Understanding Plug.Router

Now that we know how a Plug module works, let’s leverage one of the predefined plugs, Plug.Router, to add functionality to our HTTP server. At the end of Chapter 2, we saw that to use our HTTP server for a proper REST API, we need a way to route incoming requests based on different paths and HTTP verbs. Cowboy has an internal way of routing the requests, but Plug.Router allows us to do that in a very simple DSL. Another advantage of using Plug.Router to route our requests, instead of using Cowboy directly, is that we can start using plugs earlier in our request-response cycle, even before they get to Cowboy. Here, we can only rely on Cowboy to send a response.

So, let’s start by defining a new plug, ExampleRouter:

example_router.exs

Mix.install([
  {:plug_cowboy, "~> 2.0"}
])
defmodule ExampleRouter do
  use Plug.Router
  plug :match
  plug :dispatch
  get "/greet&quot...