It's important that you understand how we will be using examples in this book. Since the book tries to give lots of detail on Spring Security 5 and its reactive aspects, we will not have a single use case throughout the book. Instead, we will keep creating small projects to help you understand each of the core concepts covered. Here are some of the important aspects of the code base within this book:

• Most concepts will be covered using a standalone Spring Boot project.
• At times, we will use the famous Spring Initializr (https://start.spring.io/) to bootstrap our sample Spring Boot application. In other cases, we will start with a base project that we already have and introduce more concepts through code.
• Generally, we will be using Java configuration. At times, we might use XML-based configurations.
• We will keep our examples as simple as possible so that we don't lose focus on the core concept being introduced.
• Even though this book is focused on reactive applications, we will not be covering this each time it is introduced. At times, we will just be doing plain, old imperative programming as it is more important to know reactive programming and use it when required. It's not that we have to use reactive code everywhere possible, just use it where you see fit.
• We will be using VS Code for all the projects, and we'll be using the extensions available in VS Code to the fullest. We will also be using the Spring Initializr extension rather than using online Spring Initializr.
• We will be using Maven most of the time in this book. There might be a case where we try Gradle.
• Sometimes, we might use IntelliJ IDE and you'll see some screenshots showing this.
• We'll be using the latest Spring Boot release version, namely 2.0.0. RELEASE. This is the latest release version of Spring Boot at the time of writing this book.