How do I change the default jetty port using dockerized jetty

I am running jetty from a docker-composer.yml file. I had changed the port mapping like this:

services:
  web:
    image: jetty
    ports:
     - "8000:8000"

This does not change the port that jetty starts up on. How do I go about doing this from a dockerized jetty?

By default jetty runs on port 8080. So you compose file should be

services:
  web:
    image: jetty
    ports:
     - "8000:8080"

This maps port 8080 from inside the container to port 8000 on your host. Though you should not need to run jetty on port 80 inside the container. But if you still need to for some reason then you need to use the jetty config options using JAVA_OPTIONS

services:
  web:
    image: jetty
    environment:
      JAVA_OPTIONS: "-Djetty.port=80"
    ports:
     - "8000:80"

So port 80 inside the container and port 8000 on your host machine.