Fix jakartaee#336 - expand list of supported HTTP status codes

Adds 308, 421, 422, 426

Author: markt-asf

api/src/main/java/jakarta/servlet/http/HttpServletResponse.java

@@ -499,6 +499,12 @@ default public Supplier<Map<String, String>> getTrailerFields() {
      */
     public static final int SC_TEMPORARY_REDIRECT = 307;
 
+    /**
+     * Status code (308) indicating that the requested resource resides permanently under a different URI. The new URI
+     * <em>SHOULD</em> be given by the <code><em>Location</em></code> field in the response.
+     */
+    public static final int SC_PERMANENT_REDIRECT = 308;
+
     /**
      * Status code (400) indicating the request sent by the client was syntactically incorrect.
      */
@@ -599,6 +605,25 @@ default public Supplier<Map<String, String>> getTrailerFields() {
      */
     public static final int SC_EXPECTATION_FAILED = 417;
 
+    /**
+     * Status code (421) indicating that the server is unwilling or unable to produce an authoritative response for the
+     * target URI.
+     */
+    public static final int SC_MISDIRECTED_REQUEST = 421;
+
+    /**
+     * Status code (422) indicating that the server understands the content type of the request but is unable to process the
+     * contained instructions.
+     */
+    public static final int SC_UNPROCESSABLE_CONTENT = 422;
+
+    /**
+     * Status code (426) indicating that the server refuses to perform the request using the current protocol but may be
+     * willing to do so after the client upgrades to a different protocol. The server must include an appropriate
+     * {@code Upgrade} header in the response.
+     */
+    public static final int SC_UPGRADE_REQUIRED = 426;
+
     /**
      * Status code (500) indicating an error inside the HTTP server which prevented it from fulfilling the request.
      */

spec/src/main/asciidoc/servlet-spec-body.adoc

@@ -8573,6 +8573,10 @@ Clarify the behaviour of `getDateHeader()` and `getIntHeader()` when multiple
 headers with the same name are present in the `HttpServletRequest`. The expected
 behaviour is aligned with `getHeader()`. 
 
+link:https://github.com/eclipse-ee4j/servlet-api/issues/336[Issue 336]::
+Add new constants to `HttpServletResponse` for the HTTP response codes 308, 421,
+422 and 426.
+
 link:https://github.com/eclipse-ee4j/servlet-api/issues/415[Issue 415]::
 Add overloaded `setCharacterEncoding()` methods that support `Charset`.