Make sure you have Java and Maven installed. Also, install the Heroku CLI.

$ mvn install
$ heroku local:start

Your app should now be running on localhost:5000.

If you're going to use a database, ensure you have a local .env file that reads something like this:

JDBC_DATABASE_URL=jdbc:postgresql://localhost:5432/chatdb

and run PostgreSQL like this:

docker run --name chat-postgres -p 5432:5432 -e POSTGRES_HOST_AUTH_METHOD=trust -e POSTGRES_DB=chatdb -d postgres:13

$ heroku create
$ git push heroku main
$ heroku open