#1354 - Render Map entries once.

Maps, when wrapped inside an EntityModel, were getting double-rendered. Fix it so that they are only rendered once.

Original pull request: #1353.

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

@@ -21,6 +21,8 @@ import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.annotation.JsonProperty;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -118,7 +120,7 @@ public class EntityModel<T> extends RepresentationModel<EntityModel<T>> {
 	@JsonUnwrapped
 	@Nullable
 	public T getContent() {
-		return content;
+		return !Map.class.isInstance(content) ? content : null;
 	}
 
 	// Hacks to allow deserialization into an EntityModel<Map<String, Object>>
@@ -126,7 +128,7 @@ public class EntityModel<T> extends RepresentationModel<EntityModel<T>> {
 	@Nullable
 	@JsonAnyGetter
 	@SuppressWarnings("unchecked")
-	private Map<String, Object> getMapContent() {
+	public Map<String, Object> getMapContent() {
 		return Map.class.isInstance(content) ? (Map<String, Object>) content : null;
 	}
 

src/test/java/org/springframework/hateoas/mediatype/hal/Jackson2HalIntegrationTest.java

@@ -26,6 +26,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.TreeMap;
 import java.util.stream.Stream;
 
 import org.junit.jupiter.api.BeforeEach;
@@ -591,7 +592,8 @@ class Jackson2HalIntegrationTest {
 
 		EntityModel<Map<String, Object>> result = mapper.readValue(source, modelType);
 
-		assertThat(result.getContent()).containsEntry("key", "value");
+		assertThat(result.getContent()).isNull();
+		assertThat(result.getMapContent()).containsEntry("key", "value");
 	}
 
 	@Test // #1157
@@ -606,6 +608,22 @@ class Jackson2HalIntegrationTest {
 		assertThat(result.getContent().name).isEqualTo("Dave");
 	}
 
+	@Test // #1352
+	void rendersMapWithoutDuplicateEntries() throws JsonProcessingException {
+
+		Map<String, String> map = new TreeMap<>();
+		map.put("key", "value");
+		map.put("key2", "value2");
+
+		EntityModel<Map<String, String>> entityModel = EntityModel.of(map);
+		entityModel.add(Link.of("http://example.com"));
+
+		String serialized = mapper.writeValueAsString(entityModel);
+
+		assertThat(serialized)
+				.isEqualTo("{\"_links\":{\"self\":{\"href\":\"http://example.com\"}},\"key\":\"value\",\"key2\":\"value2\"}");
+	}
+
 	@Relation(collectionRelation = "someSample")
 	static class SomeSample {
 		@JsonProperty String name;

src/test/kotlin/org/springframework/hateoas/server/reactive/ReactiveRepresentationModelAssemblerBuilderDslUnitTest.kt

@@ -64,8 +64,10 @@ class ReactiveRepresentationModelAssemblerBuilderDslUnitTest : TestUtils() {
         runBlocking {
             val collectionModel = testResourceAssembler.toCollectionModelAndAwait(employees, exchange)
 
-            assertThat(collectionModel.content.flatMap { entityModel -> entityModel.links })
-                .containsExactlyInAnyOrder(Link.of("/employees", EMPLOYEES_RELATION), Link.of("/employees", EMPLOYEES_RELATION))
+            val extractLinks: (EntityModel<Employee>) -> Iterable<Link> = { entityModel -> entityModel.links }
+
+            assertThat(collectionModel.content.flatMap(extractLinks))
+                    .containsExactlyInAnyOrder(Link.of("/employees", EMPLOYEES_RELATION), Link.of("/employees", EMPLOYEES_RELATION))
         }
     }