How to Get Currency Conversion Rates with CurrencyLayer API in Java

Prerequisites and Dependencies

• Add the necessary dependencies to your project to work with JSON responses and HTTP requests. For instance, utilize libraries like Apache HttpClient and JSON-simple or Gson for parsing JSON data.

 

• Ensure you're using Java 8 or later for optimal compatibility and feature support.

Formulate HTTP Request

• Utilize the `HttpClient` class from Apache HTTP or Java's built-in `HttpURLConnection` to send a GET request to the CurrencyLayer API endpoint. The basic endpoint format for live data is `http://api.currencylayer.com/live?access_key=YOUR_ACCESS_KEY`.

 

• Construct the URL dynamically by appending desired parameters such as `currencies=` for specifying target currencies or `source` for setting the base currency.

Implementing the Request in Java

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class CurrencyLayerAPI {
    private static final String ACCESS_KEY = "YOUR_ACCESS_KEY";
    private static final String ENDPOINT = "http://api.currencylayer.com/live";

    public static String getCurrencyRates(String currencies) {
        String response = "";
        try {
            URL url = new URL(ENDPOINT + "?access_key=" + ACCESS_KEY + "&currencies=" + currencies);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");

            BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String inputLine;
            StringBuilder content = new StringBuilder();
            while ((inputLine = in.readLine()) != null) {
                content.append(inputLine);
            }

            in.close();
            conn.disconnect();
            response = content.toString();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return response;
    }
}

Parse JSON Response

• Use a JSON parsing library like JSON-simple, Gson, or Jackson to interpret the JSON response received from the API call.

 

• Extract specific data such as the exchange rates for the target currencies by navigating through the JSON hierarchy.

Implementing JSON Parsing

import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

public class CurrencyParser {

    public static void main(String[] args) {
        String jsonResponse = CurrencyLayerAPI.getCurrencyRates("EUR,GBP,JPY");
        JsonObject jsonObject = JsonParser.parseString(jsonResponse).getAsJsonObject();
        JsonObject quotes = jsonObject.getAsJsonObject("quotes");

        double usdToEur = quotes.get("USDEUR").getAsDouble();
        double usdToGbp = quotes.get("USDGBP").getAsDouble();
        double usdToJpy = quotes.get("USDJPY").getAsDouble();

        System.out.println("USD to EUR: " + usdToEur);
        System.out.println("USD to GBP: " + usdToGbp);
        System.out.println("USD to JPY: " + usdToJpy);
    }
}

Handle Possible Errors and Edge Cases

• Ensure robust error handling is in place in case of network issues or invalid API responses. Implement try-catch blocks and validate responses before parsing.

 

• Consider edge cases like invalid currency codes or an exceeded API request limit, and provide meaningful error messages or fallback mechanisms.

Test and Integrate

• Test your integration thoroughly to ensure that it processes various responses correctly, from successful requests to error scenarios.

 

• Integrate the currency conversion feature into your broader Java application, ensuring smooth interaction with other components and data sources.

Optimize for Performance

• Consider caching frequent API responses locally to minimize API calls and reduce latency, especially for applications requiring frequent currency rate lookups.

 

• Use thread pools or asynchronous programming techniques if the currency conversions occur frequently or in a performance-critical section of your application.