From 79ebf9b5a49699cda5b141d8fb1e055794e4c62e Mon Sep 17 00:00:00 2001
From: Oliver Gierke <ogierke@pivotal.io>
Date: Wed, 29 Nov 2017 12:00:02 +0100
Subject: [PATCH] #671 - Polishing.
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Introduced Link.hasRel(…) and use that to filter link lookups in ResourceSupport.
---
 .../org/springframework/hateoas/Link.java     | 13 ++++++++++
 .../hateoas/ResourceSupport.java              |  4 ++--
 .../springframework/hateoas/LinkUnitTest.java | 24 +++++++++++++++++++
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/springframework/hateoas/Link.java b/src/main/java/org/springframework/hateoas/Link.java
index dde6fac6..388708b8 100755
--- a/src/main/java/org/springframework/hateoas/Link.java
+++ b/src/main/java/org/springframework/hateoas/Link.java
@@ -168,6 +168,19 @@ public class Link implements Serializable {
 		return new Link(getUriTemplate().expand(arguments).toString(), getRel());
 	}
 
+	/**
+	 * Returns whether the current {@link Link} has the given link relation.
+	 * 
+	 * @param rel must not be {@literal null} or empty.
+	 * @return
+	 */
+	public boolean hasRel(String rel) {
+
+		Assert.hasText(rel, "Link relation must not be null or empty!");
+
+		return this.rel.equals(rel);
+	}
+
 	private UriTemplate getUriTemplate() {
 
 		if (template == null) {
diff --git a/src/main/java/org/springframework/hateoas/ResourceSupport.java b/src/main/java/org/springframework/hateoas/ResourceSupport.java
index 22835a70..16c50cdc 100755
--- a/src/main/java/org/springframework/hateoas/ResourceSupport.java
+++ b/src/main/java/org/springframework/hateoas/ResourceSupport.java
@@ -126,7 +126,7 @@ public class ResourceSupport implements Identifiable<Link> {
 	public Optional<Link> getLink(String rel) {
 
 		return links.stream() //
-				.filter(link -> link.getRel().equals(rel)) //
+				.filter(link -> link.hasRel(rel)) //
 				.findFirst();
 	}
 
@@ -151,7 +151,7 @@ public class ResourceSupport implements Identifiable<Link> {
 	public List<Link> getLinks(String rel) {
 
 		return links.stream() //
-				.filter(link -> link.getRel().equals(rel)) //
+				.filter(link -> link.hasRel(rel)) //
 				.collect(Collectors.toList());
 	}
 
diff --git a/src/test/java/org/springframework/hateoas/LinkUnitTest.java b/src/test/java/org/springframework/hateoas/LinkUnitTest.java
index fdf37869..41df6b07 100755
--- a/src/test/java/org/springframework/hateoas/LinkUnitTest.java
+++ b/src/test/java/org/springframework/hateoas/LinkUnitTest.java
@@ -223,4 +223,28 @@ public class LinkUnitTest {
 		assertThat(Link.valueOf("<http://localhost>; rel=\"http://acme.com/rels/foo-bar\"").getRel()) //
 				.isEqualTo("http://acme.com/rels/foo-bar");
 	}
+
+	/**
+	 * @see #671
+	 */
+	@Test
+	public void exposesLinkRelation() {
+
+		Link link = new Link("/", "foo");
+
+		assertThat(link.hasRel("foo")).isTrue();
+		assertThat(link.hasRel("bar")).isFalse();
+	}
+
+	/**
+	 * @see #671
+	 */
+	@Test
+	public void rejectsInvalidRelationsOnHasRel() {
+
+		Link link = new Link("/");
+
+		assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> link.hasRel(null));
+		assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> link.hasRel(""));
+	}
 }