This chapter walked you through some techniques to help you with developing applications where you need to specify the content type definition and make sure that the server is prepared to handle different content mime types. If it is not supported, at least you know how to set the correct an HTTP status code, should it be retrieved by the requester.
You also had the opportunity to apply XML and JSON object conversions, as well as including HAL in the order-api application.
The next Chapter 8, Working with Databases and ODMs, is going to go a little bit further and replace our in-memory storage with MongoDB.