# First Spring Boot application

In this chapter you will learn how to bootstrap a Spring Boot application using SpringInitializr. You will learn how to create a REST endpoint.

# Initialize the project

Navigate to https://start.spring.io (opens new window)
Create a new project with Gradle and Java 8. Select Spring Boot version 2.2.0 M3. Name the artifacts and group according the the following image. Add Spring Web as a dependency.
Click on Generate Project (or hit Alt+Enter) to download the generated project skeleton.
Extract the downloaded archive and import the Gradle project in the IDE of your choice. In IntelliJ create a new project from existing sources. Make sure to tick the Enable auto-import checkbox in the last step of the dialog.

Start the SpotifyPlaylistApplication. In the logs you should be able to see, that the Tomcat server has been started on port 8080:

2019-05-20 15:31:02.200  INFO 17572 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''

# Implement your first REST endpoint

Create the file HelloWorldController.java
Insert the following content. The @RestController tells Spring Boot that this is a REST endpoint. The @GetMapping defines an endpoint, which can be accessed with the HTTP GET method. For the other HTTP methods like POST, PUT, DELETE, ... the corresponding annotations also exist.
```
@RestController
public class HelloWorldController {

    @GetMapping("/hello")
    public String helloWorld() {
        return "Hello World!";
    }

}
```
Restart your Spring Boot application.
Visit http://localhost:8080/hello (opens new window) in your browser. You should be able to see the Hello World! message from your server.

# Add Swagger

Swagger (opens new window) is a tool for documenting and testing REST endpoints. The integration with Spring Boot is very easy.

Add Swagger in the dependencies section of your build.gradle file:

dependencies {
    // ...
    implementation 'io.springfox:springfox-swagger2:2.9.2'
    implementation 'io.springfox:springfox-swagger-ui:2.9.2'
    implementation 'org.springframework.plugin:spring-plugin-core:1.2.0.RELEASE'
}

Create the file SwaggerConfig.java along the SpotifyPlaylistApplication.java file. Insert the following content:

@Configuration
@EnableSwagger2
public class SwaggerConfig {
    @Bean
    public Docket api() {
        return new Docket(DocumentationType.SWAGGER_2)
                .select()
                .apis(RequestHandlerSelectors.any())
                .paths(PathSelectors.any())
                .build();
    }
}

Restart your Spring Boot application and navigate to http://localhost:8080/swagger-ui.html (opens new window).
Open the hello-world-controller and click on the Get request. Click then on Try it out and execute the request from the Swagger UI.

# Tracking the application in Git

Before you can deploy your app to Heroku, you need to initialize a local Git repository and commit your application code to it.

git init
git add .
git commit -m "My first commit"

# Deploy the application to Heroku

Login using your Heroku credentials.
```
heroku login -i
```
The heroku create CLI command creates a new empty application on Heroku, along with an associated empty Git repository. The Git repository is automatically set as a remote for your local repository.
```
heroku apps:create <APPLICATION NAME> --region eu
```

Deploying the application

git push heroku master
...
https://<APPLICATION NAME>.herokuapp.com/ deployed to Heroku

EXERCISE

Test the deployed application using the Swagger UI.

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