In some submissions you are required to build a web application that uses a RESTful web service.
Spark is a small and simple framework for building web services in Java. A quick start guide for getting started can be found here.
Spring is a larger and more powerful framework for web services in Java. A guide for creating a new RESTful web service can be found here and a guide for how to access it using jQuery can be found here.
You are free to use any other framework you like for the programming language you choose to use for the assignments.