This is a very simple module that demonstrates implementation of a custom RESTful API in Drupal 8. Creating your own API with Drupal 8 has become a routine task that doesn't require a lot of work. However there are a lot of things I am not covering in this blog post, such as user login and user registration etc...

You could also look into Rest module (in core) to see how to use it's plugin API to extend core rest functionality.

I use Postman to test my API endpoints (this is an app that allows you to send POST/GET/PUT/DELETE etc.. requests and see reponses).

Test API module (test_api.module) contains the following files: