Add support for Spring HATEOAS hypermedia in Actuator endpoints

If spring-hateoas is on the classpath and an MvcEndpoint returns a
@ResponseBody it will be extended and wrapped into a Resource with links.
All the existing endpoints that return sensible JSON data can be extended
this way (i.e. not /logfile). The HAL browser will also be added as an
endpoint if available on the classpath. Finally, asciidocs for the
Actuator endpoints are available as a separate jar file, which if
included in an app will also generate a new (HTTP) endpoint.

Fixes gh-1390

spring-boot-samples/spring-boot-sample-hypermedia/src/test/java/demo/HomePageHypermediaApplicationTests.java

@@ -0,0 +1,59 @@
+package demo;
+
+import static org.junit.Assert.assertTrue;
+
+import java.net.URI;
+import java.util.Arrays;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.test.IntegrationTest;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.boot.test.TestRestTemplate;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.MediaType;
+import org.springframework.http.RequestEntity;
+import org.springframework.http.ResponseEntity;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.web.WebAppConfiguration;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = SpringBootHypermediaApplication.class)
+@WebAppConfiguration
+@IntegrationTest("server.port=0")
+public class HomePageHypermediaApplicationTests {
+
+	@Value("${local.server.port}")
+	private int port;
+
+	@Test
+	public void home() {
+		String response = new TestRestTemplate().getForObject("http://localhost:" + port,
+				String.class);
+		assertTrue("Wrong body: " + response, response.contains("\"_links\":"));
+		assertTrue("Wrong body: " + response, response.contains("\"curies\":"));
+	}
+
+	@Test
+	public void homeWithJson() throws Exception {
+		HttpHeaders headers = new HttpHeaders();
+		headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
+		ResponseEntity<String> response = new TestRestTemplate().exchange(
+				new RequestEntity<Void>(headers , HttpMethod.GET, new URI("http://localhost:"
+						+ port + "/")), String.class);
+		assertTrue("Wrong body: " + response, response.getBody().contains("\"_links\":"));
+	}
+
+	@Test
+	public void homeWithHtml() throws Exception {
+		HttpHeaders headers = new HttpHeaders();
+		headers.setAccept(Arrays.asList(MediaType.TEXT_HTML));
+		ResponseEntity<String> response = new TestRestTemplate().exchange(
+				new RequestEntity<Void>(headers , HttpMethod.GET, new URI("http://localhost:"
+						+ port)), String.class);
+		assertTrue("Wrong body: " + response, response.getBody().contains("HAL Browser"));
+	}
+
+}

spring-boot-samples/spring-boot-sample-hypermedia/src/test/java/demo/SpringBootHypermediaApplicationTests.java

@@ -0,0 +1,18 @@
+package demo;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.web.WebAppConfiguration;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = SpringBootHypermediaApplication.class)
+@WebAppConfiguration
+public class SpringBootHypermediaApplicationTests {
+
+	@Test
+	public void contextLoads() {
+	}
+
+}