defmodule Example.Router do
use Plug.Router
plug :match
plug :dispatch
get "/" do
send_resp(conn, 200, "Welcome")
end
match _ do
send_resp(conn, 404, "Oops!")
end
end
以上是一个最基本的路由器，但是整段代码应该来说还是容易理解的。我们通过 use Plug.Router 引用了一个宏，并配置了两个内置的 Plugs：:match 和 :dispatch。然后定义了两个路由，一个处理根目录的 GET 请求，第二个匹配了其它所有的请求并返回 404 消息。
我们需要回到 lib/example/application.ex 文件，把 Example.Router 添加到 web 服务器的 supervisor tree 当中。把 Example.HelloWorldPlug 替换为新的路由：
def start(_type, _args) do
children = [
{Plug.Cowboy, scheme: :http, plug: Example.Router, options: [port: 8080]}
]
opts = [strategy: :one_for_one, name: Example.Supervisor]
Logger.info("Starting application...")
Supervisor.start_link(children, opts)
end
defmodule Example.Plug.VerifyRequest do
defmodule IncompleteRequestError do
@moduledoc """
Error raised when a required field is missing.
"""
defexception message: ""
end
def init(options), do: options
def call(%Plug.Conn{request_path: path} = conn, opts) do
if path in opts[:paths], do: verify_request!(conn.params, opts[:fields])
conn
end
defp verify_request!(params, fields) do
verified =
params
|> Map.keys()
|> contains_fields?(fields)
unless verified, do: raise(IncompleteRequestError)
end
defp contains_fields?(keys, fields), do: Enum.all?(fields, &(&1 in keys))
end
defmodule Example.Router do
use Plug.Router
alias Example.Plug.VerifyRequest
plug Plug.Parsers, parsers: [:urlencoded, :multipart]
plug VerifyRequest, fields: ["content", "mimetype"], paths: ["/upload"]
plug :match
plug :dispatch
get "/" do
send_resp(conn, 200, "Welcome")
end
get "/upload" do
send_resp(conn, 201, "Uploaded")
end
match _ do
send_resp(conn, 404, "Oops!")
end
end
defmodule Example.Application do
use Application
require Logger
def start(_type, _args) do
children = [
{Plug.Cowboy, scheme: :http, plug: Example.Router, options: [port: cowboy_port()]}
]
opts = [strategy: :one_for_one, name: Example.Supervisor]
Logger.info("Starting application...")
Supervisor.start_link(children, opts)
end
defp cowboy_port, do: Application.get_env(:example, :cowboy_port, 8080)
end
Application.get_env 的第三个参数是默认值，当配置不存在的时候采用。
我们可以通过下面的命令来启动应用：
$ mix run --no-halt
测试 Plug
借助 Plug.Test 我们可以很直观地测试 Plug。该模块包括了许多方便测试的函数。
把下面这段路由测试代码写到 test/example/router_test.exs：
defmodule Example.RouterTest do
use ExUnit.Case
use Plug.Test
alias Example.Router
@content "<html><body>Hi!</body></html>"
@mimetype "text/html"
@opts Router.init([])
test "returns welcome" do
conn =
:get
|> conn("/", "")
|> Router.call(@opts)
assert conn.state == :sent
assert conn.status == 200
end
test "returns uploaded" do
conn =
:get
|> conn("/upload?content=#{@content}&mimetype=#{@mimetype}")
|> Router.call(@opts)
assert conn.state == :sent
assert conn.status == 201
end
test "returns 404" do
conn =
:get
|> conn("/missing", "")
|> Router.call(@opts)
assert conn.state == :sent
assert conn.status == 404
end
end
运行以下的命令进行测试：
$ mix test test/example/router_test.exs
Plug.ErrorHandler
defmodule Example.Router do
use Plug.Router
use Plug.ErrorHandler
alias Example.Plug.VerifyRequest
plug Plug.Parsers, parsers: [:urlencoded, :multipart]
plug VerifyRequest, fields: ["content", "mimetype"], paths: ["/upload"]
plug :match
plug :dispatch
get "/" do
send_resp(conn, 200, "Welcome")
end
get "/upload" do
send_resp(conn, 201, "Uploaded")
end
match _ do
send_resp(conn, 404, "Oops!")
end
defp handle_errors(conn, %{kind: kind, reason: reason, stack: stack}) do
IO.inspect(kind, label: :kind)
IO.inspect(reason, label: :reason)
IO.inspect(stack, label: :stack)
send_resp(conn, conn.status, "Something went wrong")
end
end