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jsonhttpelixirplug

Access result of Elixir Plug.Parsers.JSON

I am writing a small http server using Elixir Plug and having some trouble understanding how its parser works. I cannot figure out how to access the result of the parser in my router. I currently have 

...
plug Plug.Parsers, parsers: [:json],
                json_decoder: Poison
plug :match
plug :dispatch
forward "/admin" , to: VoucherSite.Admin.AdminRouter
...

And in the admin router I want to access the parsed result from the Parser called above

put "/user" do
  ...access result here...
  respond(conn, {:ok, ""})
end

It feels like I am missing something obvious but all I have access to is conn which is the connection so no idea how to get the parsed body from the request.

Solution

  • Plug is a behaviour, having 2 callbacks: init/1 and call/2. The latter receives a Plug.Conn struct and returns possibly modified Plug.Conn struct. That allows to chain plugs.

    %Plug.Conn{assigns} is intended to be used to update the map between calls to different plugs.

    Plug.Conn implements the Inspect algebra out of the box, so just do:

    Logger.debug inspect(conn)

    somewhere and you’ll see where the parser stores the body (I would bet it’s some key in the assigns map.)