#288 - Opt to render single links as an array.

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

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2017 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
+ *
+ *      http://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;
+
+/**
+ * @author Greg Turnquist
+ */
+public interface HypermediaConfiguration {
+
+}

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

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2017 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
+ *
+ *      http://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;
+
+/**
+ * Whether to render a single {@link Link} as either a single entry or a collection.
+ */
+public enum RenderSingleLinks {
+
+	/**
+	 * A single {@link Link} is rendered as a JSON object.
+	 */
+	AS_SINGLE,
+
+	/**
+	 * A single {@link Link} is rendered as a JSON Array.
+	 */
+	AS_ARRAY
+}

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

@@ -25,6 +25,7 @@
 import org.springframework.context.annotation.Import;
 import org.springframework.hateoas.EntityLinks;
 import org.springframework.hateoas.LinkDiscoverer;
+import org.springframework.hateoas.RenderSingleLinks;
 
 /**
  * Activates hypermedia support in the {@link ApplicationContext}. Will register infrastructure beans available for
@@ -58,7 +59,7 @@
 	 * 
 	 * @author Oliver Gierke
 	 */
-	static enum HypermediaType {
+	enum HypermediaType {
 
 		/**
 		 * HAL - Hypermedia Application Language.

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

@@ -46,13 +46,15 @@
 import org.springframework.hateoas.LinkDiscoverer;
 import org.springframework.hateoas.LinkDiscoverers;
 import org.springframework.hateoas.RelProvider;
+import org.springframework.hateoas.RenderSingleLinks;
 import org.springframework.hateoas.ResourceSupport;
 import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType;
 import org.springframework.hateoas.core.AnnotationRelProvider;
 import org.springframework.hateoas.core.DefaultRelProvider;
 import org.springframework.hateoas.core.DelegatingRelProvider;
 import org.springframework.hateoas.core.EvoInflectorRelProvider;
 import org.springframework.hateoas.hal.CurieProvider;
+import org.springframework.hateoas.hal.HalConfiguration;
 import org.springframework.hateoas.hal.HalLinkDiscoverer;
 import org.springframework.hateoas.hal.Jackson2HalModule;
 import org.springframework.hateoas.mvc.TypeConstrainedMappingJackson2HttpMessageConverter;
@@ -76,7 +78,7 @@
  * 
  * @author Oliver Gierke
  */
-class HypermediaSupportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
+class HypermediaSupportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar, BeanFactoryAware {
 
 	private static final String DELEGATING_REL_PROVIDER_BEAN_NAME = "_relProvider";
 	private static final String LINK_DISCOVERER_REGISTRY_BEAN_NAME = "_linkDiscovererRegistry";
@@ -89,8 +91,10 @@ class HypermediaSupportBeanDefinitionRegistrar implements ImportBeanDefinitionRe
 	private static final boolean EVO_PRESENT = ClassUtils.isPresent("org.atteo.evo.inflector.English", null);
 
 	private final ImportBeanDefinitionRegistrar linkBuilderBeanDefinitionRegistrar = new LinkBuilderBeanDefinitionRegistrar();
+
+	private BeanFactory beanFactory;
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.context.annotation.ImportBeanDefinitionRegistrar#registerBeanDefinitions(org.springframework.core.type.AnnotationMetadata, org.springframework.beans.factory.support.BeanDefinitionRegistry)
 	 */
@@ -125,6 +129,16 @@ public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionR
 				BeanDefinitionBuilder builder = rootBeanDefinition(Jackson2ModuleRegisteringBeanPostProcessor.class);
 				registerSourcedBeanDefinition(builder, metadata, registry);
 			}
+
+			try {
+				this.beanFactory.getBean(HalConfiguration.class);
+			} catch (BeansException e) {
+
+				// If no HalConfiguration bean, create a default one.
+				BeanDefinitionBuilder defaultHalConfiguration = rootBeanDefinition(HalConfiguration.class);
+				defaultHalConfiguration.addPropertyValue("renderSingleLinks", RenderSingleLinks.AS_SINGLE);
+				registerSourcedBeanDefinition(defaultHalConfiguration, metadata, registry);
+			}
 		}
 
 		if (!types.isEmpty()) {
@@ -143,6 +157,11 @@ public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionR
 		registerRelProviderPluginRegistryAndDelegate(registry);
 	}
 
+	@Override
+	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
+		this.beanFactory = beanFactory;
+	}
+
 	/**
 	 * Registers bean definitions for a {@link PluginRegistry} to capture {@link RelProvider} instances. Wraps the
 	 * registry into a {@link DelegatingRelProvider} bean definition backed by the registry.

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

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2017 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
+ *
+ *      http://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.hal;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+import lombok.experimental.Wither;
+
+import org.springframework.hateoas.HypermediaConfiguration;
+import org.springframework.hateoas.RenderSingleLinks;
+
+/**
+ * @author Greg Turnquist
+ */
+@AllArgsConstructor
+@NoArgsConstructor
+public class HalConfiguration implements HypermediaConfiguration {
+
+	private @Wither @Getter @Setter RenderSingleLinks renderSingleLinks;
+}