Elixir JSON Schema validator

Build Status

A JSON Schema validator with full support for the draft 4 specification. Passes the official JSON Schema Test Suite (with the exception of the optional/format tests for now).

Usage

Configuration

If you have remote schemata that need to be fetched at runtime, you have to register a function that takes a URL and returns a Map of the parsed JSON. So in your Mix config file you should have something like this:

config :ex_json_schema,

  :remote_schema_resolver,

  fn url -> HTTPoison.get!(url).body |> Poison.decode! end

You do not have to do that for the official draft 4 meta-schema found at http://json-schema.org/draft-04/schema# though. That schema is bundled with the project and will work out of the box without any network calls.

Resolving a schema

In this step the schema is validated against its meta-schema (the draft 4 schema definition) and $refs are being resolved (making sure that the reference points to an existing fragment). You should only resolve a schema once to avoid the overhead of resolving it in every validation call.

iex> schema = %{

  "type" => "object",

  "properties" => %{

    "foo" => %{

      "type" => "string"

    }

  }

} |> ExJsonSchema.Schema.resolve

Note that Map keys are expected to be strings, since in practice that data will always come from some JSON parser.

Validation

If you're only interested in whether a piece of data is valid according to the schema:

iex> ExJsonSchema.Validator.valid?(schema, %{"foo" => "bar"})

true



iex> ExJsonSchema.Validator.valid?(schema, %{"foo" => 1})

false

Or in case you want to have detailed validation errors:

iex> ExJsonSchema.Validator.validate(schema, %{"foo" => "bar"})

:ok



iex> ExJsonSchema.Validator.validate(schema, %{"foo" => 1})

{:error, [{"Type mismatch. Expected String but got Integer.", "#/foo"}]}

Errors are tuples of a message and the path to the element not matching the schema. The path is following the same conventions used in JSON Schema for referencing JSON elements.

License

Released under the MIT license.

TODO