💸 Expense Splitter Backend

Backend REST API for Expense Splitter, a full-stack application inspired by Splitwise that helps users manage shared expenses, calculate balances, and simplify settlements within groups.

---

🚀 Live API

Backend

https://expense-splitter-backend-eb7u.onrender.com/

Swagger API Documentation

https://expense-splitter-backend-eb7u.onrender.com/swagger-ui/index.html

---

✨ Features

🔐 Authentication

• User Registration
• User Login
• JWT Authentication
• Password Encryption using BCrypt
• Protected APIs with Spring Security

👥 Group Management

• Create Group
• View Groups
• Delete Group
• Soft Delete Support

👤 Member Management

• Add Members
• Remove Members
• Group Membership Validation

💸 Expense Management

• Add Expense
• Delete Expense
• Equal Split
• Exact Split
• Input Validation

💰 Balance Management

• Calculate Group Balances
• Calculate User Balances
• Settlement Suggestions
• Optimized Debt Simplification

🛡 Exception Handling

• Global Exception Handler
• Consistent API Response Structure
• Validation Error Handling

---

🛠 Tech Stack

• Java 21
• Spring Boot
• Spring Security
• Spring Data JPA
• Hibernate
• JWT
• Maven
• TiDB Cloud (MySQL Compatible)
• Docker
• Render

---

🏗 Project Architecture

Controller
      │
      ▼
Service Layer
      │
      ▼
Repository Layer
      │
      ▼
Database (TiDB Cloud)

Project follows a layered architecture for better maintainability and separation of concerns.

---

📂 Project Structure

src
└── main
    ├── controller
    ├── service
    ├── repository
    ├── entity
    ├── dto
    ├── security
    ├── config
    ├── exception
    └── ExpenseSplitterApplication

---

🔐 Authentication APIs

Method	Endpoint	Description
POST	/auth/signup	Register User
POST	/auth/login	Login User

---

📁 Group APIs

Method	Endpoint
GET	/groups
POST	/groups
GET	/groups/{id}
DELETE	/groups/{id}

---

👥 Member APIs

Method	Endpoint
POST	/groups/{groupId}/members/{userId}
DELETE	/groups/{groupId}/members/{userId}
GET	/groups/members/{groupId}

---

💸 Expense APIs

Method	Endpoint
POST	/expenses/groups/{groupId}/expenses
GET	/expenses/groups/{groupId}/expenses
DELETE	/expenses/{expenseId}

---

💰 Balance APIs

Method	Endpoint
GET	/balances/groups/{groupId}/balances
GET	/balances/groups/{groupId}/settlements
GET	/balances/me

---

🔑 Environment Variables

Create an .env (or configure environment variables in your deployment platform):

DB_URL=
DB_USERNAME=
DB_PASSWORD=
JWT_SECRET=

---

⚙ Running Locally

Clone Repository

git clone https://github.com/DevbBhatt/expense-splitter-backend.git

Move into project

cd expense-splitter-backend

Run

./mvnw spring-boot:run

---

🐳 Docker

Build

docker build -t expense-splitter-backend .

Run

docker run -p 8080:8080 expense-splitter-backend

---

🌐 Deployment

Service	Platform
Backend	Render
Database	TiDB Cloud

---

🚀 Future Improvements

• Email Verification
• Password Reset
• Recurring Expenses
• Expense Categories
• Notifications
• File Attachments
• Group Invitations
• Audit Logs

---

👨‍💻 Author

Dev Bhatt

GitHub

https://github.com/DevbBhatt

LinkedIn

https://www.linkedin.com/in/dev-bhatt-9825b12bb/

---

⭐ If you like this project, consider giving it a star!