SpringApplication.run main method

Question

I created a project in Eclipse using the Spring Starter project template.

It automatically created an Application class file, and that path matches the path in the P

Answer 1

You need to run Application.run() because this method starts whole Spring Framework. Code below integrates your main() with Spring Boot.

Application.java

@SpringBootApplication
public class Application {

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

ReconTool.java

@Component
public class ReconTool implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {
        main(args);
    }

    public static void main(String[] args) {
        // Recon Logic
    }
}

Why not SpringApplication.run(ReconTool.class, args)

Because this way spring is not fully configured (no component scan etc.). Only bean defined in run() is created (ReconTool).

Example project: https://github.com/mariuszs/spring-run-magic

Answer 2

Using:

@ComponentScan
@EnableAutoConfiguration
public class Application {

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

        //do your ReconTool stuff
    }
}

will work in all circumstances. Whether you want to launch the application from the IDE, or the build tool.

Using maven just use mvn spring-boot:run

while in gradle it would be gradle bootRun

An alternative to adding code under the run method, is to have a Spring Bean that implements CommandLineRunner. That would look like:

@Component
public class ReconTool implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {
       //implement your business logic here
    }
}

Check out this guide from Spring's official guide repository.

The full Spring Boot documentation can be found here

Answer 3

One more way is to extend the application (as my application was to inherit and customize the parent). It invokes the parent and its commandlinerunner automatically.

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