#597 - Add ALPS media type and LinkDiscoverer.

Migrate general ALPS material from Spring Data REST into Spring HATEOAS.

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

@@ -23,6 +23,7 @@ import org.springframework.http.MediaType;
  * @author Oliver Gierke
  * @author Przemek Nowak
  * @author Drummond Dawson
+ * @author Greg Turnquist
  */
 public class MediaTypes {
 
@@ -45,4 +46,14 @@ public class MediaTypes {
 	 * 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);
+
+	/**
+	 * A string equivalient of {@link MediaTypes#ALPS_JSON}.
+	 */
+	public static final String ALPS_JSON_VALUE = "application/alps+json";
+
+	/**
+	 * Public constant media type for {@code application/alps+json}.
+	 */
+	public static final MediaType ALPS_JSON = MediaType.parseMediaType(ALPS_JSON_VALUE);
 }

src/main/java/org/springframework/hateoas/alps/AlpsLinkDiscoverer.java

@@ -0,0 +1,33 @@
+/*
+ * 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.alps;
+
+import org.springframework.hateoas.LinkDiscoverer;
+import org.springframework.hateoas.MediaTypes;
+import org.springframework.hateoas.core.JsonPathLinkDiscoverer;
+
+/**
+ * {@link LinkDiscoverer} implementation to find ALPS-based links.
+ * 
+ * @author Greg Turnquist
+ */
+public class AlpsLinkDiscoverer extends JsonPathLinkDiscoverer {
+
+	public AlpsLinkDiscoverer() {
+		super("$.descriptors[?(@.name == '%s')].href", MediaTypes.ALPS_JSON);
+	}
+
+}