A great API is one which people use. Not necessarily the one with the best design or technology behind it. If a developer from half a world away can successfully use your API without losing their minds, you've done a great job. Good documentation makes that possible and that's where OpenAPI and Swagger come in. Their auto-generated, interactive and standardized documentation takes your API from meh to something everyone wants to build around all with a few lines of setup. In this guide, I'll show you how to build a Java REST API using Spring Boot and integrate OpenAPI for simple and clear documentation. In five steps, you'll learn some key concepts, pro tips and how to make your API developer-friendly. 1. Setting up the Project Let's start by creating a new project using Spring Boot and Gradle (Groovy) in IntelliJ IDEA.…