As I previously mentioned, we will run most of the recipes using the Spring Boot Framework which eases the development of applications based on the Spring Framework. So to run this recipe, you just need an environment where you can download some files from the internet, Java 8 properly configured on your machine, and the CURL tool.

The following steps describe how to prepare the environment and show how to generate a simple project from the Spring Initializr website which will be executed using the appropriate Maven commands:

@SpringBootApplication 
public class SimplemvcApplication { 
   public static void main(String[] args) { 
         SpringApplication.run(SimplemvcApplication.class, args); 
   } 
} 

@Controller @SpringBootApplication 
public class SimplemvcApplication { 
   public static void main(String[] args) { 
         SpringApplication.run(SimplemvcApplication.class, args); 
   } 
} 

@GetMapping("/message") 
public ResponseEntity<String> getMessage() { 
   return ResponseEntity.ok("Hello!"); 
} 

Started SimplemvcApplication in 13.558 seconds (JVM running for 14.011)

curl "http://localhost:8080/message"

mvn spring-boot:run

MVN_HOME=/Users/{your_user_name}/maven-3.5.0 
export PATH=$PATH:$MVN_HOME/bin 

mvn --version.

Because of the usage of Spring Boot we can take advantage of projects like Spring MVC and Spring Security. These Spring projects help us to write web applications, REST APIs, and help us to secure our applications. By using the Spring Security OAuth2 project, for example, we can configure our own OAuth 2.0 Providers in addition, to act like clients. This is important because someone trying to write his own OAuth Provider will have to deal with too many details which could easily lead to an insecure OAuth Provider. Spring Security OAuth2 already addresses the main concerns any developer would have to think about.

In addition, Spring Boot eases the initial steps for the bootstrap of the application. When creating a Spring project without Spring Boot we need to deal with dependencies manually by taking care of possible library conflicts. To solve this problem, Spring Boot has some pre-configured modules provided by starters. As an example of a useful starter, let's consider an application with Spring Data JPA. Instead of declaring all the dependencies for hibernate, entity-manager, and transaction-api, just by declaring spring-boot-starter-data-jpa all the dependencies will be imported automatically.

While starting using Spring Boot, things can still become easier by using the Spring Initializr service provided by Pivotal (the Spring maintainer now).

All the examples presented in Java can be imported and executed on any Java IDE, but we will use Eclipse just because it is a large, accepted tool among developers around the world. Although this book presents recipes using Eclipse, you can also stick with your preferred tool if you want.

Nowadays, many projects have been designed using Gradle, but many developers are still used to creating their projects using Maven to manage dependencies and the project itself. So, to avoid trick bugs with IDE plugins or any other kind of issue, the recipes using Spring Boot will be managed by Maven. In addition, Eclipse IDE already comes with a Maven plugin which at the time of writing this book was not true for Gradle. To run projects with Gradle in Eclipse, you must install a specific plugin.

Spring Boot provides a lot of starters to help you develop applications using a plethora of tools and libraries. If you want to search for more just go to http://docs.spring.io/spring-boot/docs/1.5.7.RELEASE/reference/htmlsingle/#using-boot-starter.