Microservices: Invoking Currency Exchange Microservice

Introduction

This tutorial demonstrates how to invoke a currency exchange microservice in a microservices architecture. Currency exchange services play a crucial role in distributed systems, allowing applications to fetch real-time exchange rates and perform currency conversions.

Invoking Currency Exchange Microservice

Prerequisites

Before starting, ensure that you have:

• A Java development environment
• A running instance of the Currency Exchange microservice
• An understanding of microservices architecture concepts

Steps

1. Create a New Spring Boot Project

Use Spring Initializr or your preferred method to create a new Spring Boot project for the application that will invoke the currency exchange microservice.

2. Implement a CurrencyConversionRequest Class

Create a class (CurrencyConversionRequest) to represent the data structure for currency conversion requests.

public class CurrencyConversionRequest {

    private String fromCurrency;
    private String toCurrency;
    private double amount;

    // Constructors, getters, and setters
}

3. Implement a CurrencyExchangeService

Create a service class (CurrencyExchangeService) to handle communication with the currency exchange microservice.

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

@Service
public class CurrencyExchangeService {

    @Autowired
    private RestTemplate restTemplate;

    public double convertCurrency(String from, String to, double amount) {
        // Invoke the Currency Exchange microservice
        String exchangeServiceUrl = "http://currency-exchange-service/currency-exchange/convert";
        CurrencyConversionRequest request = new CurrencyConversionRequest(from, to, amount);

        // Make a REST call to the currency exchange microservice
        double convertedAmount = restTemplate.postForObject(exchangeServiceUrl, request, Double.class);

        return convertedAmount;
    }
}

4. Configure Application Properties

Configure the application properties to set up the REST template and other properties.

# RestTemplate Configuration
spring.application.name=currency-conversion-service
currency-exchange-service-url=http://currency-exchange-service

5. Implement a CurrencyConversionController

Create a controller class (CurrencyConversionController) to expose a REST endpoint for currency conversion.

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/currency-conversion")
public class CurrencyConversionController {

    @Autowired
    private CurrencyExchangeService currencyExchangeService;

    @GetMapping("/convert")
    public double convertCurrency(@RequestParam String from, @RequestParam String to, @RequestParam double amount) {
        // Invoke the Currency Exchange microservice
        return currencyExchangeService.convertCurrency(from, to, amount);
    }
}

Explanation

• CurrencyConversionRequest Class: Represents the structure of a currency conversion request.
• CurrencyExchangeService: Communicates with the currency exchange microservice using a REST template.
• CurrencyConversionController: Exposes a REST endpoint for currency conversion.

Use

• Microservices Communication: Invoke the currency exchange microservice to get real-time exchange rates.
• Distributed Architecture: Integrate this microservice with other microservices for comprehensive functionality.
• Error Handling: Implement error handling for communication failures or unexpected responses.

Important Points

1. Service Discovery: Use service discovery mechanisms to locate the currency exchange microservice dynamically.
2. Load Balancing: Implement load balancing strategies for better resilience.
3. Circuit Breaker Pattern: Consider implementing the Circuit Breaker pattern for fault tolerance.

Summary

Invoking a currency exchange microservice is an essential aspect of microservices communication in a distributed system. By leveraging RESTful communication and appropriate service discovery mechanisms, microservices can seamlessly exchange information, enabling features like real-time currency conversion in applications.