Convert Spring application to SpringBoot

I'm building a toy application based on the following tutorial:
https://www.baeldung.com/spring-security-login

I've got a working web app, and would like to convert it to SpringBoot.

I wonder how that could be done?

The current application initialiser looks like that:

public class AppInitializer implements WebApplicationInitializer {

  @Override
  public void onStartup(final ServletContext sc) throws ServletException {

    AnnotationConfigWebApplicationContext root = new AnnotationConfigWebApplicationContext();

    root.scan("com.baeldung");
    sc.addListener(new ContextLoaderListener(root));

    ServletRegistration.Dynamic appServlet = sc.addServlet("mvc", new DispatcherServlet(new GenericWebApplicationContext()));
    appServlet.setLoadOnStartup(1);
    appServlet.addMapping("/");

    sc.addFilter("securityFilter", new DelegatingFilterProxy("springSecurityFilterChain"))
    .addMappingForUrlPatterns(null, false, "/*");

   }

}

Any tips for (preferably quick and easy) migration to SpringBoot are appreciated.

It's a gradle application (I migrated it from maven).

Springboot initialization and entry point is the main class annotated with @SpringBootApplication. For example, see below DemoApplication class.

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

You will need to look at the spring-boot-starter plugins as well.

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.3.4.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

You can generate a project using Springboot initializer and start moving your code.

Well, my question was caused by a confusion as to how the web context gets started and knows which controllers to use, so I was a bit stuck trying to wire up the WebApplicationInitializer and AnnotationConfigWebApplicationContext but then...

since it's a web-based application that uses controllers, all I had to do was to replace the main class with the following:

@SpringBootApplication
public class AppInitializer {

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

Then, since I've had controllers, as in:

@Controller
public class SecuredResourceController {

       @RequestMapping("/secured")
        public void secureResource(HttpServletRequest request, HttpServletResponse response) {
            System.out.println("accessing secured resource");
        }
    }

, the app would build and start the controller inside an embedded tomcat container, provided I've had the following dependencies:

implementation 'org.springframework.boot:spring-boot-starter'
implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'
implementation 'org.springframework.boot:spring-boot-starter-web'

Then, I just run

./gradlew bootRun

and the container gets started and processes the requests. Mystery's solved...