While discussing the JAX-RS APIs in the previous chapter, we covered the resource class and the resource class methods in RESTful web APIs. If you need a quick brush-up on this topic, refer to the Annotations for defining a RESTful resource section in Chapter 3, Introducing the JAX-RS API. In this section, you will get introduced to two new concepts, namely subresources and subresource locators in REST. You will find them very useful while designing well-structured RESTful web APIs.