Introduced EntityLinks abstraction.

EntityLinks allow accessing LinkBuilders or even Link instance based on components exposing REST resources for a particular domain type. The core implementation is ControllerEntityLinks that assumes a particular URI structure so that it can derive the URIs to be asked for per domain type. The domain type managed will be inspected from the @ExposesResourceFor annotation on a controller class. We provide a factory bean to allow configuring instances of ControllerEntityLinks based on a mapping annotation and LinkBuilderFactory.

Added infrastructure to activate automatic discovery of EntityLinks implementations through @EnableEntityLinks. This will automatically register ControllerEntityLinks instances for Spring MVC controllers annotated with @ExposesResourceFor as well as JAX-RS resources if JAX-RS is on the classpath. The mechanism essentially registers a DelegatingEntityLinks instance leveraging the Spring Plugin PluginRegistry mechanism to delegate to the actual EntityLinks instance actually registered for the entity type. It will become the primary EntityLinks bean in the ApplicationContext so that they can be autowired into client components safely.

src/main/java/org/springframework/hateoas/mvc/BasicLinkBuilder.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2012 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.mvc;
+
+import org.springframework.hateoas.LinkBuilder;
+import org.springframework.hateoas.core.LinkBuilderSupport;
+import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
+import org.springframework.web.util.UriComponentsBuilder;
+
+/**
+ * Simples {@link LinkBuilder} implementation possible. Exposes a link to the current servlet mapping only.
+ * 
+ * @author Oliver Gierke
+ */
+public class BasicLinkBuilder extends LinkBuilderSupport<BasicLinkBuilder> {
+
+	/**
+	 * Creates a new {@link BasicLinkBuilder} using the given {@link UriComponentsBuilder}.
+	 * 
+	 * @param builder must not be {@literal null}.
+	 */
+	private BasicLinkBuilder(UriComponentsBuilder builder) {
+		super(builder);
+	}
+
+	/**
+	 * Creates a new {@link BasicLinkBuilder} to link to the current servlet mapping.
+	 * 
+	 * @return
+	 */
+	public static BasicLinkBuilder linkToCurrentMapping() {
+		return new BasicLinkBuilder(ServletUriComponentsBuilder.fromCurrentServletMapping());
+	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.hateoas.mvc.LinkBuilderSupport#createNewInstance(org.springframework.web.util.UriComponentsBuilder)
+	 */
+	@Override
+	protected BasicLinkBuilder createNewInstance(UriComponentsBuilder builder) {
+		return new BasicLinkBuilder(builder);
+	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.hateoas.mvc.LinkBuilderSupport#getThis()
+	 */
+	@Override
+	protected BasicLinkBuilder getThis() {
+		return this;
+	}
+}