Consistent support for MultiValueMap and common Map implementations

Closes gh-30440

spring-core/src/main/java/org/springframework/core/CollectionFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -68,6 +68,7 @@ public final class CollectionFactory {
 		approximableCollectionTypes.add(SortedSet.class);
 		approximableCollectionTypes.add(NavigableSet.class);
 		approximableMapTypes.add(Map.class);
+		approximableMapTypes.add(MultiValueMap.class);
 		approximableMapTypes.add(SortedMap.class);
 		approximableMapTypes.add(NavigableMap.class);
 
@@ -80,6 +81,7 @@ public final class CollectionFactory {
 		approximableCollectionTypes.add(EnumSet.class);
 		approximableMapTypes.add(HashMap.class);
 		approximableMapTypes.add(LinkedHashMap.class);
+		approximableMapTypes.add(LinkedMultiValueMap.class);
 		approximableMapTypes.add(TreeMap.class);
 		approximableMapTypes.add(EnumMap.class);
 	}
@@ -121,13 +123,7 @@ public final class CollectionFactory {
 	 */
 	@SuppressWarnings({"rawtypes", "unchecked", "cast"})
 	public static <E> Collection<E> createApproximateCollection(@Nullable Object collection, int capacity) {
-		if (collection instanceof LinkedList) {
-			return new LinkedList<>();
-		}
-		else if (collection instanceof List) {
-			return new ArrayList<>(capacity);
-		}
-		else if (collection instanceof EnumSet) {
+		if (collection instanceof EnumSet) {
 			// Cast is necessary for compilation in Eclipse 4.4.1.
 			Collection<E> enumSet = (Collection<E>) EnumSet.copyOf((EnumSet) collection);
 			enumSet.clear();
@@ -136,6 +132,12 @@ public final class CollectionFactory {
 		else if (collection instanceof SortedSet) {
 			return new TreeSet<>(((SortedSet<E>) collection).comparator());
 		}
+		if (collection instanceof LinkedList) {
+			return new LinkedList<>();
+		}
+		else if (collection instanceof List) {
+			return new ArrayList<>(capacity);
+		}
 		else {
 			return new LinkedHashSet<>(capacity);
 		}
@@ -191,8 +193,8 @@ public final class CollectionFactory {
 		else if (LinkedList.class == collectionType) {
 			return new LinkedList<>();
 		}
-		else if (TreeSet.class == collectionType || NavigableSet.class == collectionType
-				|| SortedSet.class == collectionType) {
+		else if (TreeSet.class == collectionType || NavigableSet.class == collectionType ||
+				SortedSet.class == collectionType) {
 			return new TreeSet<>();
 		}
 		else if (EnumSet.class.isAssignableFrom(collectionType)) {
@@ -251,6 +253,9 @@ public final class CollectionFactory {
 		else if (map instanceof SortedMap) {
 			return new TreeMap<>(((SortedMap<K, V>) map).comparator());
 		}
+		else if (map instanceof MultiValueMap) {
+			return new LinkedMultiValueMap(capacity);
+		}
 		else {
 			return new LinkedHashMap<>(capacity);
 		}
@@ -297,26 +302,21 @@ public final class CollectionFactory {
 	@SuppressWarnings({"rawtypes", "unchecked"})
 	public static <K, V> Map<K, V> createMap(Class<?> mapType, @Nullable Class<?> keyType, int capacity) {
 		Assert.notNull(mapType, "Map type must not be null");
-		if (mapType.isInterface()) {
-			if (Map.class == mapType) {
-				return new LinkedHashMap<>(capacity);
-			}
-			else if (SortedMap.class == mapType || NavigableMap.class == mapType) {
-				return new TreeMap<>();
-			}
-			else if (MultiValueMap.class == mapType) {
-				return new LinkedMultiValueMap();
-			}
-			else {
-				throw new IllegalArgumentException("Unsupported Map interface: " + mapType.getName());
-			}
+		if (LinkedHashMap.class == mapType || HashMap.class == mapType || Map.class == mapType) {
+			return new LinkedHashMap<>(capacity);
+		}
+		else if (LinkedMultiValueMap.class == mapType || MultiValueMap.class == mapType) {
+			return new LinkedMultiValueMap();
+		}
+		else if (TreeMap.class == mapType || SortedMap.class == mapType || NavigableMap.class == mapType) {
+			return new TreeMap<>();
 		}
 		else if (EnumMap.class == mapType) {
 			Assert.notNull(keyType, "Cannot create EnumMap for unknown key type");
 			return new EnumMap(asEnumType(keyType));
 		}
 		else {
-			if (!Map.class.isAssignableFrom(mapType)) {
+			if (mapType.isInterface() || !Map.class.isAssignableFrom(mapType)) {
 				throw new IllegalArgumentException("Unsupported Map type: " + mapType.getName());
 			}
 			try {

spring-core/src/test/java/org/springframework/core/CollectionFactoryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -209,21 +209,23 @@ class CollectionFactoryTests {
 	@Test
 	void createsCollectionsCorrectly() {
 		// interfaces
-		assertThat(createCollection(List.class, 0)).isInstanceOf(ArrayList.class);
-		assertThat(createCollection(Set.class, 0)).isInstanceOf(LinkedHashSet.class);
-		assertThat(createCollection(Collection.class, 0)).isInstanceOf(LinkedHashSet.class);
-		assertThat(createCollection(SortedSet.class, 0)).isInstanceOf(TreeSet.class);
-		assertThat(createCollection(NavigableSet.class, 0)).isInstanceOf(TreeSet.class);
-
-		assertThat(createCollection(List.class, String.class, 0)).isInstanceOf(ArrayList.class);
-		assertThat(createCollection(Set.class, String.class, 0)).isInstanceOf(LinkedHashSet.class);
-		assertThat(createCollection(Collection.class, String.class, 0)).isInstanceOf(LinkedHashSet.class);
-		assertThat(createCollection(SortedSet.class, String.class, 0)).isInstanceOf(TreeSet.class);
-		assertThat(createCollection(NavigableSet.class, String.class, 0)).isInstanceOf(TreeSet.class);
+		testCollection(List.class, ArrayList.class);
+		testCollection(Set.class, LinkedHashSet.class);
+		testCollection(Collection.class, LinkedHashSet.class);
+		testCollection(SortedSet.class, TreeSet.class);
+		testCollection(NavigableSet.class, TreeSet.class);
 
 		// concrete types
-		assertThat(createCollection(HashSet.class, 0)).isInstanceOf(HashSet.class);
-		assertThat(createCollection(HashSet.class, String.class, 0)).isInstanceOf(HashSet.class);
+		testCollection(ArrayList.class, ArrayList.class);
+		testCollection(HashSet.class, LinkedHashSet.class);
+		testCollection(LinkedHashSet.class, LinkedHashSet.class);
+		testCollection(TreeSet.class, TreeSet.class);
+	}
+
+	private void testCollection(Class<?> collectionType, Class<?> resultType) {
+		assertThat(CollectionFactory.isApproximableCollectionType(collectionType)).isTrue();
+		assertThat(createCollection(collectionType, 0)).isInstanceOf(resultType);
+		assertThat(createCollection(collectionType, String.class, 0)).isInstanceOf(resultType);
 	}
 
 	@Test
@@ -258,20 +260,22 @@ class CollectionFactoryTests {
 	@Test
 	void createsMapsCorrectly() {
 		// interfaces
-		assertThat(createMap(Map.class, 0)).isInstanceOf(LinkedHashMap.class);
-		assertThat(createMap(SortedMap.class, 0)).isInstanceOf(TreeMap.class);
-		assertThat(createMap(NavigableMap.class, 0)).isInstanceOf(TreeMap.class);
-		assertThat(createMap(MultiValueMap.class, 0)).isInstanceOf(LinkedMultiValueMap.class);
-
-		assertThat(createMap(Map.class, String.class, 0)).isInstanceOf(LinkedHashMap.class);
-		assertThat(createMap(SortedMap.class, String.class, 0)).isInstanceOf(TreeMap.class);
-		assertThat(createMap(NavigableMap.class, String.class, 0)).isInstanceOf(TreeMap.class);
-		assertThat(createMap(MultiValueMap.class, String.class, 0)).isInstanceOf(LinkedMultiValueMap.class);
+		testMap(Map.class, LinkedHashMap.class);
+		testMap(SortedMap.class, TreeMap.class);
+		testMap(NavigableMap.class, TreeMap.class);
+		testMap(MultiValueMap.class, LinkedMultiValueMap.class);
 
 		// concrete types
-		assertThat(createMap(HashMap.class, 0)).isInstanceOf(HashMap.class);
+		testMap(HashMap.class, LinkedHashMap.class);
+		testMap(LinkedHashMap.class, LinkedHashMap.class);
+		testMap(TreeMap.class, TreeMap.class);
+		testMap(LinkedMultiValueMap.class, LinkedMultiValueMap.class);
+	}
 
-		assertThat(createMap(HashMap.class, String.class, 0)).isInstanceOf(HashMap.class);
+	private void testMap(Class<?> mapType, Class<?> resultType) {
+		assertThat(CollectionFactory.isApproximableMapType(mapType)).isTrue();
+		assertThat(createMap(mapType, 0)).isInstanceOf(resultType);
+		assertThat(createMap(mapType, String.class, 0)).isInstanceOf(resultType);
 	}
 
 	@Test