#841 - Added builder API to HalLinkRelation.

This allows more convenient setup of multiple HalLinkRelation instances for the same curie.

Additional unit tests.

src/main/java/org/springframework/hateoas/mediatype/hal/HalLinkRelation.java

@@ -105,6 +105,16 @@ public class HalLinkRelation implements LinkRelation, MessageSourceResolvable {
 		return new HalLinkRelation(null, rel);
 	}
 
+	/**
+	 * Creates a new {@link HalLinkRelationBuilder} for the given curie.
+	 *
+	 * @param curie must not be {@literal null} or empty.
+	 * @return will never be {@literal null}.
+	 */
+	public static HalLinkRelationBuilder curieBuilder(String curie) {
+		return relation -> new HalLinkRelation(curie, relation);
+	}
+
 	/**
 	 * Creates a new {@link HalLinkRelation} curied to the given value.
 	 *
@@ -162,6 +172,22 @@ public class HalLinkRelation implements LinkRelation, MessageSourceResolvable {
 				.toArray(String[]::new);
 	}
 
+	/**
+	 * Simple builder interface to easily create multiple {@link HalLinkRelation}s for a single curie.
+	 *
+	 * @author Oliver Drotbohm
+	 */
+	public interface HalLinkRelationBuilder {
+
+		/**
+		 * Creates a new {@link HalLinkRelation} based on the current curie settings.
+		 *
+		 * @param relation must not be {@literal null} or empty.
+		 * @return will never be {@literal null}.
+		 */
+		HalLinkRelation relation(String relation);
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Object#toString()

src/test/java/org/springframework/hateoas/mediatype/hal/HalLinkRelationUnitTest.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright 2019 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.mediatype.hal;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.Test;
+import org.springframework.hateoas.IanaLinkRelations;
+import org.springframework.hateoas.LinkRelation;
+import org.springframework.hateoas.mediatype.hal.HalLinkRelation.HalLinkRelationBuilder;
+
+/**
+ * Unit tests for {@link HalLinkRelation}.
+ *
+ * @author Oliver Drotbohm
+ */
+public class HalLinkRelationUnitTest {
+
+	@Test // #841
+	public void createsCuriedLinkRelation() {
+
+		HalLinkRelation relation = HalLinkRelation.curied("curie", "relation");
+
+		assertThat(relation.isCuried()).isTrue();
+		assertThat(relation.value()).isEqualTo("curie:relation");
+	}
+
+	@Test // #841
+	public void curieBuilderCreatesLinkRelations() {
+
+		HalLinkRelationBuilder builder = HalLinkRelation.curieBuilder("curie");
+
+		assertThat(builder.relation("relation").value()).isEqualTo("curie:relation");
+	}
+
+	@Test // #841
+	public void parsesCuriedLinkRelation() {
+
+		HalLinkRelation relation = HalLinkRelation.of(LinkRelation.of("already:curied"));
+
+		assertThat(relation.isCuried()).isTrue();
+		assertThat(relation.getLocalPart()).isEqualTo("curied");
+	}
+
+	@Test // #841
+	public void parsesUncuriedLinkRelation() {
+
+		HalLinkRelation relation = HalLinkRelation.of(LinkRelation.of("uncuried"));
+
+		assertThat(relation.isCuried()).isFalse();
+		assertThat(relation.getLocalPart()).isEqualTo("uncuried");
+	}
+
+	@Test // 841
+	public void returnsHalLinkRelationOnCreation() {
+
+		HalLinkRelation relation = HalLinkRelation.curied("curie", "relation");
+
+		assertThat(HalLinkRelation.of(relation)).isSameAs(relation);
+	}
+
+	@Test // 841
+	public void curiesLinkRelation() {
+
+		HalLinkRelation relation = HalLinkRelation.of(LinkRelation.of("relation"));
+
+		HalLinkRelation curiedRelation = relation.curie("curie");
+
+		assertThat(curiedRelation.isCuried()).isTrue();
+		assertThat(curiedRelation.curie("otherCurie")).isEqualTo(HalLinkRelation.curied("otherCurie", "relation"));
+	}
+
+	@Test // 841
+	public void skipsCurieIfAlreadyCuried() {
+
+		HalLinkRelation relation = HalLinkRelation.curied("curie", "relation");
+
+		assertThat(relation.curieIfUncuried("otherCurie")).isEqualTo(relation);
+	}
+
+	@Test // #841
+	public void skipsCurieForIanaLinkRelation() {
+
+		HalLinkRelation relation = HalLinkRelation.of(IanaLinkRelations.SELF).curieIfUncuried("curie");
+
+		assertThat(relation.isCuried()).isFalse();
+	}
+
+	@Test // #841
+	public void exposesValueAndLocalPartAsMessageCode() {
+
+		HalLinkRelation relation = HalLinkRelation.curied("curie", "relation");
+
+		assertThat(relation.getCodes()).containsExactly("_links.curie:relation.title", "_links.relation.title");
+	}
+}