GH-2333 - Fix custom media type registration in HalConfiguration.

With the addition of the vnd.hal+json media type, our registration of custom media types ordered these behind the legacy hal+json media type. We now try to find the first of the default media types and insert custom ones right before that one.

Author: odrotbohm

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

@@ -40,6 +40,7 @@
 public class HalConfiguration {
 
 	private static final PathMatcher MATCHER = new AntPathMatcher();
+	private static final List<MediaType> DEFAULT_MEDIA_TYPES = List.of(MediaTypes.HAL_JSON, MediaTypes.VND_HAL_JSON);
 
 	/**
 	 * Configures how to render links in case there is exactly one defined for a given link relation in general. By
@@ -67,8 +68,7 @@ public class HalConfiguration {
 	 */
 	public HalConfiguration() {
 
-		this(RenderSingleLinks.AS_SINGLE, new LinkedHashMap<>(), true, true, __ -> {},
-				List.of(MediaTypes.HAL_JSON, MediaTypes.VND_HAL_JSON));
+		this(RenderSingleLinks.AS_SINGLE, new LinkedHashMap<>(), true, true, __ -> {}, DEFAULT_MEDIA_TYPES);
 	}
 
 	private HalConfiguration(RenderSingleLinks renderSingleLinks, Map<String, RenderSingleLinks> singleLinksPerPattern,
@@ -233,8 +233,10 @@ public HalConfiguration withMediaType(MediaType mediaType) {
 			return this;
 		}
 
+		var index = mediaTypes.indexOf(DEFAULT_MEDIA_TYPES.get(0));
+
 		List<MediaType> newMediaTypes = new ArrayList<>(mediaTypes);
-		newMediaTypes.add(mediaTypes.size() - 1, mediaType);
+		newMediaTypes.add(index, mediaType);
 
 		return new HalConfiguration(renderSingleLinks, singleLinksPerPattern, applyPropertyNamingStrategy,
 				enforceEmbeddedCollections, objectMapperCustomizer, newMediaTypes);

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

@@ -19,7 +19,9 @@
 
 import org.junit.jupiter.api.Test;
 import org.springframework.hateoas.LinkRelation;
+import org.springframework.hateoas.MediaTypes;
 import org.springframework.hateoas.mediatype.hal.HalConfiguration.RenderSingleLinks;
+import org.springframework.http.MediaType;
 
 /**
  * Unit tests for {@link HalConfiguration}.
@@ -65,4 +67,18 @@ void registersWildcardedArrayLinksPatternForUri() {
 		assertThat(configuration.getSingleLinkRenderModeFor(LinkRelation.of("https://somehost/bar")))
 				.isEqualTo(RenderSingleLinks.AS_SINGLE);
 	}
+
+	@Test // GH-2333
+	void registersCustomMediaTypesFirst() {
+
+		var config = new HalConfiguration()
+				.withMediaType(MediaType.APPLICATION_CBOR)
+				.withMediaType(MediaType.APPLICATION_PDF);
+
+		assertThat(config.getMediaTypes()).containsExactly(
+				MediaType.APPLICATION_CBOR,
+				MediaType.APPLICATION_PDF,
+				MediaTypes.HAL_JSON,
+				MediaTypes.VND_HAL_JSON);
+	}
 }