#185 - Traverson can now get LinkDiscoverers configured.

Moved to a setter based configuration for both the RestOperations and LinkDiscoverers to be used.

Related pull request: #189.

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

@@ -93,7 +93,15 @@ class Rels {
 		 */
 		@Override
 		public Link findInResponse(String response, MediaType mediaType) {
-			return discoverers.getLinkDiscovererFor(mediaType).findLinkWithRel(rel, response);
+
+			LinkDiscoverer discoverer = discoverers.getLinkDiscovererFor(mediaType);
+
+			if (discoverer == null) {
+				throw new IllegalStateException(String.format("Did not find LinkDiscoverer supporting media type %s!",
+						mediaType));
+			}
+
+			return discoverer.findLinkWithRel(rel, response);
 		}
 	}
 

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

@@ -62,11 +62,19 @@ import com.jayway.jsonpath.JsonPath;
  */
 public class Traverson {
 
+	private static final LinkDiscoverers DEFAULT_LINK_DISCOVERERS;
+
+	static {
+		LinkDiscoverer discoverer = new HalLinkDiscoverer();
+		DEFAULT_LINK_DISCOVERERS = new LinkDiscoverers(OrderAwarePluginRegistry.create(Arrays.asList(discoverer)));
+	}
+
 	private final URI baseUri;
-	private final RestOperations operations;
-	private final LinkDiscoverers discoverers;
 	private final List<MediaType> mediaTypes;
 
+	private RestOperations operations;
+	private LinkDiscoverers discoverers;
+
 	/**
 	 * Creates a new {@link Traverson} interacting with the given base URI and using the given {@link MediaType}s to
 	 * interact with the service.
@@ -75,29 +83,15 @@ public class Traverson {
 	 * @param mediaType must not be {@literal null} or empty.
 	 */
 	public Traverson(URI baseUri, MediaType... mediaTypes) {
-		this(null, baseUri, mediaTypes);
-	}
-
-	/**
-	 * Creates a new {@link Traverson} with custom rest operations, interacting with the given base URI and using the
-	 * given {@link MediaType}s to interact with the service. The custom rest operations will be prepared with message
-	 * converters for the given media types.
-	 * 
-	 * @param operations allowing to customize the http requests with interceptors, client configurations etc.
-	 * @param baseUri must not be {@literal null}.
-	 * @param mediaType must not be {@literal null} or empty.
-	 */
-	public Traverson(RestOperations operations, URI baseUri, MediaType... mediaTypes) {
 
 		Assert.notNull(baseUri, "Base URI must not be null!");
 		Assert.notEmpty(mediaTypes, "At least one media type must be given!");
 
 		this.mediaTypes = Arrays.asList(mediaTypes);
 		this.baseUri = baseUri;
-		this.operations = operations == null ? createDefaultTemplate(this.mediaTypes) : operations;
+		this.discoverers = DEFAULT_LINK_DISCOVERERS;
 
-		LinkDiscoverer discoverer = new HalLinkDiscoverer();
-		this.discoverers = new LinkDiscoverers(OrderAwarePluginRegistry.create(Arrays.asList(discoverer)));
+		setRestOperations(createDefaultTemplate(this.mediaTypes));
 	}
 
 	private static final RestOperations createDefaultTemplate(List<MediaType> mediaTypes) {
@@ -134,6 +128,34 @@ public class Traverson {
 		return converter;
 	}
 
+	/**
+	 * Configures the {@link RestOperations} to use. If {@literal null} is provided a default {@link RestTemplate} will be
+	 * used.
+	 * 
+	 * @param operations
+	 * @return
+	 */
+	public Traverson setRestOperations(RestOperations operations) {
+
+		this.operations = operations == null ? createDefaultTemplate(mediaTypes) : operations;
+		return this;
+	}
+
+	/**
+	 * Sets the {@link LinkDiscoverers} to use. By default a single {@link HalLinkDiscoverer} is registered. If
+	 * {@literal null} is provided the default is reapplied.
+	 * 
+	 * @param discoverer can be {@literal null}.
+	 * @return
+	 */
+	public Traverson setLinkDiscoverers(List<? extends LinkDiscoverer> discoverer) {
+
+		this.discoverers = discoverers == null ? DEFAULT_LINK_DISCOVERERS : new LinkDiscoverers(
+				OrderAwarePluginRegistry.create(discoverer));
+
+		return this;
+	}
+
 	/**
 	 * Sets up a {@link TraversalBuilder} to follow the given rels.
 	 * 

src/test/java/org/springframework/hateoas/client/Server.java

@@ -30,6 +30,7 @@ import org.springframework.hateoas.Resource;
 import org.springframework.hateoas.Resources;
 import org.springframework.hateoas.core.EvoInflectorRelProvider;
 import org.springframework.hateoas.hal.Jackson2HalModule;
+import org.springframework.http.MediaType;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
@@ -66,6 +67,20 @@ public class Server implements Closeable {
 				havingPathEqualTo("/"). //
 				respond(). //
 				withBody("");
+
+		// For GitHubLinkDiscoverer tests
+
+		onRequest(). //
+				havingPathEqualTo("/github"). //
+				respond(). //
+				withBody("{ \"foo_url\" : \"" + rootResource() + "/github/4711\"}"). //
+				withContentType(MediaType.APPLICATION_JSON_VALUE);
+
+		onRequest(). //
+				havingPathEqualTo("/github/4711"). //
+				respond(). //
+				withBody("{ \"key\" : \"value\"}"). //
+				withContentType(MediaType.APPLICATION_JSON_VALUE);
 	}
 
 	public String rootResource() {

src/test/java/org/springframework/hateoas/client/TraversonTests.java

@@ -30,6 +30,7 @@ import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.MediaTypes;
 import org.springframework.hateoas.Resource;
+import org.springframework.hateoas.core.JsonPathLinkDiscoverer;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpRequest;
 import org.springframework.http.MediaType;
@@ -176,12 +177,26 @@ public class TraversonTests {
 		RestTemplate restTemplate = new RestTemplate();
 		restTemplate.setInterceptors(Arrays.<ClientHttpRequestInterceptor> asList(interceptor));
 
-		this.traverson = new Traverson(restTemplate, baseUri, MediaTypes.HAL_JSON);
+		this.traverson = new Traverson(baseUri, MediaTypes.HAL_JSON);
+		this.traverson.setRestOperations(restTemplate);
 
 		traverson.follow("movies", "movie", "actor").<String> toObject("$.name");
 		assertThat(interceptor.intercepted, is(4));
 	}
 
+	/**
+	 * @see #185
+	 */
+	@Test
+	public void usesCustomLinkDiscoverer() {
+
+		this.traverson = new Traverson(URI.create(server.rootResource() + "/github"), MediaType.APPLICATION_JSON);
+		this.traverson.setLinkDiscoverers(Arrays.asList(new GitHubLinkDiscoverer()));
+
+		String value = this.traverson.follow("foo").toObject("$.key");
+		assertThat(value, is("value"));
+	}
+
 	private void setUpActors() {
 
 		Resource<Actor> actor = new Resource<Actor>(new Actor("Keanu Reaves"));
@@ -206,4 +221,11 @@ public class TraversonTests {
 			return execution.execute(request, body);
 		}
 	};
+
+	static class GitHubLinkDiscoverer extends JsonPathLinkDiscoverer {
+
+		public GitHubLinkDiscoverer() {
+			super("$.%s_url", MediaType.APPLICATION_JSON);
+		}
+	}
 }