This implementation of the Todo-Backend API is running on the Java EE 8 compatible Payara Micro as a microservice. The Maven deps are quite simple and only the built war is needed to be passed to the imbedded server in the Procfile to run.
It's live at https://javaeetodo.herokuapp.com/todo.
You can play with it here.
One can also run the tests to make sure it's compliant with the Todo-Backend specs.