Using the changed Embedded Container Configuration 

EmbeddedServletContainer is changed to WebServer. Also, the org.springframework.boot.context.embedded package is refactored to org.springframework.boot.web.embedded. If TomcatEmbeddedServletContainerFactory was used to configure an embedded Tomcat with a custom port in an application as in the following, then it will need to be changed:

@Bean
public EmbeddedServletContainerFactory servletContainer() {
 TomcatEmbeddedServletContainerFactory tomcat = new TomcatEmbeddedServletContainerFactory();
 Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol");
 connector.setScheme("http");
 connector.setPort(9090); 
 tomcat.addAdditionalTomcatConnectors(connector);
 return tomcat;
}

It must be changed to use TomcatServletWebServerFactory instead, as in the following:

@Bean
public TomcatServletWebServerFactory webServer() {
    TomcatServletWebServerFactory tomcat = new 
    TomcatServletWebServerFactory(9090);
    return tomcat;
}