Kotlin Starter

The Kotlin Starter is a very barebones project for getting started building a Kotlin backend with Spring Boot, leveraging some of the best practices I have come across while working with Kotlin over the past two years.

This project contains a very simple GET endpoint "/greet" which takes a single "name" parameter and returns a greeting with this name.

The greetings are loaded from the database via a Repository and the "business logic" can be found in a Service, following along from the well known MVCS paradigm.

Although this is completely overkill for simply saying hello to whoever is passed in, the point was to demonstrate how to test the different layers of the application.

Aim

To provide you with a very simple and pre-configured Spring Boot project that you can clone and immediately get going with, without having to waste time configuring everything.

Features

• Environment based configuration
• Linting (Ktlint - fix all issues with $ ktlint -F), Code coverage metrics
• Example CI setup with CircleCI
• Example tests
• Pre-configured embedded Postgres database for tests (no it does not slow down your tests)
• Configurable log levels
• Integration with micrometer for Statsd integration (easily replaceable with Prometheus)
• Dependency reports (lists outdated dependencies via $ ./gradlew dependencyUpdates i.e. example
• SwaggerUI integration: Run the application and point your browser at http://localhost:8080/swagger-ui.html

Getting started

Prerequisites

• ≥ Java 11: I'd recommend Jabba for managing your Java installations.
• Running postgres database. By default, the application looks for a database named kotlin-starter running on localhost:5432 with username postgres and password password. If your configuration does not match, please update the application.yml.

Running the app

Clone the repository: $ git clone git@github.com:maxkramer/kotlin-starter.git

Change directory into the kotlin-starter and run the application.

$ cd kotlin-starter
$ ./gradlew bootRun

To run the tests:

$ ./gradlew test

Configuring CORS

In the class CorsConfig you can enable CORS for individual endpoints, their HTTP methods, and which domains are allowed to access these endpoints. The property cors.allowed-origins in the application.yml is used to make the domain configurable for different environments, e.g. https://your-frontend.staging.project.org for staging and https://your-frontend.project.org for the production environment. In the provided configuration example the /greet endpoint is only allowed to be accessed by the configured domain.

FAQ (WIP)

• Why two environments?
• How to configure statsd?
• CI?