#137 - Initial support for link templates.

Added LinkTemplate domain type that can deal with URI templates as defined in http://tools.ietf.org/html/rfc6570. We currently support /, ?, & and # variables up to level 3 of the spec (multiple parameter definitions). The templates can be expanded to a Link instance.

Added the necessary HAL mixins to render the instances as specified.

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

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2014 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;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A link template.
+ * 
+ * @author Oliver Gierke
+ */
+public class LinkTemplate extends Link {
+
+	private static final long serialVersionUID = 770560851448247262L;
+
+	private UriTemplate uriTemplate;
+
+	/**
+	 * Creates a new {@link LinkTemplate} for the given template string and relation type.
+	 * 
+	 * @param template must not be {@literal null} or empty.
+	 * @param rel must not be {@literal null} or empty.
+	 */
+	public LinkTemplate(String template, String rel) {
+
+		super(template, rel);
+
+		this.uriTemplate = new UriTemplate(template);
+	}
+
+	/**
+	 * Default constructor for the marshalling frameworks.
+	 */
+	protected LinkTemplate() {}
+
+	/**
+	 * Returns the variable names contained in the template.
+	 * 
+	 * @return
+	 */
+	public List<String> getVariableNames() {
+		return uriTemplate.getVariableNames();
+	}
+
+	/**
+	 * Returns whether the link is templated.
+	 * 
+	 * @return
+	 */
+	public boolean isTemplate() {
+		return true;
+	}
+
+	/**
+	 * Turns the current template into a {@link Link} by expanding it using the given parameters.
+	 * 
+	 * @param arguments
+	 * @return
+	 */
+	public Link toLink(Object... arguments) {
+		return new Link(uriTemplate.expand(arguments).toString(), getRel());
+	}
+
+	/**
+	 * Turns the current template into a {@link Link} by expanding it using the given parameters.
+	 * 
+	 * @param arguments
+	 * @return
+	 */
+	public Link toLink(Map<String, ? extends Object> arguments) {
+		return new Link(uriTemplate.expand(arguments).toString(), getRel());
+	}
+}