Now that we have learned about the importance of validation and the flexibility of joi, let's look at where we can apply it in our hapi applications. Fortunately, hapi provides first class support for validation on its route configuration objects. We saw this very briefly in Chapter 2, Adding Functionality by Routing Requests, both on a route configuration object and where the validation steps take place within the request life cycle.
On a route configuration object, we can provide validation rules through a validate object. With this, we can define specific validation rules for the request headers, parameters, query, payload, and also on the response. It might not be immediately obvious why we would validate our response, but we'll look at that further on in the chapter. Let's first look at an example of a route configuration with added validation rules.
Let's take our user store application from the previous chapters, and add some validation. If you remember...