Changing default welcome-page for spring-boot application deployed as a war

It's not too hard to do... you just need to forward the default mapping...

@Configuration
public class DefaultView extends WebMvcConfigurerAdapter{

    @Override
    public void addViewControllers( ViewControllerRegistry registry ) {
        registry.addViewController( "/" ).setViewName( "forward:/yourpage.html" );
        registry.setOrder( Ordered.HIGHEST_PRECEDENCE );
        super.addViewControllers( registry );
    }
}

Well, a few years passed since the last answer - and code evolves..

This won't work on Spring 5 / Java 8+, you should implement the interface and override the default method.

import org.springframework.core.Ordered;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class DefaultViewConfig implements WebMvcConfigurer {
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/").setViewName("/homepage.html");
        registry.setOrder(Ordered.HIGHEST_PRECEDENCE);
    }
}

Following Michael's tutorial, I was able to just map / to my index.gsp file.

@Controller
class Routes {

    @RequestMapping({
        "/",
        "/bikes",
        "/milages",
        "/gallery",
        "/tracks",
        "/tracks/{id:\\w+}",
        "/location",
        "/about"
    })
    public String index() {
        return "forward:/index.gsp";
    }
}