Expense Tracker API

Spring Boot backend for personal budgeting and expense tracking with JWT authentication, category management, transaction CRUD, and monthly analytics.

Features

• JWT-based auth with register/login and stateless request filtering
• User-scoped categories (income/expense) and validated transaction CRUD
• Monthly analytics (income, expense, net, category breakdown)
• PostgreSQL persistence via Spring Data JPA/Hibernate
• Maven build with Java 17 and Spring Boot 3.5

Tech Stack

• Java 17, Spring Boot 3.5 (Web, Data JPA, Security, Validation)
• PostgreSQL, Hibernate
• JSON Web Tokens (jjwt)
• Maven (wrapper included)

Prerequisites

• JDK 17+
• PostgreSQL running locally
• Maven (or use the provided ./mvnw wrapper)

Configuration

The app reads settings from application.properties (override with environment variables if preferred). Minimum settings to provide:

spring.datasource.url=jdbc:postgresql://localhost:5432/expensetracker
spring.datasource.username=fintrack
spring.datasource.password=javaproject1

jwt.secret=change-me-to-a-long-random-string
jwt.expirationMs=86400000   # 24h

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true    # optional

Environment variable equivalents: SPRING_DATASOURCE_URL, SPRING_DATASOURCE_USERNAME, SPRING_DATASOURCE_PASSWORD, JWT_SECRET, JWT_EXPIRATIONMS.

Run Locally

# install deps and start the API on http://localhost:8080
./mvnw spring-boot:run

# or build a runnable jar
./mvnw clean package
java -jar target/expensetracker-0.0.1-SNAPSHOT.jar

Quick API Guide

All /api/** routes require Authorization: Bearer <token> from /auth/login.

Auth

• POST /auth/register – { "email": "...", "password": "..." }
• POST /auth/login – returns { "message": "...", "token": "<jwt>" }

Categories

• POST /api/categories – create { "name": "Food", "type": "EXPENSE" }
• GET /api/categories – list categories for the authenticated user

Transactions

• GET /api/transactions – list transactions (sorted by date desc)
• POST /api/transactions – create { "amount": 25.50, "date": "2024-12-12", "description": "Lunch", "categoryId": "<uuid>" }
• GET /api/transactions/{id} – fetch a single transaction
• PUT /api/transactions/{id} – partial update (any of amount/date/description/categoryId)
• DELETE /api/transactions/{id} – remove a transaction

Analytics

• GET /api/analytics/monthly?year=2024&month=12 – totals plus per-category breakdown for the month

Sample Flow (cURL)

# register
curl -X POST http://localhost:8080/auth/register \
  -H "Content-Type: application/json" \
  -d '{"email":"you@example.com","password":"StrongPass1!"}'

# login
TOKEN=$(curl -s -X POST http://localhost:8080/auth/login \
  -H "Content-Type: application/json" \
  -d '{"email":"you@example.com","password":"StrongPass1!"}' | jq -r '.token')

# create a category
curl -X POST http://localhost:8080/api/categories \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name":"Groceries","type":"EXPENSE"}'

# create a transaction
curl -X POST http://localhost:8080/api/transactions \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"amount":42.15,"date":"2024-12-10","description":"Market","categoryId":"<category-uuid>"}'

Project Layout

• src/main/java/com/expensetracker/expensetracker/auth – JWT auth, filter, controller
• src/main/java/com/expensetracker/expensetracker/category – category domain + REST
• src/main/java/com/expensetracker/expensetracker/transaction – transaction domain + REST
• src/main/java/com/expensetracker/expensetracker/analytics – monthly analytics calculations
• src/main/resources/application.properties – default configuration

Testing

./mvnw test

Notes

• Requests are stateless; sessions are disabled.
• Data is user-scoped in services/repositories; include the bearer token for every protected request.
• Hibernate auto DDL is set to update for local dev; adjust before production.