Add docs for API version deprecation support

Closes gh-35049

framework-docs/modules/ROOT/pages/web/webflux-versioning.adoc

@@ -79,6 +79,20 @@ You can also specify a default version to use.
 
 
 
+[[webflux-versioning-deprecation-handler]]
+== ApiVersionDeprecationHandler
+[.small]#xref:web/webmvc-versioning.adoc#mvc-versioning-deprecation-handler[See equivalent in the Reactive stack]#
+
+This strategy can be configured to send hints and information about deprecated versions to
+clients via response headers. The built-in `StandardApiVersionDeprecationHandler`
+can set the "Deprecation" "Sunset" headers and "Link" headers as defined in
+https://datatracker.ietf.org/doc/html/rfc9745[RFC 9745] and
+https://datatracker.ietf.org/doc/html/rfc8594[RFC 8594]. You can also configure a custom
+handler for different headers.
+
+
+
+
 [[webflux-versioning-mapping]]
 == Request Mapping
 [.small]#xref:web/webmvc-versioning.adoc#mvc-versioning-mapping[See equivalent in the Servlet stack]#

framework-docs/modules/ROOT/pages/web/webflux/config.adoc

@@ -690,7 +690,7 @@ reliance on it.
 == API Version
 [.small]#xref:web/webmvc/mvc-config/api-version.adoc[See equivalent in the Servlet stack]#
 
-To enable API versioning with a request header, use the following:
+To enable API versioning, use the `ApiVersionConfigurer` callback of `WebFluxConfigurer`:
 
 [tabs]
 ======
@@ -722,19 +722,30 @@ Kotlin::
 ----
 ======
 
-Alternatively, the version can be resolved from a request parameter, from a path segment,
-or  through a custom `ApiVersionResolver`.
+You can resolve the version through one of the built-in options listed below, or
+alternatively use a custom `ApiVersionResolver`:
+
+- Request header
+- Request parameter
+- Path segment
+- Media type parameter
 
 TIP: When using a path segment, consider configuring a shared path prefix externally
 in xref:web/webmvc/mvc-config/path-matching.adoc[Path Matching] options.
 
-Raw version values are parsed with `SemanticVersionParser` by default, but you can use
+By default, the version is parsed with `SemanticVersionParser`, but you can also configure
 a custom xref:web/webflux-versioning.adoc#webflux-versioning-parser[ApiVersionParser].
 
-"Supported" versions are transparently detected from versions declared in request mappings
-for convenience, but you can turn that off through a flag in the WebFlux config, and use only
-the versions configured explicitly in the config. Requests with a version that is not
-supported are rejected with `InvalidApiVersionException` resulting in a 400 response.
+Supported versions are transparently detected from versions declared in request mappings
+for convenience, but you can turn that off through a flag in the WebFlux config, and
+consider only the versions configured explicitly in the config as supported.
+Requests with a version that is not supported are rejected with
+`InvalidApiVersionException` resulting in a 400 response.
+
+You can set an `ApiVersionDeprecationHandler` to send information about deprecated
+versions to clients. The built-in standard handler can set "Deprecation", "Sunset", and
+"Link" headers based on https://datatracker.ietf.org/doc/html/rfc9745[RFC 9745] and
+https://datatracker.ietf.org/doc/html/rfc8594[RFC 8594].
 
 Once API versioning is configured, you can begin to map requests to
 xref:web/webflux/controller/ann-requestmapping.adoc#webflux-ann-requestmapping-version[controller methods]

framework-docs/modules/ROOT/pages/web/webmvc-versioning.adoc

@@ -30,6 +30,7 @@ related to versioning. It does the following:
 - Resolves versions from the requests via xref:#mvc-versioning-resolver[ApiVersionResolver]
 - Parses raw version values into `Comparable<?>` with an xref:#mvc-versioning-parser[ApiVersionParser]
 - xref:#mvc-versioning-validation[Validates] request versions
+- Sends deprecation hints in the responses
 
 `ApiVersionStrategy` helps to map requests to `@RequestMapping` controller methods,
 and is initialized by the MVC config. Typically, applications do not interact
@@ -40,7 +41,7 @@ directly with it.
 
 [[mvc-versioning-resolver]]
 == ApiVersionResolver
-[.small]#xref:web/webmvc-versioning.adoc#mvc-versioning-resolver[See equivalent in the Reactive stack]#
+[.small]#xref:web/webflux-versioning.adoc#webflux-versioning-resolver[See equivalent in the Reactive stack]#
 
 This strategy resolves the API version from a request. The MVC config provides built-in
 options to resolve from a header, from a request parameter, or from the URL path.
@@ -78,6 +79,20 @@ You can also specify a default version to use.
 
 
 
+[[mvc-versioning-deprecation-handler]]
+== ApiVersionDeprecationHandler
+[.small]#xref:web/webflux-versioning.adoc#webflux-versioning-deprecation-handler[See equivalent in the Reactive stack]#
+
+This strategy can be configured to send hints and information about deprecated versions to
+clients via response headers. The built-in `StandardApiVersionDeprecationHandler`
+can set the "Deprecation" "Sunset" headers and "Link" headers as defined in
+https://datatracker.ietf.org/doc/html/rfc9745[RFC 9745] and
+https://datatracker.ietf.org/doc/html/rfc8594[RFC 8594]. You can also configure a custom
+handler for different headers.
+
+
+
+
 [[mvc-versioning-mapping]]
 == Request Mapping
 [.small]#xref:web/webflux-versioning.adoc#webflux-versioning-mapping[See equivalent in the Reactive stack]#

framework-docs/modules/ROOT/pages/web/webmvc/mvc-config/api-version.adoc

@@ -3,23 +3,34 @@
 
 [.small]#xref:web/webflux/config.adoc#webflux-config-api-version[See equivalent in the Reactive stack]#
 
-To enable API versioning with a request header, use the following:
+To enable API versioning, use the `ApiVersionConfigurer` callback of `WebMvcConfigurer`:
 
 include-code::./WebConfiguration[tag=snippet,indent=0]
 
-Alternatively, the version can be resolved from a request parameter, from a path segment,
-or  through a custom `ApiVersionResolver`.
+You can resolve the version through one of the built-in options listed below, or
+alternatively use a custom `ApiVersionResolver`:
+
+- Request header
+- Request parameter
+- Path segment
+- Media type parameter
 
 TIP: When using a path segment, consider configuring a shared path prefix externally
 in xref:web/webmvc/mvc-config/path-matching.adoc[Path Matching] options.
 
-Raw version values are parsed with `SemanticVersionParser` by default, but you can use
+By default, the version is parsed with `SemanticVersionParser`, but you can also configure
 a custom xref:web/webmvc-versioning.adoc#mvc-versioning-parser[ApiVersionParser].
 
-"Supported" versions are transparently detected from versions declared in request mappings
-for convenience, but you can turn that off through a flag in the MVC config, and use only
-the versions configured explicitly in the config. Requests with a version that is not
-supported are rejected with `InvalidApiVersionException` resulting in a 400 response.
+Supported versions are transparently detected from versions declared in request mappings
+for convenience, but you can turn that off through a flag in the MVC config, and
+consider only the versions configured explicitly in the config as supported.
+Requests with a version that is not supported are rejected with
+`InvalidApiVersionException` resulting in a 400 response.
+
+You can set an `ApiVersionDeprecationHandler` to send information about deprecated
+versions to clients. The built-in standard handler can set "Deprecation", "Sunset", and
+"Link" headers based on https://datatracker.ietf.org/doc/html/rfc9745[RFC 9745] and
+https://datatracker.ietf.org/doc/html/rfc8594[RFC 8594].
 
 Once API versioning is configured, you can begin to map requests to
 xref:web/webmvc/mvc-controller/ann-requestmapping.adoc#mvc-ann-requestmapping-version[controller methods]

spring-webflux/src/main/java/org/springframework/web/reactive/config/ApiVersionConfigurer.java

@@ -53,12 +53,12 @@ public class ApiVersionConfigurer {
 
 	private @Nullable String defaultVersion;
 
-	private @Nullable ApiVersionDeprecationHandler deprecationHandler;
-
 	private final Set<String> supportedVersions = new LinkedHashSet<>();
 
 	private boolean detectSupportedVersions = true;
 
+	private @Nullable ApiVersionDeprecationHandler deprecationHandler;
+
 
 	/**
 	 * Add a resolver that extracts the API version from a request header.
@@ -145,18 +145,6 @@ public class ApiVersionConfigurer {
 		return this;
 	}
 
-	/**
-	 * Configure a handler to add handling for requests with a deprecated API
-	 * version. Typically, this involves sending hints and information about
-	 * the deprecation in response headers.
-	 * @param handler the handler to use
-	 * @see StandardApiVersionDeprecationHandler
-	 */
-	public ApiVersionConfigurer setDeprecationHandler(ApiVersionDeprecationHandler handler) {
-		this.deprecationHandler = handler;
-		return this;
-	}
-
 	/**
 	 * Add to the list of supported versions to check against before raising
 	 * {@link InvalidApiVersionException} for unknown versions.
@@ -187,6 +175,18 @@ public class ApiVersionConfigurer {
 		return this;
 	}
 
+	/**
+	 * Configure a handler to add handling for requests with a deprecated API
+	 * version. Typically, this involves sending hints and information about
+	 * the deprecation in response headers.
+	 * @param handler the handler to use
+	 * @see StandardApiVersionDeprecationHandler
+	 */
+	public ApiVersionConfigurer setDeprecationHandler(ApiVersionDeprecationHandler handler) {
+		this.deprecationHandler = handler;
+		return this;
+	}
+
 	protected @Nullable ApiVersionStrategy getApiVersionStrategy() {
 		if (this.versionResolvers.isEmpty()) {
 			return null;

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/ApiVersionConfigurer.java

@@ -53,12 +53,12 @@ public class ApiVersionConfigurer {
 
 	private @Nullable String defaultVersion;
 
-	private @Nullable ApiVersionDeprecationHandler deprecationHandler;
-
 	private final Set<String> supportedVersions = new LinkedHashSet<>();
 
 	private boolean detectSupportedVersions = true;
 
+	private @Nullable ApiVersionDeprecationHandler deprecationHandler;
+
 
 	/**
 	 * Add resolver to extract the version from a request header.
@@ -145,18 +145,6 @@ public class ApiVersionConfigurer {
 		return this;
 	}
 
-	/**
-	 * Configure a handler to add handling for requests with a deprecated API
-	 * version. Typically, this involves sending hints and information about
-	 * the deprecation in response headers.
-	 * @param handler the handler to use
-	 * @see StandardApiVersionDeprecationHandler
-	 */
-	public ApiVersionConfigurer setDeprecationHandler(ApiVersionDeprecationHandler handler) {
-		this.deprecationHandler = handler;
-		return this;
-	}
-
 	/**
 	 * Add to the list of supported versions to check against before raising
 	 * {@link InvalidApiVersionException} for unknown versions.
@@ -187,6 +175,18 @@ public class ApiVersionConfigurer {
 		return this;
 	}
 
+	/**
+	 * Configure a handler to add handling for requests with a deprecated API
+	 * version. Typically, this involves sending hints and information about
+	 * the deprecation in response headers.
+	 * @param handler the handler to use
+	 * @see StandardApiVersionDeprecationHandler
+	 */
+	public ApiVersionConfigurer setDeprecationHandler(ApiVersionDeprecationHandler handler) {
+		this.deprecationHandler = handler;
+		return this;
+	}
+
 	protected @Nullable ApiVersionStrategy getApiVersionStrategy() {
 		if (this.versionResolvers.isEmpty()) {
 			return null;