#1591 - Support for custom media type aliases in HAL FORMS.

src/main/java/org/springframework/hateoas/mediatype/hal/forms/HalFormsConfiguration.java

@@ -15,7 +15,10 @@
  */
 package org.springframework.hateoas.mediatype.hal.forms;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.function.Consumer;
@@ -23,7 +26,9 @@ import java.util.function.Function;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.hateoas.AffordanceModel.PropertyMetadata;
+import org.springframework.hateoas.MediaTypes;
 import org.springframework.hateoas.mediatype.hal.HalConfiguration;
+import org.springframework.http.MediaType;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -41,6 +46,7 @@ public class HalFormsConfiguration {
 	private final Map<Class<?>, String> patterns;
 	private final Consumer<ObjectMapper> objectMapperCustomizer;
 	private final HalFormsOptionsFactory options;
+	private final List<MediaType> mediaTypes;
 
 	/**
 	 * Creates a new {@link HalFormsConfiguration} backed by a default {@link HalConfiguration}.
@@ -55,21 +61,25 @@ public class HalFormsConfiguration {
 	 * @param halConfiguration must not be {@literal null}.
 	 */
 	public HalFormsConfiguration(HalConfiguration halConfiguration) {
-		this(halConfiguration, new HashMap<>(), new HalFormsOptionsFactory(), __ -> {});
+		this(halConfiguration, new HashMap<>(), new HalFormsOptionsFactory(), __ -> {},
+				Collections.singletonList(MediaTypes.HAL_FORMS_JSON));
 	}
 
 	private HalFormsConfiguration(HalConfiguration halConfiguration, Map<Class<?>, String> patterns,
-			HalFormsOptionsFactory options, @Nullable Consumer<ObjectMapper> objectMapperCustomizer) {
+			HalFormsOptionsFactory options, @Nullable Consumer<ObjectMapper> objectMapperCustomizer,
+			List<MediaType> mediaTypes) {
 
 		Assert.notNull(halConfiguration, "HalConfiguration must not be null!");
 		Assert.notNull(patterns, "Patterns must not be null!");
 		Assert.notNull(objectMapperCustomizer, "ObjectMapper customizer must not be null!");
 		Assert.notNull(options, "HalFormsSuggests must not be null!");
+		Assert.notNull(mediaTypes, "Media types must not be null!");
 
 		this.halConfiguration = halConfiguration;
 		this.patterns = patterns;
 		this.objectMapperCustomizer = objectMapperCustomizer;
 		this.options = options;
+		this.mediaTypes = new ArrayList<>(mediaTypes);
 	}
 
 	/**
@@ -106,7 +116,7 @@ public class HalFormsConfiguration {
 		Map<Class<?>, String> newPatterns = new HashMap<>(patterns);
 		newPatterns.put(type, pattern);
 
-		return new HalFormsConfiguration(halConfiguration, newPatterns, options, objectMapperCustomizer);
+		return new HalFormsConfiguration(halConfiguration, newPatterns, options, objectMapperCustomizer, mediaTypes);
 	}
 
 	/**
@@ -122,7 +132,30 @@ public class HalFormsConfiguration {
 
 		return this.objectMapperCustomizer == objectMapperCustomizer //
 				? this //
-				: new HalFormsConfiguration(halConfiguration, patterns, options, objectMapperCustomizer);
+				: new HalFormsConfiguration(halConfiguration, patterns, options, objectMapperCustomizer, mediaTypes);
+	}
+
+	/**
+	 * Registers additional media types that are supposed to be aliases to {@link MediaTypes#HAL_FORMS_JSON}. Registered
+	 * {@link MediaType}s will be preferred over the default one, i.e. they'll be listed first in client's accept headers
+	 * etc.
+	 *
+	 * @param mediaType must not be {@literal null}.
+	 * @return will never be {@literal null}.
+	 * @since 1.4
+	 */
+	public HalFormsConfiguration withMediaType(MediaType mediaType) {
+
+		Assert.notNull(mediaType, "MediaType must not be null!");
+
+		if (mediaTypes.contains(mediaType)) {
+			return this;
+		}
+
+		List<MediaType> newMediaTypes = new ArrayList<>(mediaTypes);
+		newMediaTypes.add(mediaTypes.size() - 1, mediaType);
+
+		return new HalFormsConfiguration(halConfiguration, patterns, options, objectMapperCustomizer, newMediaTypes);
 	}
 
 	/**
@@ -154,7 +187,7 @@ public class HalFormsConfiguration {
 			Function<PropertyMetadata, HalFormsOptions> creator) {
 
 		return new HalFormsConfiguration(halConfiguration, patterns, options.withOptions(type, property, creator),
-				objectMapperCustomizer);
+				objectMapperCustomizer, mediaTypes);
 	}
 
 	/**
@@ -179,9 +212,18 @@ public class HalFormsConfiguration {
 	 * Returns the regular expression pattern that is registered for the given type.
 	 *
 	 * @param type must not be {@literal null}.
-	 * @return
+	 * @return will never be {@literal null}.
 	 */
 	Optional<String> getTypePatternFor(ResolvableType type) {
 		return Optional.ofNullable(patterns.get(type.resolve(Object.class)));
 	}
+
+	/**
+	 * The {@link MediaType}s that we want to register this configuration for.
+	 *
+	 * @return will never be {@literal null}.
+	 */
+	List<MediaType> getMediaTypes() {
+		return Collections.unmodifiableList(mediaTypes);
+	}
 }

src/main/java/org/springframework/hateoas/mediatype/hal/forms/HalFormsMediaTypeConfiguration.java

@@ -23,7 +23,6 @@ import org.springframework.beans.factory.support.AbstractAutowireCapableBeanFact
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.hateoas.client.LinkDiscoverer;
-import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType;
 import org.springframework.hateoas.config.HypermediaMappingInformation;
 import org.springframework.hateoas.mediatype.MessageResolver;
 import org.springframework.hateoas.mediatype.hal.CurieProvider;
@@ -106,7 +105,7 @@ class HalFormsMediaTypeConfiguration implements HypermediaMappingInformation {
 	 */
 	@Override
 	public List<MediaType> getMediaTypes() {
-		return HypermediaType.HAL_FORMS.getMediaTypes();
+		return getResolvedConfiguration().getMediaTypes();
 	}
 
 	HalFormsConfiguration getResolvedConfiguration() {

src/test/java/org/springframework/hateoas/mediatype/hal/forms/HalFormsMediaTypeConfigurationIntegrationTest.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.hateoas.mediatype.hal.forms;
+
+import static org.assertj.core.api.Assertions.*;
+import static org.springframework.hateoas.support.ContextTester.*;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.hateoas.config.EnableHypermediaSupport;
+import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType;
+import org.springframework.hateoas.mediatype.MediaTypeTestUtils;
+import org.springframework.http.MediaType;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+
+/**
+ * Integration tests for HAL media type configuration.
+ *
+ * @author Oliver Drotbohm
+ */
+class HalFormsMediaTypeConfigurationIntegrationTest {
+
+	static final MediaType CUSTOM_MEDIA_TYPE = MediaType.parseMediaType("application/vnd.my-custom-mediatype");
+
+	@Test // #1591
+	void includesCustomMediaTypeFromConfiguration() {
+
+		withServletContext(ConfigurationWithCustomMediaType.class, it -> {
+			assertThat(MediaTypeTestUtils.getSupportedHypermediaTypes(it)).contains(CUSTOM_MEDIA_TYPE);
+		});
+	}
+
+	@Configuration
+	@EnableWebMvc
+	@EnableHypermediaSupport(type = HypermediaType.HAL_FORMS)
+	static class ConfigurationWithCustomMediaType {
+
+		@Bean
+		HalFormsConfiguration halConfiguration() {
+			return new HalFormsConfiguration().withMediaType(CUSTOM_MEDIA_TYPE);
+		}
+	}
+}