Spring in Action

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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.

You’ll find several options for initializing a Spring application. Although I could walk you through the steps of manually creating a project directory structure and defining a build specification, that’s wasted time—time better spent writing application code. Therefore, you’re going to lean on the Spring Initializr to bootstrap your application.

about the technology

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. If you’re not a Spring Tool Suite user, that’s fine; we can still be friends. Hop over to the appendix and substitute the Initializr option that suits you best for the instructions in the following sections. But know that throughout this book, I may occasionally reference features specific to Spring Tool Suite, such as the Spring Boot Dashboard. If you’re not using Spring Tool Suite, you’ll need to adapt those instructions to fit your IDE. This book contains many examples of source code both in numbered listings and inline with normal text. In both cases, source code is formatted in a fixed-width font like this to separate it from ordinary text. Sometimes code is also in bold to highlight code that has changed from previous steps in the chapter, such as when a new feature adds to an existing line of code. Chapter 10 introduces Project Reactor, the reactive programming library that underpins Spring 5’s reactive features. 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).

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, in chapter 19 you’ll see how to deploy your Spring application in a variety of production environments. Chapter 14 shows how to centralize application configuration in a configuration server that shares configuration across multiple microservices.Next, take note of the element and, more specifically, its child. This specifies that your project has spring-boot-starter-parent as its parent POM. Among other things, this parent POM provides dependency management for several libraries commonly used in Spring projects. For those libraries covered by the parent POM, you won’t have to specify a version, as it’s inherited from the parent. The version, 2.0.4.RELEASE, indicates that you’re using Spring Boot 2.0.4 and, thus, will inherit dependency management as defined by that version of Spring Boot. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. 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’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.

Spring in Action, 5th edition is for Java developers who want to get started with Spring Boot and the Spring Framework as well as for seasoned Spring developers who want to go beyond the basics and learn the newest features of Spring. How this book is organized: a roadmap

Figure 1.1. Application components are managed and injected into each other by the Spring application context. 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 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.