currencyExchanger

PREREQUISITE

Java 17 JDK installed, environment variables are set up: https://www.oracle.com/java/technologies/javase/jdk17-archive-downloads.html

(I suggest using SDKMAN no matter which OS You use: https://sdkman.io/)

Goal of the task

An APIs to calculate the exchange rates need to be exposed defined here under:

• GET /exchange?from=EUR&to=PLN&date=2020-12-05
  • from and to parameters should accept currency codes
  • date should accept ISO8601 date format (date only)
  • 2020-12-05, EUR and PLN are used as examples
  • Should return the exchange rate between the provided currencies
  • Should use the exchange rate of the day provided in the query parameter date, if not found return 404 not found
  • date is optional, if not present latest exchange rate information should be used
  • Result should be in JSON format as shown in Appendix 1
  • All the information should be retrieved from the cached data in the database
  • A counter in the database should be incremented for both currencies indicating a request was made for the date selected

To be able to retrieve the data, a scheduler also needs to be implemented that runs at 12:05 AM GMT and inserts the exchange rates into the database from http://data.fixer.io/api/latest

For this project use as base currency whatever https://fixer.io/ selects for your API key.

running with CLI [dev profile, H2 in memory database]

./mvnw spring-boot:run -Dspring-boot.run.profiles=dev

running tests with CLI

./mvnw test

Swagger UI access when application is running

Swagger UI

App properties

datasource, external API url, api-key and spreads are customizable by editing

• application-dev.yml file [DEV]
• application-prod.yml file [PROD]

Technologies

• Java
• Spring (Boot, AOP, Retry)
• maven
• Hibernate
• JPA
• Swagger
• Slf4J
• lombok
• jUnit5

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Ideas for future improvements

1. Adapt to reactive world with Spring Webflux
2. Add k8s, helm and terraform configuration
3. Write some performance and e2e tests

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Appendix 1

{
  “from” : “EUR”,
  “to” : “PLN”,
  “exchange”: 4.4405487565413254124
}