🚀 Expense Tracker Backend API

A production‑ready Spring Boot REST API for managing personal expenses with JWT authentication, PostgreSQL, validation, and Swagger docs.

Built step‑by‑step as a real‑world backend project.

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✨ Features

🔐 Authentication & Security

• User Registration
• Login with JWT token
• BCrypt password hashing
• JWT validation filter
• Protected APIs
• User‑specific data isolation

💼 Expense Management (CRUD)

• Add expense
• Get my expenses only
• Update expense
• Delete expense

🧠 Professional Practices

• Bean validation (@Valid)
• Global exception handling
• Clean error responses
• Swagger documentation
• Environment variable config
• Cloud ready (Render)

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🛠️ Tech Stack

Layer	Tech
Backend	Spring Boot 3
Security	Spring Security + JWT
Database	PostgreSQL
ORM	JPA / Hibernate
Build Tool	Maven
Docs	Swagger (springdoc-openapi)
Deployment	Render

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📂 Project Structure

src/main/java/com/expensetracker
 ├── controller
 ├── service
 ├── repository
 ├── entity
 ├── security
 ├── dto
 ├── exception
 └── ExpenseTrackerBackendApplication.java

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⚙️ Local Setup

1️⃣ Clone project

git clone <https://github.com/variables-dev-coder/expense-tracker-backend>
cd expense-tracker-backend

2️⃣ Start PostgreSQL

Create database:

expense_tracker

3️⃣ Configure properties

application.properties already supports local + cloud:

spring.datasource.url=${DB_URL:jdbc:postgresql://localhost:5432/expense_tracker}
spring.datasource.username=${DB_USERNAME:postgres}
spring.datasource.password=${DB_PASSWORD:root}

4️⃣ Run app

mvn spring-boot:run

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📖 API Documentation (Swagger)

After running:

http://localhost:8080/swagger-ui/index.html

Test all APIs directly in browser.

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🔑 Authentication Flow

Register

POST /api/auth/register

Login

POST /api/auth/login

Response:

{
  "token": "JWT_TOKEN"
}

Use token

Header:

Authorization: Bearer JWT_TOKEN

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📡 Main Endpoints

Method	Endpoint	Description
POST	/api/auth/register	Register user
POST	/api/auth/login	Login
GET	/api/expenses	Get my expenses
POST	/api/expenses	Add expense
PUT	/api/expenses/{id}	Update
DELETE	/api/expenses/{id}	Delete

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☁️ Deployment (Render)

Steps

1. Create PostgreSQL on Render
2. Create Web Service
3. Add environment variables:

DB_URL
DB_USERNAME
DB_PASSWORD

4. Deploy

Example:

https://expense-tracker-api.onrender.com

Swagger:

https://expense-tracker-api.onrender.com/swagger-ui/index.html

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🎯 Learning Outcomes

This project demonstrates:

• JWT authentication
• Spring Security filters
• REST API design
• JPA relationships
• Validation
• Exception handling
• Cloud deployment

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👨‍💻 Author

Aziz Backend Developer (Java + Spring Boot)

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⭐ If you like this project

Give it a ⭐ on GitHub!