Code works with Embedded Apache Tomcat 8 but not with 9. What's changed?

Question

Embedding Apache Tomcat into an eclipse web app project.
The code works when I'm using the latest Tomcat 8 (8.0.5 Embedded) jars as dependencies, and this server responds at http://localhost:8080, however, it fails to start the same way and does not respond in this address when using the latest Tomcat 9's (9.0.5 Embedded) jars.
The code is very simple. I've researched as thoroughly as I could but didn't figure out what's wrong.

package app;

import org.apache.catalina.LifecycleException;
import org.apache.catalina.startup.Tomcat;

public class Main {

    public static void main(String[] args) {

        Tomcat tomcat = new Tomcat();
        tomcat.setPort(8080);

        try {
            tomcat.start();
        } catch (LifecycleException e) {
            e.printStackTrace();
        }

        tomcat.getServer().await();
    }

}

console output when using Tomcat 9.0.5 Embedded jars:

org.apache.catalina.core.StandardService startInternal
INFO: Starting service [Tomcat]

console output when using Tomcat 8.0.5 Embedded jars:

org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-nio-8080"]
org.apache.tomcat.util.net.NioSelectorPool getSharedSelector
INFO: Using a shared selector for servlet write/read
org.apache.catalina.core.StandardService startInternal
INFO: Starting service Tomcat
org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["http-nio-8080"]

Answer 1

It looks like you haven't added a Connector to your embedded server. Tomcat 9 no longer automatically adds a Connector to your server for you, so you'll have to trigger it yourself:

package app;

import org.apache.catalina.LifecycleException;
import org.apache.catalina.startup.Tomcat;

public class Main {

    public static void main(String[] args) {

        Tomcat tomcat = new Tomcat();
        tomcat.setPort(8080);
        tomcat.getConnector(); // Trigger the creation of the default connector

        try {
            tomcat.start();
        } catch (LifecycleException e) {
            e.printStackTrace();
        }

        tomcat.getServer().await();
    }
}

It's worth mentioning that adding a call to tomcat.getConnector() should be safe for previous versions of Tomcat as well, so this need not be a "Tomcat 9-only" thing.