🚀 Spring Boot User CRUD REST API

RESTful CRUD Operations using Spring Boot | Java | Maven | UUID | Validation

A clean and well-structured RESTful API built with Spring Boot that performs complete CRUD operations on user data using in-memory storage, request validation, UUID identifiers, and layered architecture.

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📌 Project Overview

This project was developed as part of the Prodigy InfoTech Internship – Task 1: Build a REST API for CRUD Operations.

The application demonstrates the fundamentals of backend development by implementing a RESTful API capable of creating, retrieving, updating, and deleting user records.

The project follows a clean layered architecture (Controller → Service → DTO → Model) and uses HashMap as an in-memory data store, making it ideal for learning Spring Boot fundamentals before integrating a database.

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✨ Features

• ✅ Create User
• ✅ Retrieve All Users
• ✅ Retrieve User by ID
• ✅ Update Existing User
• ✅ Delete User
• ✅ UUID Generated for Every User
• ✅ In-Memory Storage using HashMap
• ✅ Request Validation
• ✅ Global Exception Handling
• ✅ Layered Architecture
• ✅ RESTful API Design
• ✅ Tested using Postman

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📸 Project Screenshots

🏗 Project Structure

Shows the layered package structure used in the application.

--- ## Tomcat Running

--- ## Create User

---

GET User

---

GET User BY id

---

Update User

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Delete User

---

Valid Email Request

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User not found

🛠 Tech Stack

Technology	Purpose
Java 21	Programming Language
Spring Boot	Backend Framework
Spring Web MVC	REST API Development
Maven	Dependency Management
Jakarta Bean Validation	Request Validation
UUID	Unique User Identifier
HashMap	In-Memory Storage
IntelliJ IDEA	Development Environment
Postman	API Testing

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🏗 Project Architecture

                 Client (Postman)

                        │
                        ▼

             ┌─────────────────────┐
             │   UserController     │
             └─────────────────────┘
                        │
                        ▼

             ┌─────────────────────┐
             │    UserService       │
             └─────────────────────┘
                        │
                        ▼

             ┌─────────────────────┐
             │ HashMap<UUID, User>  │
             └─────────────────────┘

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📂 Project Structure

basic-rest-api
│
├── src
│   ├── main
│   │   ├── java
│   │   │   └── com.example.basic_rest_api
│   │   │
│   │   ├── controller
│   │   │     └── UserController.java
│   │   │
│   │   ├── dto
│   │   │     └── UserRequest.java
│   │   │
│   │   ├── exception
│   │   │     ├── GlobalExceptionHandler.java
│   │   │     └── UserNotFoundException.java
│   │   │
│   │   ├── model
│   │   │     └── User.java
│   │   │
│   │   ├── service
│   │   │     └── UserService.java
│   │   │
│   │   └── BasicRestApiApplication.java
│   │
│   └── resources
│
├── pom.xml
├── README.md
└── .gitignore

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📦 Data Model

Each user contains the following fields:

Field	Type
id	UUID
name	String
email	String
age	Integer

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🔗 REST API Endpoints

Method	Endpoint	Description	Response
POST	/api/users	Create User	201 Created
GET	/api/users	Retrieve All Users	200 OK
GET	/api/users/{id}	Retrieve User by UUID	200 OK
PUT	/api/users/{id}	Update User	200 OK
DELETE	/api/users/{id}	Delete User	204 No Content

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🧪 Sample Request

Create User

POST /api/users

{
  "name": "Ritu Singh",
  "email": "ritu@example.com",
  "age": 24
}

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Successful Response

{
  "id": "81acc614-cae5-44a2-881e-d85156fa6efb",
  "name": "Ritu Singh",
  "email": "ritu@example.com",
  "age": 24
}

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⚠️ Validation & Error Handling

Scenario	Status Code
Invalid Request Body	400 Bad Request
Invalid Email	400 Bad Request
Missing Required Fields	400 Bad Request
User Not Found	404 Not Found

Example Error Response

{
  "error": "User not found with id: xxxxxxxxx"
}

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⚙️ How to Run the Project

Clone Repository

git clone https://github.com/uddishasinghh31/YOUR_REPOSITORY_NAME.git

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Open in IntelliJ IDEA

Import the project as a Maven Project and allow dependencies to download.

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Run the Application

Using Maven

mvn spring-boot:run

or simply run

BasicRestApiApplication.java

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The application starts at

http://localhost:8080

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📝 Notes

• Data is stored in memory using HashMap.
• Restarting the application clears all stored users.
• UUIDs are automatically generated for every new user.
• Input validation is handled using Jakarta Bean Validation annotations.

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🚀 Future Improvements

• MySQL Database Integration
• Spring Data JPA
• Hibernate ORM
• Flyway Database Migration
• Spring Security
• JWT Authentication
• Swagger/OpenAPI Documentation
• Docker Support
• Unit Testing with JUnit & Mockito
• Cloud Deployment (AWS / Railway / Render)

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👩‍💻 Author

Udisha Singh

Backend Developer | Java | Spring Boot | MySQL

• GitHub: https://github.com/uddishasinghh31
• LinkedIn: https://www.linkedin.com/in/udisha-singh-47170b338

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📄 Internship Details

Organization: Prodigy InfoTech

• Task 1: Build a REST API for CRUD Operations using Spring Boot
• Storage: In-Memory using HashMap
• Architecture: Controller → Service → DTO → Model

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