#1060 - Properly handle an empty list of hypermedia types for EnableHypermediaSupport.

Author: gregturn

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

@@ -44,7 +44,7 @@ public String[] selectImports(AnnotationMetadata metadata) {
 
 		Map<String, Object> attributes = metadata.getAnnotationAttributes(EnableHypermediaSupport.class.getName());
 
-		List<MediaType> types = attributes == null //
+		List<MediaType> mediaTypes = attributes == null //
 				? Collections.emptyList() //
 				: Arrays.stream((HypermediaType[]) attributes.get("type")) //
 						.flatMap(it -> it.getMediaTypes().stream()) //
@@ -53,10 +53,18 @@ public String[] selectImports(AnnotationMetadata metadata) {
 		List<MediaTypeConfigurationProvider> configurationProviders = SpringFactoriesLoader.loadFactories(
 				MediaTypeConfigurationProvider.class, HypermediaConfigurationImportSelector.class.getClassLoader());
 
-		// Filter the ones supporting the given media types
 		return configurationProviders.stream() //
-				.filter(it -> it.supportsAny(types)) //
-				.map(MediaTypeConfigurationProvider::getConfiguration) //
+				.filter(it -> {
+					// If there are no types, then let them all through
+					if (mediaTypes.isEmpty()) {
+						return true;
+					}
+					// Filter the ones supporting the given media types
+					return it.supportsAny(mediaTypes);
+				}) //
+				.map((MediaTypeConfigurationProvider mediaTypeConfigurationProvider) -> {
+					return mediaTypeConfigurationProvider.getConfiguration();
+				}) //
 				.map(Class::getName) //
 				.toArray(String[]::new);
 	}

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

@@ -89,6 +89,22 @@ void testAllImportConfigurations() {
 		});
 	}
 
+	@Test // #1060
+	void testEmptyHypermediaTypes() {
+
+		withContext(NoConfig.class, context -> {
+
+			Map<String, LinkDiscoverer> linkDiscoverers = context.getBeansOfType(LinkDiscoverer.class);
+
+			assertThat(linkDiscoverers.values()).extracting("class") //
+				.containsExactlyInAnyOrder( //
+					HalLinkDiscoverer.class, //
+					HalFormsLinkDiscoverer.class, //
+					UberLinkDiscoverer.class, //
+					CollectionJsonLinkDiscoverer.class);
+		});
+	}
+
 	@EnableHypermediaSupport(type = HAL)
 	static class HalConfig {
 
@@ -108,4 +124,9 @@ static class HalAndHalFormsConfig {
 	static class AllConfig {
 
 	}
+
+	@EnableHypermediaSupport(type = { })
+	static class NoConfig {
+
+	}
 }

src/test/java/org/springframework/hateoas/support/CustomHypermediaConfigurationProvider.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2019 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.support;
+
+import java.util.Collection;
+
+import org.springframework.hateoas.config.HypermediaMappingInformation;
+import org.springframework.hateoas.config.MediaTypeConfigurationProvider;
+import org.springframework.http.MediaType;
+
+/**
+ * @author Greg Turnquist
+ */
+public class CustomHypermediaConfigurationProvider implements MediaTypeConfigurationProvider {
+
+	@Override
+	public Class<? extends HypermediaMappingInformation> getConfiguration() {
+		return CustomHypermediaType.class;
+	}
+
+	@Override
+	public boolean supportsAny(Collection<MediaType> mediaTypes) {
+		return mediaTypes.stream().anyMatch(mediaType -> mediaType.isCompatibleWith(CustomHypermediaType.FRODO_MEDIATYPE));
+	}
+}

src/test/resources/META-INF/spring.factories

@@ -0,0 +1,2 @@
+org.springframework.hateoas.config.MediaTypeConfigurationProvider=\
+ org.springframework.hateoas.support.CustomHypermediaConfigurationProvider