NifXsdValidate

An elixir package for validating xml content against xsd, based on libxml2. It is basically meant to preload xsd schemata from given urls and use those throughout the lifetime of an application. The validation returns the status and the error reason as a list of strings.

Installation

Although it would be probably possible to make this work it won't currently compile for windows.

Prerequisites for building:

• curl
• build tools (gcc, make, ...)

The package can be installed by adding nif_xsd_validate to the list of dependencies in mix.exs:

def deps do
  [
    {:nif_xsd_validate, git: "https://github.com/terminalstatic/nif_xsd_validate"}
  ]
end

Get the dependencies:

mix deps.get

This is how to update the package:

  mix deps.update nif_xsd_validate
  mix deps.compile nif_xsd_validate

Usage

Initialize the schema agent in the application module or in the code. Schemata (Libxml2 xmlSchemaPtrs) are stored in a map and identified by a key.

NifXsd.Schema.start_link(%{someSchemaKey1: "url://to/schema1"})
NifXsd.validate(NifXsd.Schema.get(:someSchemaKey1), "<xml></xml>")

Supervisor configuration example:

children = [
supervisor(NifXsd.Schema,[%{someSchemaKey1: "url://to/schema1", someSchemaKey2: "url://to/schema2"]})
]

Validation works as expected:

NifXsd.validate(NifXsd.Schema.get(:someSchemaKey1), "<xml></xml>")
NifXsd.validate(NifXsd.Schema.get(:someSchemaKey2), "<xml></xml>")

Plug example

It comes in quite handy when used in combination with Plug, a quick example could look like this:

defmodule ExamplePlug.XsdValidate do
    import Plug.Conn
    def init(default), do: default
  
    def call(conn, _) do
        {:ok, body, conn} = Plug.Conn.read_body(conn)    
        
        case NifXsd.validate(NifXsd.Schema.get(:schema), body) do
            :ok -> conn |> assign(:xml_body, body)
            {:error, reason} -> 
            reason = 
            "<Errors>" 
            <> (reason
            |>Enum.map(fn(x) -> "<Error>" <> x <> "</Error>" end)
            |>Enum.join)
            <>"</Errors>"
            conn
            |> put_resp_content_type("text/xml")
            |> send_resp(400, reason)
            |> halt
        end
    end
end