Quicken Backend Internship Project

A Spring Boot REST API for managing accounts and transactions with financial summary calculations.

Project Overview

This application provides APIs to:

• List all accounts
• Get financial summaries for accounts within date ranges
• View daily breakdowns of income and expenses

Project Structure

src/
├── main/
│   ├── java/com/nicolas/quicken/
│   │   ├── QuickenApplication.java       # Main application class
│   │   ├── model/
│   │   │   ├── Account.java              # Account entity
│   │   │   └── Transaction.java          # Transaction entity
│   │   ├── repository/
│   │   │   ├── AccountRepository.java    # JDBC queries for accounts
│   │   │   └── TransactionRepository.java # JDBC queries for transactions
│   │   ├── service/
│   │   │   └── AccountService.java       # Business logic & calculations
│   │   └── controller/
│   │       └── AccountController.java    # REST API endpoints
│   └── resources/
│       ├── application.properties        # Database configuration
│       └── quicken_project.sql           # Database schema & sample data
└── test/
    └── java/com/nicolas/quicken/
        └── service/
            └── AccountServiceTest.java   # Unit tests

Setup Instructions

Prerequisites

• Java 21 or higher
• Git

Clone the Repository

git clone git@github.com:NickB-30/quicken-backend.git
cd quicken-backend

Build the Project

./gradlew build

Running the Application

./gradlew bootRun

The application will start on http://localhost:8080

API Endpoints

1. Get All Accounts

Endpoint: GET /api/accounts

Description: Returns a list of all accounts

Example Request:

curl http://localhost:8080/api/accounts

Example Response:

[
  {
    "id": 1,
    "name": "Personal Finances 2024",
    "description": "Personal income and household expenses"
  },
  {
    "id": 2,
    "name": "Small Business 2024",
    "description": "Simple small business cashflow"
  }
]

2. Get Account Summary

Endpoint: GET /api/accounts/{accountId}/summary?from=YYYY-MM-DD&to=YYYY-MM-DD

Description: Returns total income, expenses, and net for an account within a date range

Parameters:

• accountId (path) - The account ID
• from (query) - Start date (YYYY-MM-DD)
• to (query) - End date (YYYY-MM-DD)

Example Request:

curl "http://localhost:8080/api/accounts/1/summary?from=2024-01-01&to=2024-12-31"

Example Response:

{
  "totalIncome": 7400.00,
  "totalExpenses": 3902.80,
  "net": 3497.20
}

3. Get Daily Summary (Bonus Feature)

Endpoint: GET /api/accounts/{accountId}/daily-summary?from=YYYY-MM-DD&to=YYYY-MM-DD

Description: Returns a daily breakdown of income, expenses, and net for each day in the date range

Parameters:

• accountId (path) - The account ID
• from (query) - Start date (YYYY-MM-DD)
• to (query) - End date (YYYY-MM-DD)

Example Request:

curl "http://localhost:8080/api/accounts/1/daily-summary?from=2024-01-01&to=2024-01-05"

Example Response:

[
  {
    "date": "2024-01-01",
    "income": 3500,
    "expenses": 0,
    "net": 3500
  },
  {
    "date": "2024-01-02",
    "income": 0,
    "expenses": 1500,
    "net": -1500
  },
  {
    "date": "2024-01-05",
    "income": 0,
    "expenses": 220.45,
    "net": -220.45
  }
]

Running Tests

Run all unit tests:

./gradlew test

Test Coverage:

• Account summary with mixed income and expenses
• Account summary with no transactions (edge case)
• Account summary with only income (edge case)
• Daily summary with transactions across multiple days
• Account summary for single day date range (boundary edge case)

All tests use Mockito to mock repository dependencies and focus on testing the business logic in the service layer.

Design Decisions

Why BigDecimal for Money?

BigDecimal is used for all financial amounts to ensure precise calculations without floating-point errors, which is critical for financial applications.

Architecture

The application follows a clean Controller → Service → Repository layered architecture:

• Controllers handle HTTP requests/responses
• Services contain business logic and calculations
• Repositories execute SQL queries using JdbcTemplate

Lombok for Code Simplification

Lombok annotations (@Data, @AllArgsConstructor, @NoArgsConstructor) are used throughout the project to automatically generate getters, setters, constructors, and other boilerplate code. This keeps the codebase clean and maintainable while reducing repetitive code.

Author

Nicolas Beringer
Backend Internship Project - Quicken

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This project was created as part of the Quicken Backend Internship application process.