GH-2276 - Add support for official IANA HAL media type identifier.

The media type identifier for HAL registered with the IANA is application/vnd.hal+json, notably different from application/hal+json used in the RFC document. This commit adds a constant for that media type identifier and updates the configuration spots necessary to additionally consider it.

[0] https://www.iana.org/assignments/media-types/application/vnd.hal+json
[1] https://datatracker.ietf.org/doc/html/draft-kelly-json-hal

Author: odrotbohm

src/main/java/org/springframework/hateoas/MediaTypes.java

@@ -19,7 +19,7 @@
 
 /**
  * Constants for well-known hypermedia types.
- * 
+ *
  * @author Oliver Gierke
  * @author Przemek Nowak
  * @author Drummond Dawson
@@ -37,6 +37,20 @@ public class MediaTypes {
 	 */
 	public static final MediaType HAL_JSON = MediaType.valueOf(HAL_JSON_VALUE);
 
+	/**
+	 * A String equivalent of {@link MediaTypes#VND_HAL_JSON}.
+	 *
+	 * @since 2.5
+	 */
+	public static final String VND_HAL_JSON_VALUE = "application/vnd.hal+json";
+
+	/**
+	 * Public constant media type for {@code application/vnd.hal+json}.
+	 *
+	 * @since 2.5
+	 */
+	public static final MediaType VND_HAL_JSON = MediaType.valueOf(VND_HAL_JSON_VALUE);
+
 	/**
 	 * A String equivalent of {@link MediaTypes#ALPS_JSON}.
 	 */
@@ -76,7 +90,7 @@ public class MediaTypes {
 	 * Public constant media type for {@code application/vnd.amundsen-uber+json}.
 	 */
 	public static final MediaType UBER_JSON = MediaType.parseMediaType(UBER_JSON_VALUE);
-	
+
 	/**
 	 * A String equivalent of {@link MediaTypes#VND_ERROR_JSON}.
 	 */

src/main/java/org/springframework/hateoas/config/EnableHypermediaSupport.java

@@ -20,13 +20,12 @@
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
+import java.util.List;
 
-import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Import;
 import org.springframework.hateoas.MediaTypes;
 import org.springframework.hateoas.support.WebStack;
 import org.springframework.http.MediaType;
-import org.springframework.web.reactive.function.client.WebClient;
 
 /**
  * Activates hypermedia support in the {@link ApplicationContext}. Will register infrastructure beans to support all
@@ -50,8 +49,8 @@
 
 	/**
 	 * Configures which {@link WebStack}s we're supposed to enable support for. By default we're activating it for all
-	 * available ones if they happen to be in use. Configure this explicitly in case you're using WebFlux components
-	 * like {@link WebClient} but don't want to use hypermedia operations with it.
+	 * available ones if they happen to be in use. Configure this explicitly in case you're using WebFlux components like
+	 * {@link WebClient} but don't want to use hypermedia operations with it.
 	 *
 	 * @return
 	 */
@@ -69,9 +68,9 @@ enum HypermediaType {
 		 * HAL - Hypermedia Application Language.
 		 *
 		 * @see http://stateless.co/hal_specification.html
-		 * @see https://tools.ietf.org/html/draft-kelly-json-hal-05
+		 * @see https://tools.ietf.org/html/draft-kelly-json-hal
 		 */
-		HAL(MediaTypes.HAL_JSON, "hal"),
+		HAL(List.of(MediaTypes.HAL_JSON, MediaTypes.VND_HAL_JSON), "hal"),
 
 		/**
 		 * HAL-FORMS - Independent, backward-compatible extension of the HAL designed to add runtime FORM support
@@ -96,18 +95,33 @@ enum HypermediaType {
 		 */
 		UBER(MediaTypes.UBER_JSON, "uber");
 
-		private final MediaType mediaTypes;
+		private final List<MediaType> mediaTypes;
 		private final String localPackageName;
 
 		HypermediaType(MediaType mediaType, String localPackageName) {
-			this.mediaTypes = mediaType;
+			this.mediaTypes = List.of(mediaType);
 			this.localPackageName = localPackageName;
 		}
 
-		public MediaType getMediaType() {
+		HypermediaType(List<MediaType> mediaTypes, String localPackageName) {
+			this.mediaTypes = mediaTypes;
+			this.localPackageName = localPackageName;
+		}
+
+		public List<MediaType> getMediaTypes() {
 			return this.mediaTypes;
 		}
 
+		/**
+		 * @deprecated since 2.5, in favor of {@link #getMediaTypes()} as a logical media type might have been associated
+		 *             with multiple media type identifiers (see {@link #HAL}).
+		 * @return will never be {@literal null}.
+		 */
+		@Deprecated(since = "2.5", forRemoval = true)
+		public MediaType getMediaType() {
+			return this.mediaTypes.get(0);
+		}
+
 		public String getLocalPackageName() {
 			return localPackageName;
 		}

src/main/java/org/springframework/hateoas/config/HypermediaConfigurationImportSelector.java

@@ -79,7 +79,7 @@ public String[] selectImports(AnnotationMetadata metadata) {
 		List<MediaType> types = attributes == null //
 				? Collections.emptyList() //
 				: Arrays.stream((HypermediaType[]) attributes.get("type")) //
-						.map(it -> it.getMediaType()) //
+						.flatMap(it -> it.getMediaTypes().stream()) //
 						.collect(Collectors.toList());
 
 		if (!beanFactory.containsBean("hateoasMediaTypeConfigurer")) {

src/main/java/org/springframework/hateoas/mediatype/collectionjson/CollectionJsonMediaTypeConfiguration.java

@@ -15,7 +15,6 @@
  */
 package org.springframework.hateoas.mediatype.collectionjson;
 
-import java.util.Collections;
 import java.util.List;
 
 import org.springframework.context.annotation.Bean;
@@ -48,7 +47,7 @@ LinkDiscoverer collectionJsonLinkDiscoverer() {
 	 */
 	@Override
 	public List<MediaType> getMediaTypes() {
-		return Collections.singletonList(HypermediaType.COLLECTION_JSON.getMediaType());
+		return HypermediaType.COLLECTION_JSON.getMediaTypes();
 	}
 
 	/*

src/main/java/org/springframework/hateoas/mediatype/hal/HalConfiguration.java

@@ -16,14 +16,12 @@
 package org.springframework.hateoas.mediatype.hal;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.function.Consumer;
 
-import org.springframework.hateoas.Link;
 import org.springframework.hateoas.LinkRelation;
 import org.springframework.hateoas.MediaTypes;
 import org.springframework.http.MediaType;
@@ -70,7 +68,7 @@ public class HalConfiguration {
 	public HalConfiguration() {
 
 		this(RenderSingleLinks.AS_SINGLE, new LinkedHashMap<>(), true, true, __ -> {},
-				Collections.singletonList(MediaTypes.HAL_JSON));
+				List.of(MediaTypes.HAL_JSON, MediaTypes.VND_HAL_JSON));
 	}
 
 	private HalConfiguration(RenderSingleLinks renderSingleLinks, Map<String, RenderSingleLinks> singleLinksPerPattern,

src/main/java/org/springframework/hateoas/mediatype/hal/HalLinkDiscoverer.java

@@ -21,7 +21,6 @@
 import org.springframework.hateoas.LinkRelation;
 import org.springframework.hateoas.MediaTypes;
 import org.springframework.hateoas.client.JsonPathLinkDiscoverer;
-import org.springframework.hateoas.client.LinkDiscoverer;
 import org.springframework.http.MediaType;
 
 /**
@@ -36,7 +35,7 @@ public class HalLinkDiscoverer extends JsonPathLinkDiscoverer {
 	 * Constructor for {@link MediaTypes#HAL_JSON}.
 	 */
 	public HalLinkDiscoverer() {
-		this(MediaTypes.HAL_JSON);
+		this(MediaTypes.HAL_JSON, MediaTypes.VND_HAL_JSON);
 	}
 
 	protected HalLinkDiscoverer(MediaType... mediaTypes) {

src/main/java/org/springframework/hateoas/mediatype/hal/HalMediaTypeConfigurationProvider.java

@@ -44,6 +44,8 @@ public Class<? extends HypermediaMappingInformation> getConfiguration() {
 	 */
 	@Override
 	public boolean supportsAny(Collection<MediaType> mediaTypes) {
-		return mediaTypes.contains(MediaTypes.HAL_JSON);
+
+		return mediaTypes.contains(MediaTypes.HAL_JSON)
+				|| mediaTypes.contains(MediaTypes.VND_HAL_JSON);
 	}
 }

src/main/java/org/springframework/hateoas/mediatype/hal/HalTraversonDefaults.java

@@ -40,7 +40,8 @@
  */
 class HalTraversonDefaults implements TraversonDefaults {
 
-	private static final List<MediaType> HAL_FLAVORS = Collections.singletonList(MediaTypes.HAL_JSON);
+	private static final List<MediaType> HAL_FLAVORS = List.of(MediaTypes.HAL_JSON, MediaTypes.VND_HAL_JSON,
+			MediaTypes.HAL_FORMS_JSON);
 
 	/*
 	 * (non-Javadoc)
@@ -70,8 +71,8 @@ public List<HttpMessageConverter<?>> getHttpMessageConverters(Collection<MediaTy
 	@Override
 	public List<LinkDiscoverer> getLinkDiscoverers(Collection<MediaType> mediaTypes) {
 
-		return mediaTypes.stream().anyMatch(it -> it.isCompatibleWith(MediaTypes.HAL_JSON)) //
-				? Collections.singletonList(new HalLinkDiscoverer()) //
+		return mediaTypes.stream().anyMatch(it -> HAL_FLAVORS.stream().anyMatch(it::isCompatibleWith)) //
+				? List.of(new HalLinkDiscoverer()) //
 				: Collections.emptyList();
 	}
 

src/main/java/org/springframework/hateoas/mediatype/uber/UberMediaTypeConfiguration.java

@@ -15,7 +15,6 @@
  */
 package org.springframework.hateoas.mediatype.uber;
 
-import java.util.Collections;
 import java.util.List;
 
 import org.springframework.context.annotation.Bean;
@@ -48,7 +47,7 @@ LinkDiscoverer uberLinkDiscoverer() {
 	 */
 	@Override
 	public List<MediaType> getMediaTypes() {
-		return Collections.singletonList(HypermediaType.UBER.getMediaType());
+		return HypermediaType.UBER.getMediaTypes();
 	}
 
 	/*

src/test/java/org/springframework/hateoas/config/EnableHypermediaSupportIntegrationTest.java

@@ -110,6 +110,8 @@ void registersHalLinkDiscoverers() {
 			assertThat(discoverers).isNotNull();
 			assertThat(discoverers.getLinkDiscovererFor(MediaTypes.HAL_JSON))
 					.hasValueSatisfying(HalLinkDiscoverer.class::isInstance);
+			assertThat(discoverers.getLinkDiscovererFor(MediaTypes.VND_HAL_JSON))
+					.hasValueSatisfying(HalLinkDiscoverer.class::isInstance);
 			assertRelProvidersSetUp(context);
 		});
 	}
@@ -138,6 +140,8 @@ void registersHalAndHalFormsLinkDiscoverers() {
 			assertThat(discoverers).isNotNull();
 			assertThat(discoverers.getLinkDiscovererFor(MediaTypes.HAL_JSON))
 					.hasValueSatisfying(HalLinkDiscoverer.class::isInstance);
+			assertThat(discoverers.getLinkDiscovererFor(MediaTypes.VND_HAL_JSON))
+					.hasValueSatisfying(HalLinkDiscoverer.class::isInstance);
 
 			assertThat(discoverers.getLinkDiscovererFor(MediaTypes.HAL_FORMS_JSON))
 					.hasValueSatisfying(HalFormsLinkDiscoverer.class::isInstance);