Spring Boot development tools make the application development process simpler. Projects will include the developer tools if the following dependency is added to the Maven pom.xml file:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>            <scope>runtime</scope>
</dependency>

Development tools are disabled when you create a fully-packed production version of your application.

The application is automatically restarted when you make changes to your project's classpath files. You can test that by adding one comment line to your main class: 

package com.packt.cardatabase;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class CardatabaseApplication {

  public static void main(String[] args) {
    // After adding this comment the application is restarted
    SpringApplication.run(CardatabaseApplication.class, args);
  }
}

After saving the file, you can see in the console that the application has restarted.