As the Taco Cloud application grows, you’ll fill in this barebones project structure with Java code, images, stylesheets, tests, and other collateral that will make your project more complete. But in the meantime, let’s dig a little deeper into a few of the items that Spring Initializr provided. TacoCloudApplicationTests.java—This is a simple test class that ensures that the Spring application context loads successfully. You’ll add more tests to the mix as you develop the application. The act of wiring beans together is based on a pattern known as dependency injection (DI). Rather than have components create and maintain the lifecycle of other beans that they depend on, a dependency-injected application relies on a separate entity (the container) to create and maintain all components and inject those into the beans that need them. This is done typically through constructor arguments or property accessor methods.

Although the Greek philosopher Heraclitus wasn’t well known as a software developer, he seemed to have a good handle on the subject. He has been quoted as saying, The only constant is change. That statement captures a foundational truth of software development.The way we develop applications today is different than it was a year ago, 5 years ago, 10 years ago, and certainly 15 years ago, when an initial form of the Spring Framework was introduced in Rod Johnson’s book, Expert One-on-One J2EE Design and Development (Wrox, 2002, http://mng.bz/oVjy). When you filled out the Initializr form, you specified that your project should be built with Maven. Therefore, the Spring Initializr gave you a pom.xml file already populated with the choices you made. The following listing shows the entire pom.xml file provided by the Initializr. 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.

Historically, the way you would guide Spring’s application context to wire beans together was with one or more XML files that described the components and their relationship to other components. For example, the following XML declares two beans, an InventoryService bean and a ProductService bean, and wires the InventoryService bean into ProductService via a constructor argument:

Chapter 16 introduces the Spring Boot Actuator, an extension to Spring Boot that exposes the internals of a running Spring application as REST endpoints. Finally, the build specification ends with the Spring Boot plugin. This plugin performs a few important functions: Finally, in chapter 19 you’ll see how to deploy your Spring application in a variety of production environments. Craig Walls is an engineer at VMware, a member of the Spring engineering team, a popular author, and a frequent conference speaker. Chapter 14 shows how to centralize application configuration in a configuration server that shares configuration across multiple microservices.

As for the dependencies themselves, you can either expand the various sections and seek out the desired dependencies manually, or search for them in the search box at the top of the Available list. For the Taco Cloud application, you’ll start with the dependencies shown in figure 1.4. CRAIG WALLS is a principal engineer with Pivotal. He’s a zealous promoter of the Spring Framework, speaking frequently at local user groups and conferences and writing about Spring. When he’s not slinging code, Craig is planning his next trip to Disney World or Disneyland and spending as much time as he can with his wife, two daughters, two birds, and three dogs. About the cover illustration But enough of this chitchat, yakety-yak, and flimflam. This book’s title includes the phrase in action, so let’s get moving, and you can start writing your first application with Spring. 1.2. Initializing a Spring application 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. I’m happy to say that this fifth edition of Spring in Action covers all of this and more! If you’re a seasoned veteran with Spring, Spring in Action, Fifth Edition will be your guide to everything new that Spring has to offer. On the other hand, if you’re new to Spring, then there’s no better time than now to get in on the action and the first few chapters will get you up and running in no time!application.properties—This file is initially empty, but offers a place where you can specify configuration properties. We’ll tinker with this file a little in this chapter, but I’ll postpone a detailed explanation of configuration properties to chapter 5. Spring in Action, 5th Edition is the fully updated revision of Manning's bestselling Spring in Action. This new edition includes all Spring 5.0 updates, along with new examples on reactive programming, Spring WebFlux, and microservices. You'll also find the latest Spring best practices, including Spring Boot for application setup and configuration. One of the most amazing things that Spring and Spring Boot do is to automatically provide all of the foundational plumbing for an application, leaving you as a developer to focus primarily on the logic that’s unique to your application. Unfortunately, no such magic exists for writing a book. Or does it?

Every single release of Spring, Spring Boot, and all of the other projects in the Spring ecosystem unleashes some new amazing capabilities that rekindle the fun in developing applications. With Spring reaching a significant milestone with its 5.0 release and Spring Boot releasing version 2.0, there’s so much more Spring to enjoy that it was a no-brainer to write another edition of Spring in Action. Chapter 11 revisits REST API development, introducing Spring WebFlex, a new web framework that borrows much from Spring MVC while offering a new reactive model for web development. Part 1 of this book will get you started writing a Spring application, learning the foundations of Spring along the way. The only book you’ll ever need to learn and master the Spring ecosystem. This update is a must-read.Chapter 5 reveals how to configure a Spring application using Spring Boot configuration properties. You’ll also learn how to selectively apply configuration using profiles. Finally, to my beautiful wife Raymie, the love of my life, my sweetest dream, and my inspiration: Thank you for your encouragement and for putting up with another book project. And to my sweet and wonderful girls, Maisy and Madi: I am so proud of you and of the amazing young ladies you are becoming. I love all of you more than you can imagine or I can possible express. About this book