#470 - Added HAL JSON UTF-8 variant to MediaTypes.

Added application/hal+json;charset=UTF-8 to the media types enum. Traverson now configures all HAL flavors to be supported by the registered HAL-specific HttpMessageConverter.

Removed nullability of media type in JsonPathLinkDiscoverer. This requires subclasses that want to support all media types to explicitly configure MediaType.ALL.

Heavily inspired by the PR submitted by @drummond but very significantly rewritten.

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

@@ -22,6 +22,7 @@ import org.springframework.http.MediaType;
  * 
  * @author Oliver Gierke
  * @author Przemek Nowak
+ * @author Drummond Dawson
  */
 public class MediaTypes {
 
@@ -34,4 +35,14 @@ public class MediaTypes {
 	 * Public constant media type for {@code application/hal+json}.
 	 */
 	public static final MediaType HAL_JSON = MediaType.valueOf(HAL_JSON_VALUE);
+
+	/**
+	 * A String equivalent of {@link MediaTypes#HAL_JSON_UTF8}.
+	 */
+	public static final String HAL_JSON_UTF8_VALUE = HAL_JSON_VALUE + ";charset=UTF-8";
+
+	/**
+	 * Public constant media type for {@code application/hal+json;charset=UTF-8}.
+	 */
+	public static final MediaType HAL_JSON_UTF8 = MediaType.valueOf(HAL_JSON_UTF8_VALUE);
 }

src/main/java/org/springframework/hateoas/client/Traverson.java

@@ -21,6 +21,7 @@ import java.net.URI;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
@@ -130,13 +131,34 @@ public class Traverson {
 		List<HttpMessageConverter<?>> converters = new ArrayList<HttpMessageConverter<?>>();
 		converters.add(new StringHttpMessageConverter(Charset.forName("UTF-8")));
 
-		if (mediaTypes.contains(MediaTypes.HAL_JSON)) {
-			converters.add(getHalConverter());
+		List<MediaType> halFlavors = getHalJsonFlavors(mediaTypes);
+
+		if (!halFlavors.isEmpty()) {
+			converters.add(getHalConverter(halFlavors));
 		}
 
 		return converters;
 	}
 
+	/**
+	 * Returns all HAL JSON compatible media types from the given list.
+	 * 
+	 * @param mediaTypes must not be {@literal null}.
+	 * @return
+	 */
+	private static List<MediaType> getHalJsonFlavors(Collection<MediaType> mediaTypes) {
+
+		List<MediaType> result = new ArrayList<MediaType>();
+
+		for (MediaType mediaType : mediaTypes) {
+			if (MediaTypes.HAL_JSON.isCompatibleWith(mediaType)) {
+				result.add(mediaType);
+			}
+		}
+
+		return result;
+	}
+
 	private static final RestOperations createDefaultTemplate(List<MediaType> mediaTypes) {
 
 		RestTemplate template = new RestTemplate();
@@ -150,7 +172,7 @@ public class Traverson {
 	 * 
 	 * @return
 	 */
-	private static final HttpMessageConverter<?> getHalConverter() {
+	private static final HttpMessageConverter<?> getHalConverter(List<MediaType> halFlavours) {
 
 		ObjectMapper mapper = new ObjectMapper();
 		mapper.registerModule(new Jackson2HalModule());
@@ -159,7 +181,7 @@ public class Traverson {
 		MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
 
 		converter.setObjectMapper(mapper);
-		converter.setSupportedMediaTypes(Arrays.asList(MediaTypes.HAL_JSON));
+		converter.setSupportedMediaTypes(halFlavours);
 
 		return converter;
 	}

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

@@ -293,7 +293,7 @@ class HypermediaSupportBeanDefinitionRegistrar implements ImportBeanDefinitionRe
 
 			MappingJackson2HttpMessageConverter halConverter = new TypeConstrainedMappingJackson2HttpMessageConverter(
 					ResourceSupport.class);
-			halConverter.setSupportedMediaTypes(Arrays.asList(HAL_JSON));
+			halConverter.setSupportedMediaTypes(Arrays.asList(HAL_JSON, HAL_JSON_UTF8));
 			halConverter.setObjectMapper(halObjectMapper);
 
 			List<HttpMessageConverter<?>> result = new ArrayList<HttpMessageConverter<?>>(converters.size());

src/main/java/org/springframework/hateoas/core/JsonPathLinkDiscoverer.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.hateoas.core;
 
+import net.minidev.json.JSONArray;
+
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.reflect.Array;
@@ -24,10 +26,9 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
-import net.minidev.json.JSONArray;
-
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.LinkDiscoverer;
+import org.springframework.hateoas.MediaTypes;
 import org.springframework.http.MediaType;
 import org.springframework.util.Assert;
 import org.springframework.util.ReflectionUtils;
@@ -67,23 +68,31 @@ public class JsonPathLinkDiscoverer implements LinkDiscoverer {
 	}
 
 	private final String pathTemplate;
-	private final MediaType mediaType;
+	private final List<MediaType> mediaTypes;
 
 	/**
 	 * Creates a new {@link JsonPathLinkDiscoverer} using the given path template supporting the given {@link MediaType}.
 	 * The template has to contain a single {@code %s} placeholder which will be replaced by the relation type.
 	 * 
 	 * @param pathTemplate must not be {@literal null} or empty and contain a single placeholder.
-	 * @param mediaType the {@link MediaType} to support.
+	 * @param mediaType the primary {@link MediaType}s to support.
+	 * @param additional {@link MediaTypes} to support.
 	 */
-	public JsonPathLinkDiscoverer(String pathTemplate, MediaType mediaType) {
+	public JsonPathLinkDiscoverer(String pathTemplate, MediaType mediaType, MediaType... others) {
 
 		Assert.hasText(pathTemplate, "Path template must not be null!");
 		Assert.isTrue(StringUtils.countOccurrencesOf(pathTemplate, "%s") == 1,
 				"Path template must contain a single placeholder!");
+		Assert.notNull(mediaType, "Primary MediaType must not be null!");
+		Assert.notNull(others, "Other MediaTypes must not be null!");
 
 		this.pathTemplate = pathTemplate;
-		this.mediaType = mediaType;
+
+		List<MediaType> mediaTypes = new ArrayList<MediaType>(others.length + 1);
+		mediaTypes.add(mediaType);
+		mediaTypes.addAll(Arrays.asList(others));
+
+		this.mediaTypes = mediaTypes;
 	}
 
 	/* 
@@ -178,6 +187,13 @@ public class JsonPathLinkDiscoverer implements LinkDiscoverer {
 	 */
 	@Override
 	public boolean supports(MediaType delimiter) {
-		return this.mediaType == null ? true : this.mediaType.isCompatibleWith(delimiter);
+
+		for (MediaType mediaType : this.mediaTypes) {
+			if (mediaType.isCompatibleWith(delimiter)) {
+				return true;
+			}
+		}
+
+		return false;
 	}
 }