How does a Spring Boot console based application work?

Question

If I am developing a rather simple Spring Boot console-based application, I am unsure about the placement of the main execution code. Should I place it in the public static void main(String[] args) method, or have the main application class implement the CommandLineRunner interface and place the code in the run(String... args) method?

I will use an example as the context. Say I have the following [rudimentary] application (coded to interfaces, Spring style):

Application.java

public class Application {    @Autowired   private GreeterService greeterService;    public static void main(String[] args) {     // ******     // *** Where do I place the following line of code     // *** in a Spring Boot version of this application?     // ******     System.out.println(greeterService.greet(args));   } } 

GreeterService.java (interface)

public interface GreeterService {   String greet(String[] tokens); } 

GreeterServiceImpl.java (implementation class)

@Service public class GreeterServiceImpl implements GreeterService {   public String greet(String[] tokens) {      String defaultMessage = "hello world";      if (args == null || args.length == 0) {       return defaultMessage;     }      StringBuilder message = new StringBuilder();     for (String token : tokens) {       if (token == null) continue;       message.append(token).append('-');     }      return message.length() > 0 ? message.toString() : defaultMessage;   } } 

The equivalent Spring Boot version of Application.java would be something along the lines: GreeterServiceImpl.java (implementation class)

@EnableAutoConfiguration public class Application     // *** Should I bother to implement this interface for this simple app?     implements CommandLineRunner {      @Autowired     private GreeterService greeterService;      public static void main(String[] args) {         SpringApplication.run(Application.class, args);         System.out.println(greeterService.greet(args)); // here?     }      // Only if I implement the CommandLineRunner interface...     public void run(String... args) throws Exception {         System.out.println(greeterService.greet(args)); // or here?     } } 

Answer 1

You should have a standard loader:

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

and implement a CommandLineRunner interface with @Component annotation

    @Component     public class MyRunner implements CommandLineRunner {         @Override            public void run(String... args) throws Exception {        }    } 

@EnableAutoConfiguration will do the usual SpringBoot magic.

UPDATE:

As @jeton suggests the latest Springboot implements a straight:

spring.main.web-application-type=none spring.main.banner-mode=off 

See docs at 72.2