WeatherApp

Overview

WeatherApp is a Spring Boot application that fetches, processes, and analyzes weather data asynchronously. It retrieves weather forecasts from an external API (OpenWeatherMap) and provides a summary, including the average temperature, hottest day, and coldest day for the past 7 days.

Features

• Fetches weather data using WebClient.
• Processes and analyzes weather data.
• Computes the average temperature, hottest day, and coldest day.
• Caches results for 30 minutes using Caffeine Cache.
• Handles API failures and invalid city names gracefully.
• Implements asynchronous execution with @Async and CompletableFuture.
• Includes unit tests for service and controller layers using JUnit and Mockito.

Technologies Used

• Java 17
• Spring Boot 3+
• Spring Web
• Spring Cache (Caffeine)
• Spring WebFlux (for WebClient)
• Spring Boot Starter Test
• Lombok (for reducing boilerplate code)
• Mockito & JUnit (for unit testing)

Architecture Overview

The application follows a layered architecture:

• Controller Layer: Handles incoming HTTP requests.
• Service Layer: Fetches, processes, and caches weather data.
• Exception Handling: Provides robust error handling for API failures and invalid inputs.
• Caching Layer: Uses Caffeine Cache to store results for 30 minutes.
• Asynchronous Execution: Uses @Async and CompletableFuture to perform non-blocking API calls.

Requirements

Input

A city name provided as a query parameter to the endpoint:

GET /weather?city=London

Output

A JSON response summarizing the weather for the given city:

{
  "city": "London",
  "averageTemperature": 15.5,
  "hottestDay": "2024-11-20",
  "coldestDay": "2024-11-18"
}

Technologies Used

• Java 17
• Spring Boot 3+
• Spring Web
• Spring Cache (Caffeine)
• Spring WebFlux (for WebClient)
• Spring Boot Starter Test
• Lombok (for reducing boilerplate code)
• Mockito & JUnit (for unit testing)

Setup & Installation

Prerequisites

Ensure you have the following installed:

• Java 17+
• Maven 3+
• An OpenWeatherMap API key

Steps to Run

1. Clone the repository:

git clone https://github.com/NelushGayashan/WeatherApp.git
cd WeatherApp

2. Configure the OpenWeatherMap API key: To use the weather API, you need to set your OpenWeatherMap API key as an environment variable.

Steps:

1. Obtain your API key from OpenWeatherMap.

2. Set the API key as an environment variable on your system:

   • On Linux/macOS:

     export WEATHER_API_KEY=your_openweathermap_api_key

   • On Windows (Command Prompt):

     set WEATHER_API_KEY=your_openweathermap_api_key

   • On Windows (PowerShell):

     $env:WEATHER_API_KEY="your_openweathermap_api_key"

3. The application will automatically use this environment variable to access the API key. Make sure to replace your_openweathermap_api_key with the actual key you received.

4. Build and run the application:

mvn clean install
mvn spring-boot:run

4. Access the API:

http://localhost:8080/weather?city=London

Caching Strategy

• Uses Spring Cache with Caffeine.
• Cache timeout: 30 minutes.
• Cache key: City name.

Error Handling

Error Type	HTTP Status	Description
Invalid City Name	404	The specified city was not found.
API Key Invalid/Missing	401	The provided API key is incorrect.
External API Failure	503	OpenWeatherMap API is unavailable.
Generic Error	500	An unexpected error occurred.

Running Tests

Run unit tests using:

mvn test

Sample API Calls & Responses

Successful Response

Request:

GET /weather?city=London

Response

Successful Response

Response:

{
  "city": "London",
  "averageTemperature": 15.5,
  "hottestDay": "2024-11-20",
  "coldestDay": "2024-11-18"
}

Error Response (Invalid City)

Request:

GET /weather?city=InvalidCity

Response:

{
  "error": "City not found: InvalidCity"
}

License

This project is licensed under the MIT License.