spingboot 打成war访问项目出现404

@SpringBootApplication

public class Demo3Applicationextends SpringBootServletInitializer {

@Override

    protected SpringApplicationBuilderconfigure(SpringApplicationBuilder application) {

return application.sources(Demo3Application.class);

    }

public static void main(String[] args) {

SpringApplication.run(Demo3Application.class, args);

    }

}