#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);
+	}
+
+}

src/test/java/org/springframework/hateoas/alps/AlpsLinkDiscoverUnitTest.java

@@ -0,0 +1,81 @@
+/*
+ * 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 static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.assertThat;
+
+import java.io.IOException;
+import java.nio.charset.Charset;
+
+import org.junit.Test;
+
+import org.springframework.core.io.DefaultResourceLoader;
+import org.springframework.core.io.ResourceLoader;
+import org.springframework.hateoas.Link;
+import org.springframework.hateoas.LinkDiscoverer;
+import org.springframework.hateoas.core.AbstractLinkDiscovererUnitTest;
+import org.springframework.util.StreamUtils;
+
+/**
+ * @author Greg Turnquist
+ */
+public class AlpsLinkDiscoverUnitTest extends AbstractLinkDiscovererUnitTest {
+
+	LinkDiscoverer discoverer = new AlpsLinkDiscoverer();
+
+	ResourceLoader loader = new DefaultResourceLoader();
+
+	@Test
+	public void discoversFullyQualifiedRel() {
+
+		Link link = getDiscoverer().findLinkWithRel("http://foo.com/bar", getInputString());
+
+		assertThat(link, is(notNullValue()));
+		assertThat(link.getHref(), is("fullRelHref"));
+	}
+
+	/**
+	 * Return the {@link LinkDiscoverer} to be tested.
+	 *
+	 * @return
+	 */
+	@Override
+	protected LinkDiscoverer getDiscoverer() {
+		return discoverer;
+	}
+
+	/**
+	 * Return the JSON structure we expect to find the links in.
+	 *
+	 * @return
+	 */
+	@Override
+	protected String getInputString() {
+		try {
+			return StreamUtils.copyToString(
+				loader.getResource("classpath:org/springframework/hateoas/alps/link-discoverer.json").getInputStream(),
+				Charset.defaultCharset());
+		} catch (IOException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+	@Override
+	protected String getInputStringWithoutLinkContainer() {
+		return "{}";
+	}
+}

src/test/java/org/springframework/hateoas/hal/HalLinkDiscovererUnitTest.java

@@ -19,6 +19,8 @@ import static org.hamcrest.CoreMatchers.*;
 import static org.junit.Assert.*;
 
 import org.junit.Test;
+
+import org.springframework.hateoas.Link;
 import org.springframework.hateoas.LinkDiscoverer;
 import org.springframework.hateoas.MediaTypes;
 import org.springframework.hateoas.core.AbstractLinkDiscovererUnitTest;
@@ -40,7 +42,11 @@ public class HalLinkDiscovererUnitTest extends AbstractLinkDiscovererUnitTest {
 	 */
 	@Test
 	public void discoversFullyQualifiedRel() {
-		assertThat(getDiscoverer().findLinkWithRel("http://foo.com/bar", SAMPLE), is(notNullValue()));
+
+		Link link = getDiscoverer().findLinkWithRel("http://foo.com/bar", SAMPLE);
+
+		assertThat(link, is(notNullValue()));
+		assertThat(link.getHref(), is("fullRelHref"));
 	}
 
 	/**

src/test/resources/org/springframework/hateoas/alps/link-discoverer.json

@@ -0,0 +1,23 @@
+{
+  "version" : "1.0",
+  "doc" : {
+    "href" : "http://example.org/samples/full/doc.html"
+  },
+  "descriptors" : [ {
+    "id" : "sfirst descriptor",
+    "name" : "relation",
+    "href" : "firstHref"
+  }, {
+    "id" : "second description",
+    "name" : "relation",
+    "href" : "secondHref"
+  }, {
+    "id" : "self descriptor",
+    "name" : "self",
+    "href" : "selfHref"
+  }, {
+    "id" : "fully qualified descriptor",
+    "name" : "http://foo.com/bar",
+    "href" : "fullRelHref"
+  } ]
+}