Create new user	200 OK / 400 Bad Request
PUT	/users/{id}	Update user	200 OK / 404 Not Found
DELETE	/users/{id}	Delete user	200 OK / 404 Not Found

📝 Request/Response Examples

Create User (POST /users)

{
    "username": "john_doe",
    "name": "John Doe",
    "email": "john@example.com"
}

Response

"User created successfully with ID: 1"

🚀 Quick Start

Prerequisites

• Java 17+ installed
• Maven 3.6+ installed
• MySQL 8.x running
• Git installed

1. Clone Repository

git clone https://github.com/YOUR_USERNAME/spring-boot-crud-api-demo.git
cd spring-boot-crud-api-demo

2. Database Setup

CREATE DATABASE crash_api_course;

3. Configuration

Update src/main/resources/application.properties:

spring.datasource.url=jdbc:mysql://localhost:3306/crash_api_course
spring.datasource.username=YOUR_USERNAME
spring.datasource.password=YOUR_PASSWORD

4. Run Application

# Using Maven Wrapper (Recommended)
./mvnw spring-boot:run

# Using installed Maven
mvn spring-boot:run

5. Test API

Application will start on http://localhost:8080

🧪 Testing with Postman

Import Collection

1. Open Postman
2. Import the following collection:

{
    "info": { "name": "Spring Boot CRUD API" },
    "variable": [{ "key": "baseUrl", "value": "http://localhost:8080" }],
    "item": [
        {
            "name": "Get All Users",
            "request": { "method": "GET", "url": "{{baseUrl}}/users" }
        },
        {
            "name": "Create User",
            "request": {
                "method": "POST",
                "url": "{{baseUrl}}/users",
                "header": [{ "key": "Content-Type", "value": "application/json" }],
                "body": {
                    "mode": "raw",
                    "raw": "{\"username\":\"alice\",\"name\":\"Alice Smith\",\"email\":\"alice@example.com\"}"
                }
            }
        }
    ]
}

📁 Project Structure

src/
├── main/
│   ├── java/com/saturn/crash_api_course/
│   │   ├── CrashApiCourseApplication.java     # Main Application
│   │   ├── controller/
│   │   │   └── UserController.java            # REST Controllers
│   │   ├── service/
│   │   │   └── UserService.java               # Business Logic
│   │   ├── repository/
│   │   │   └── UserRepository.java            # Data Access
│   │   └── model/
│   │       └── User.java                      # JPA Entities
│   └── resources/
│       └── application.properties             # Configuration
└── test/
    └── java/
        └── CrashApiCourseApplicationTests.java # Tests

🔍 Learning Objectives

This project demonstrates:

• ✅ Spring Boot 3.x modern features
• ✅ RESTful API design principles
• ✅ 3-Layer Architecture (Controller-Service-Repository)
• ✅ JPA/Hibernate ORM usage
• ✅ Dependency Injection patterns
• ✅ Input Validation best practices
• ✅ Error Handling strategies
• ✅ HTTP Status Codes proper usage
• ✅ Maven build management

🛠️ Development Tips

Database Connection Test

mysql -u root -p -e "SELECT 1;"

Check Application Logs

tail -f logs/spring-boot-application.log

Maven Commands

# Clean and compile
./mvnw clean compile

# Run tests
./mvnw test

# Package JAR
./mvnw clean package