Figure 1.1. Application components are managed and injected into each other by the Spring application context. To get started with a new Spring project in Spring Tool Suite, go to the File menu and select New, and then Spring Starter Project. Figure 1.2 shows the menu structure to look for. Part 1 of this book will get you started writing a Spring application, learning the foundations of Spring along the way. Spring Boot enhances Spring development so much that it’s hard to imagine developing Spring applications without it. For that reason, this book treats Spring and Spring Boot as if they were one and the same. We’ll use Spring Boot as much as possible, and explicit configuration only when necessary. And, because Spring XML configuration is the old-school way of working with Spring, we’ll focus primarily on Spring’s Java-based configuration. Automatic configuration has its roots in the Spring techniques known as autowiring and component scanning. With component scanning, Spring can automatically discover components from an application’s classpath and create them as beans in the Spring application context. With autowiring, Spring automatically injects the components with the other beans that they depend on.

You may also notice that all three dependencies have the word starter in their artifact ID. Spring Boot starter dependencies are special in that they typically don’t have any library code themselves, but instead transitively pull in other libraries. These starter dependencies offer three primary benefits: Chapter 1 introduces Spring and Spring Boot and how to initialize a Spring project. In this chapter, you’ll take the first steps toward building a Spring application that you’ll expand upon throughout the course of the book. Spring Framework makes life easier for Java developers. New features in Spring 5 bring its productivity-focused approach to microservices, reactive development, and other modern application designs. With Spring Boot now fully integrated, you can start even complex projects with minimal configuration code. And the upgraded WebFlux framework supports reactive apps right out of the box!Chapter 12 takes a look at writing reactive data persistence with Spring Data to read and write data to Cassandra and Mongo databases.

Chapter 14 shows how to centralize application configuration in a configuration server that shares configuration across multiple microservices.Chapter 6 expands on the discussion of Spring MVC started in chapter 2 by looking at how to write REST APIs in Spring. In addition to the new reactive programming features of Spring 5, Spring Boot 2 now provides even more autoconfiguration support than ever before as well as a completely reimagined Actuator for peeking into and manipulating a running application.

You’re able to think of your dependencies in terms of what capabilities they provide, rather than in terms of library names. If you’re developing a web application, you’ll add the web starter dependency rather than a laundry list of individual libraries that enable you to write a web application.

Designed in 2003 as a lighter approach to J2EE development, Spring Framework has since become a standard choice for building enterprise applications and required knowledge for Java developers. Spring 4 provides full Java 8 integration along with key upgrades like new annotations for the IoC container, improvements to Spring Expression Language, and much-needed support for REST. Whether you're just discovering Spring or you want to absorb the new features, there's no better way to master Spring than with this book.