Routing, as we saw, is the mapping of HTTP requests to Scala handlers. Routes are stored in conf/routes. A route is defined by an HTTP verb, followed by the end-point, followed by a Scala function:

// verb   // end-point              // Scala handler
GET       /                         controllers.Application.index

We learnt to add new routes by just adding lines to the routes file. We are not limited to static routes, however. The Play framework lets us include wild cards in routes. The value of the wild card can be passed as an argument to the controller. To see how this works, let's create a controller that takes the name of a person as argument. In the Application object in app.controllers, add:

// app/controllers/Application.scala

class Application extends Controller {

  ...

  def hello(name:String) = Action {
    Ok(s"hello, $name")
  }
}

We can now define a route handled by this controller:

// conf/routes
GET  /hello/:name             controllers.Application.hello(name)

If you now point your browser to 127.0.0.1:9000/hello/Jim, you will see hello, Jim appear on the screen.

Any string between : and the following / is treated as a wild card: it will match any combination of characters. The value of the wild card can be passed to the controller. Note that the wild card can appear anywhere in the URL, and there can be more than one wild card. The following are all valid route definitions, for instance:

GET /hello/person-:name        controllers.Application.hello(name)
// ... matches /hello/person-Jim

GET /hello/:name/picture  controllers.Application.pictureFor(name)
// ... matches /hello/Jim/picture

GET /hello/:first/:last controllers.Application.hello(first, last)
// ... matches /hello/john/doe

There are many other options for selecting routes and passing arguments to the controller. Consult the documentation for the Play framework for a full discussion on the routing possibilities: https://www.playframework.com/documentation/2.4.x/ScalaRouting.