# `Oasis.Plug.RequestValidator`
[🔗](https://github.com/xinz/oasis/blob/main/lib/oasis/plug/request_validator.ex#L1)

A plug to convert types and validate the HTTP request parameters by the schemas of
the OpenAPI definition.

The schema options can be found in the generated `pre-` plug handler file, the full list:

  * `:query_schema`
  * `:header_schema`
  * `:cookie_schema`
  * `:body_schema`

All of these options are fully map and generated from the corresponding definition of the OpenAPI Specification.

When the query parameters are verified by the validation of `:query_schema`, the coverted types of query parameters
are reserved in `:query_params` and `:params` field of the `Plug.Conn`.

When the header parameters are verified by the validation of `:header_schema`, the converted types of header parameters
are reserved in `:req_headers` field of the `Plug.Conn`.

When the cookie parameters are verified by the validation of `:cookie_schema`, the coverted types of cookie parameters
are reserved in `:req_cookies` field of the `Plug.Conn`.

When the request body is verified by the validation of `:body_schema`, the coverted types of request body are reserved
in `:body_params` and `:params` field of the `Plug.Conn`.

## Primitive JSON bodies

Oasis follows Plug's default `nest_all_json: false` behavior: Plug wraps
non-object JSON roots in a single `_json` key and leaves object roots as direct
maps. That representation is otherwise indistinguishable from a literal JSON
object whose only property is named `_json`, so Oasis only unwraps it when
raw-body provenance proves that the wire value was not an object. Generated
routers configure the required reader automatically. Handwritten pipelines
that accept JSON bodies must configure `Plug.Parsers` in the same way and keep
the default `nest_all_json: false` setting:

    plug Plug.Parsers,
      parsers: [:json],
      pass: ["*/*"],
      json_decoder: Jason,
      body_reader: {Oasis.CacheRawBodyReader, :read_body, []}

    plug Oasis.Plug.RequestValidator, body_schema: body_schema

Without that provenance, Oasis deliberately keeps the `_json` map intact and
fails closed rather than guessing from the schema and potentially accepting a
literal object as a primitive value. An empty parsed map is also ambiguous—it
may represent either an absent body or the JSON object `{}`—so Oasis returns
an actionable 415 unless framing headers prove that bytes were present. After
successful validation, primitive roots remain available as
`conn.body_params["_json"]` so Plug's `body_params` and `params` fields stay
map-shaped.

# `call`

# `init`

---

*Consult [api-reference.md](api-reference.md) for complete listing*