updated error code.

docs/guide/rest.md

@@ -144,17 +144,20 @@ HTTP Status Code Summary
 ------------------------
 
 * `200`: OK. Everything worked as expected.
-* `201`: A data item was successfully created. Please check the `Location` header for the URL to access the new data item.
-* `204`: A data item was successfully deleted.
-* `304`: Data not modified. You can use cached data.
-* `400`: Bad request. This could be caused by various reasons from the user side, such as invalid content type request,
-  invalid API version number, or data validation failure. If it is data validation failure, please check
-  the response body for error messages.
+* `201`: A resource was successfully created in response to a `POST` request. The `Location` header
+   contains the URL pointing to the newly created resource.
+* `204`: The request is handled successfully and the response contains no body content (like a `DELETE` request).
+* `304`: Resource was not modified. You can use the cached version.
+* `400`: Bad request. This could be caused by various reasons from the user side, such as invalid JSON
+   data in the request body, invalid action parameters, etc.
 * `401`: No valid API access token is provided.
 * `403`: The authenticated user is not allowed to access the specified API endpoint.
-* `404`: The requested item does not exist.
+* `404`: The requested resource does not exist.
 * `405`: Method not allowed. Please check the `Allow` header for allowed HTTP methods.
-* `500`: Internal server error.
+* `415`: Unsupported media type. The requested content type or version number is invalid.
+* `422`: Data validation failed (in response to a `POST` request, for example). Please check the response body for detailed error messages.
+* `429`: Too many requests. The request is rejected due to rate limiting.
+* `500`: Internal server error. This could be caused by internal program errors.
 
 
 Data Formatting

framework/rest/Controller.php

@@ -8,9 +8,9 @@
 namespace yii\rest;
 
 use Yii;
-use yii\web\BadRequestHttpException;
 use yii\web\Response;
 use yii\web\UnauthorizedHttpException;
+use yii\web\UnsupportedMediaTypeHttpException;
 use yii\web\VerbFilter;
 
 /**
@@ -124,7 +124,7 @@ class Controller extends \yii\web\Controller
 
 	/**
 	 * Resolves the response format and the API version number.
-	 * @throws BadRequestHttpException
+	 * @throws UnsupportedMediaTypeHttpException
 	 */
 	protected function resolveFormatAndVersion()
 	{
@@ -142,7 +142,7 @@ class Controller extends \yii\web\Controller
 					if (in_array($params[self::HEADER_VERSION], $this->supportedVersions, true)) {
 						$this->version = $params[self::HEADER_VERSION];
 					} else {
-						throw new BadRequestHttpException('You are requesting an invalid version number.');
+						throw new UnsupportedMediaTypeHttpException('You are requesting an invalid version number.');
 					}
 				}
 				return;
@@ -150,7 +150,7 @@ class Controller extends \yii\web\Controller
 		}
 
 		if (!isset($types['*/*'])) {
-			throw new BadRequestHttpException('None of your requested content types is valid.');
+			throw new UnsupportedMediaTypeHttpException('None of your requested content types is supported.');
 		}
 	}
 

framework/rest/Serializer.php

@@ -126,7 +126,7 @@ class Serializer extends Component
 	 */
 	protected function serializeModelErrors($model)
 	{
-		$this->response->setStatusCode(400, 'Data Validation Failure');
+		$this->response->setStatusCode(422, 'Data Validation Failed.');
 		$result = [];
 		foreach ($model->getFirstErrors() as $name => $message) {
 			$result[] = [