RequestValidator

A blazing fast request validator for your phoenix app, which validates a request body before hitting the request handler in the controller.

• Why RequestValidator
• Installation
• Usage
• Ecto Support
• Custom Validation Rules

Why RequestValidator

It's common for a web service to validate incoming data. The most common layer where this is done is at the controller level and this sometimes leads to having a bloated controller. But with RequestValidator, you move the validation logic to a layer just before the controller and your controller is now free from doing validation.

Installation

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

def deps do
  [
    {:request_validator, "~> 0.8.5"}
  ]
end

Usage

First of all, you need to define a validation schema to be used against the incoming data.

defmodule App.Requests.Registration do
  use Request.Validator
  
  # Get the validation rules that apply to the incoming request.
  @impl Request.Validator
  def rules(_) do
    [
      email: ~w[required email]a,
      first_name: ~w[required string]a,
      last_name: ~w[required string]a,
      password: [:required, :string, {:min, 8}, :confirmed]
    ]
  end

  # Determine if the user is authorized to make this request.
  @impl Request.Validator
  def authorize(_), do: true
end

The above validation schema can now be used;

defmodule App.UserController do
  use AppWeb, :controller

  plug Request.Validator.Plug,
    register: App.Requests.Registration

  def register(conn, params) do
    case App.UserService.create(params) do
      :ok ->
        conn
        |> put_status(201)
        |> json(%{message: "Account created successfully"})
      {:error, msg} ->
        conn
        |> put_status(500)
        |> json(%{message: msg})
    end
  end
end

As you can see in the controller, the register handler does not need to worry about validating the incoming request because RequestValidator will handle that automatically and send the right response if the request fails validation based on the given validation schema.

You can specify validation schema for each of the handlers in a controller:

defmodule App.UserController do
  use AppWeb, :controller

  plug Request.Validator.Plug,
    login: App.Requests.Login,
    register: App.Requests.Registration

  ...
end

Full documentation can be found at https://hexdocs.pm/request_validator.

Ecto Support

In some cases, your application already makes use of the ecto library. I'm glad to tell you that this library has support when the rule method returns an Ecto.Changeset struct so that you can make use of the advantages provided by this library without rewriting your validation logic. See the example below:

defmodule App.SomeEctoSchema do
  use Ecto.Schema
  import Ecto.Changeset

  embedded_schema do
    field(:name, :string)
    field(:email, :string)
    field(:age, :integer)
    field(:password, :string)
  end

  @doc false
  def changeset(attrs), do: changeset(%__MODULE__{}, attrs)

  @doc false
  def changeset(struct, attrs) do
    struct
    |> cast(attrs, [:name, :email, :age, :password])
    |> validate_required([:name, :email, :age, :password])
    |> validate_number(:age, less_than_or_equal_to: 32)
  end
end

defmodule App.Requests.TestRequest do
  use Request.Validator

  alias App.SomeEctoSchema

  @impl Request.Validator
  def rules(conn), do: SomeEctoSchema.changeset(conn.params)

  @impl Request.Validator
  def authorize(_), do: true
end

Custom Validation Rules

This library provides a variety of helpful rules, however, you might want to define some rules to house your validation logic. To achieve this, you need to create your own rules module, extend the default rules and update the library configuration;

defmodule App.Validation.Rules do
  use Request.Validator.Rules # grab default rules provided by the library

  @spec uppercase(binary(), keyword()) :: :ok | {:error, binary()}
  def uppercase(value, fields: _fields, field: _field) do
    case String.upcase(value) do
      ^value ->
        :ok
      _ ->
        {:error, "This field must be uppercase."}
    end
  end
end

After defining a module with your custom rules, you will need to update your application configuration:

config :request_validator, rules_module: App.Validation.Rules

Once the new rule has been added and configuration updated, it can now be used:

# ...
  def rules(_) do
    [
      name: ~w[required string uppercase]a
    ]
  end
# ...

Note that if your rule accepts options/parameters, its function definition should have an arity of 3, and the second argument will be the option provided when the rule is used, ex: {:custom_rule, options}

Available Rules

active_url

The field under validation must have a valid AAAA or A record. This check is done using :inet.gethostbyname

alpha_dash

The field under validation may have alpha-numeric characters, as well as dashes and underscores

boolean

The field under validation must be able to be cast as a boolean. Accepted input are true, false, 1, 0, "1", and "0".

confirmed

The field under validation must have a matching field of {field}_confirmation. For example, if the field under validation is password, a matching password_confirmation field must be present in the input.

email

The field under validation must be a valid email. This rule utilizes the email_checker library. By default it checks for email format and mx record to make sure the email does exists.

{exists, callback}

The field under validation must exist in a datastore. See sample usage below:

reference: [:required, :alpha_dash, min(2), max(20), {:exists, &reference_exists?/2}]
# ...
defp reference_exists?(tx_no, _opts) do
  Payments.get_by_reference(tx_no))
end

file

The field under validation must be a successfully uploaded file by checking if the field is a Plug.Upload struct.

{gt, field}

The field under validation must be greater than the given field. The two fields must be of the same type. Strings, numerics and lists are evaluated using the same conventions as the size rule.

investment: [:required, :numeric],
return_on_investment: [:required, {:gt, :investment}]

{in_list, options}

The field under validation must be included in the given list of values.

region: [:required, {:in_list, ~w[us-east-2 us-east-1 us-west-1 us-west-2]}]

list

The field under validation must be an Elixir list.

{lt, field}

The field under validation must be less than the given field. The two fields must be of the same type. Strings, numerics and lists are evaluated using the same conventions as the size rule.

estimated_churn_rate: [:required, :numeric],
churn_rate: [:required, {:lt, :estimated_churn_rate}]

map

The field under validation must be an Elixir map.

{max, value}

The field under validation must be less than or equal to a maximum value. Strings, numerics and lists are evaluated in the same fashion as the size rule.

{min, value}

The field under validation must have a minimum value. Strings, numerics and lists are evaluated in the same fashion as the size rule.

numeric

The field under validation must be numeric based on is_number.

required

The field under validation must be present in the input data and not empty. A field is considered "empty" if one of the following conditions are true:

• The value is null.
• The value is an empty string.
• The value is an empty list or map.

{size, value}

The field under validation must have a size matching the given value.

# Validate that a string is exactly 12 characters long...
title: [{:size, 12}]

# Validate that a provided integer equals 10...
seats: [:numeric, {:size, 10}]

# Validate that an list has exactly 5 elements...
tags: [:list, {:size, 5}]

string

The field under validation must be a string.

{unique, callback}

The field under validation must not exist within the a datastore. See sample usage below:

username: [:required, :alpha_dash, min(2), max(20), {:unique, &is_unique_username?/2}]
# ...
defp is_unique_username?(username, _opts) do
  is_nil(Accounts.get_user_by_username(username))
end

url

The field under validation must be a valid URL.

Helper Functions

See content.

Validating Nested Input

Validating nested map input shouldn't be a problem. For example the HTTP request contains address field which is a map with nested attributes (line1, line2...), you may validate it like so:

address: map(
  line1: [:required, :string, {:max, 100}],
  city: [:required, :string, {:max, 50}],
  zip_code: [:required, :string, {:max, 10}],
  country: [:required, :string, {:max, 60}],
  line2: [:string, {:max, 100}],
  state: [:string, {:max, 50}]
)

TODOS

• Include more validation rules
• Norm validation support
• Ecto schema support

License

RequestValidator is released under the MIT License - see the LICENSE file.