Crypto Price Checker

Ever wondered what the price of Bitcoin and Ethereum is on the move? Look no further, a fast Crypto Price Checker built using Spring Boot for the backend and React Native (expo) for the frontend. Fetches real time cryptocurrency prices using CoinGecko API and displays them in an intuitive mobile app.

Features

• Get real time Crypto prices for popular currencies (Bitcoin, Ethereum, etc)
• Fetches price based on currency selected (GBP/USD)
• Backend uses Springboot
• Frontend built with React Native (Expo Client)
• Appearance based on System Settings (Light/Dark mode)

Tech Stack

Backend:

• Java/SpringBoot (REST API)
• Uses CoinGecko API
• Mockito + Junit for testing

Frontend:

• React Native and Expo Client

How it works

• User selects a Crypto coin (e.g. Bitcoin) and selects currency (e.g. GBP) in the React Native app (runs on my physical Iphone)
• Frontend sends a request to Springboot backend with the selected coin and currency as query parameters

const url = http://ipaddress:8080/api/CryptoPrice?cryptoId=${selectedCrypto}&currency=${selectedCurrency};

local host 8080 - network address that points to my own computer

Uses my computers IP address to connect to the local server

• Springboot dynamically builds API URL with @RequestParam cryptoId/currency
• Springboot makes a request to Coingecko API get crypto price by id and retrieves JSON response
• JSON response is stored as POJO (CryptoData)
• Controller sends back price to React Native frontend as response and frontend displays crypto price
• There are also validation/error messages (e.g. if 500 error occurs, if coin is not selected, etc.).

Testing

The frontend was tested manually using Expo on my Iphone

Backend:

• TestingCryptoController:
  • Mocks API response to ensure price is being retrieve and request handling
  • Handles errors when fetching data such as 500 errors
• TestingCryptoService:
  • Mocks API response and JSON values are extracted correctly

Mockito to mock dependencies instead mocking the class under test

Getting Started

Prequisites:

• Java 17+
• NodeJS 18+
• Clone the repository

Backend:

• Set up application.properties with API URL - You can use CoinGecko's free API

Ensure - ids={cryptoId}&vs_currencies={currency}

• Run the backend and test on port 8080

http://localhost:8080/api/CryptoPrice?cryptoId=ethereum&currency=usd

Frontend:

• Install npm and nodeJS
• Ensure you have the dependencies installed (node modules)
• run "npx expo start" and scan QR code

const url = http://ipaddress:8080/api/CryptoPrice?cryptoId=${selectedCrypto}&currency=${selectedCurrency};

Replace "ipaddress" with your own

https://reactnative.dev/docs/environment-setup to get started with React Native

App Examples

Further Work

• Improve frontend UI
• More crypto data such as market cap, price charts, etc.
• Auto refresh price

Notes

• CoinGecko Public API documentation - https://docs.coingecko.com/v3.0.1/reference/introduction
• Coin Price by IDs - https://docs.coingecko.com/v3.0.1/reference/simple-price
• Getting Started with React Native - https://reactnative.dev/docs/environment-setup