Nothing beats a good, modern, and recent introductory book on Spring. That's something I wish it was available some years back when I first encountered Spring.
Spring is a massive ecosystem. In this focused, hands-on guide you'll learn the parts you really need and learn them really well.
Spring is a must-learn tool for Java developers. Spring Quickly
introduces you to Java development with Spring by concentrating on the core concepts you'll use in every application you build. You'll learn how to refactor an existing application to Spring, how to use Spring tools to make SQL database requests and REST calls, and how to secure your projects with Spring Security. There's always more to learn, and this book will make your next steps much easier.