Application.java

package com.gms;

import com.gms.service.AppService;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.server.ErrorPage;
import org.springframework.boot.web.server.ErrorPageRegistrar;
import org.springframework.boot.web.server.ErrorPageRegistry;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.context.annotation.Bean;
import org.springframework.http.HttpStatus;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;


/**
 * Entry point to the application.
 *
 * @author Asiel Leal Celdeiro | lealceldeiro@gmail.com
 * @version 0.1
 */
@SpringBootApplication
public class Application extends SpringBootServletInitializer {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    /** Extends SpringBootServletInitializer and overrides the configure method (See:
     * https://stackoverflow.com/questions/39567434/spring-boot-application-gives-404-when-deployed-to-tomcat-but-works-with-embedde)
     * and officially here: https://docs.spring.io/spring-boot/docs/1.5.6.RELEASE/reference/htmlsingle/#howto-create-a-deployable-war-file
     * @param builder SpringApplicationBuilder
     * @return SpringApplicationBuilder
     */
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
        return builder.sources(Application.class);
    }

    //region beans

    //start up runner
    @Bean
    public CommandLineRunner commandLineRunner(AppService appService) {
        return strings -> {
            if (!appService.isInitialLoadOK()) {
                System.exit(1);
            }
        };
    }

    //bCrypt
    @Bean
    public BCryptPasswordEncoder bCryptPasswordEncoder() {
        return new BCryptPasswordEncoder();
    }

    @Bean
    public ErrorPageRegistrar errorPageRegistrar() {
        return new IndexRedirectionPageRegistrar();
    }

    // used by bean
    private static class IndexRedirectionPageRegistrar implements ErrorPageRegistrar {
        @Override
        public void registerErrorPages(ErrorPageRegistry registry) {
            registry.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/index.html"));
        }
    }

    //endregion
}