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In this post, we will create a simple Spring Boot application which will run on embedded Apache Tomcat.

Let's start building Spring Boot Application.

Adding dependencies in pom.xml

We will first add spring-boot-starter-parent as parent of our maven based project.

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>1.5.1.RELEASE</version>
</parent>

The benefit of adding spring-boot-starter-parent is that version managing of dependency is easy. You can omit the required version on the dependency. It will pick the one configured the parent pom or from starters pom. Also, it conveniently setup the build related configurations as well.

Adding spring-boot-starter-web dependency

This will configure/ add all the required dependencies for spring-web module.

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Writing App class

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

@SpringBootApplication indicates that class is configuration class and also trigger the auto-configure through @EnableAutoConfiguration and component scanning through @ComponentScan annotation in it.

In the main() of App class, we have delegated the call to run() method of SpringApplication. SpringApplication will bootstrap and auto-configure our application and in our case will start the embedded tomcat server. In run method, we have passed App.class as argument which tells Spring that this is our primary spring component (helps in bootstrapping).

Writing HelloGbController

@RestController
public class HelloGbController {
  @GetMapping
  public String helloGb() {
    return "Gaurav Bytes says, \"Hello There!!!\"";
  }
}

I have used two annotations @RestController and @GetMapping. You can read more on new annotation introduced by Spring here.

@RestController signifies that this class is web @Controller and spring will consider it to handle incoming web requests.

Running the application

You can use maven command mvn spring-boot:run to run it as Spring Boot application and when you hit the localhost:8080 on your web browser, you will see the below web page.

Creating a jar for spring boot application

You need to add spring-boot-maven-plugin plugin to your build configuration in pom.xml and then you can create a jar with maven command mvn repackage and simply run it as jar with command java -jar spring-boot-quickstart-0.0.1-SNAPSHOT.jar.

<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
</plugin>

This is how you can build a simple spring boot application. I hope you find this post helpful. You can download the example code from Github.