Improve EnumSet handling in MappingRedisConverter.

Add special handling of EnumSet, extracting the value type hint from the source to create the instance.

See: #3179

Author: christophstrobl

src/main/java/org/springframework/data/redis/core/convert/MappingRedisConverter.java

@@ -409,10 +409,15 @@ public void write(@Nullable Object source, RedisData sink) {
 			if (collection instanceof List) {
 				collectionTargetType = List.class;
 			} else if (collection instanceof Set) {
-				collectionTargetType = collection instanceof EnumSet ? EnumSet.class : Set.class;
+				if (collection instanceof EnumSet<?>) {
+					collectionTargetType = EnumSet.class;
+				} else {
+					collectionTargetType = Set.class;
+				}
 			}
+
 			typeMapper.writeType(collectionTargetType, sink.getBucket().getPath());
-			writeCollection(sink.getKeyspace(), "", collection, TypeInformation.of(Object.class), sink);
+			writeCollection(sink.getKeyspace(), "", collection, TypeInformation.OBJECT, sink);
 			return;
 		}
 
@@ -829,7 +834,13 @@ private void writeToBucket(String path, @Nullable Object value, RedisData sink,
 
 		boolean isArray = collectionType.isArray();
 		Class<?> collectionTypeToUse = isArray ? ArrayList.class : collectionType;
-		Collection<Object> target = CollectionFactory.createCollection(collectionTypeToUse, valueType, keys.size());
+		Class<?> valueTypeToUse = valueType;
+
+		if (collectionTypeToUse == EnumSet.class) {
+			valueTypeToUse = findFirstElementType(bucket, keys, valueType);
+		}
+
+		Collection<Object> target = CollectionFactory.createCollection(collectionTypeToUse, valueTypeToUse, keys.size());
 
 		for (String key : keys) {
 
@@ -977,6 +988,17 @@ private void writeMap(@Nullable String keyspace, String path, Class<?> mapValueT
 		return conversionService.convert(toBytes(mapKey), targetType);
 	}
 
+	private Class<?> findFirstElementType(Bucket bucket, List<String> keys, Class<?> fallbackType) {
+
+		Optional<String> firstElement = keys.stream().filter(typeMapper::isTypeKey)
+				.map(it -> it.substring(0, it.indexOf(']') + 1)).findFirst();
+		if (firstElement.isEmpty()) {
+			return fallbackType;
+		}
+
+		return getTypeHint(firstElement.get(), bucket, fallbackType);
+	}
+
 	private Class<?> getTypeHint(String path, Bucket bucket, Class<?> fallback) {
 
 		TypeInformation<?> typeInformation = typeMapper.readType(bucket.getPropertyPath(path),

src/test/java/org/springframework/data/redis/core/convert/MappingRedisConverterUnitTests.java

@@ -59,6 +59,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
+import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -2044,11 +2045,14 @@ void readsPlainCollectionIfObjectTypeRequested(Class<?> type, Collection<Object>
 
 		Object target = this.converter.read(Object.class, source.getRedisData());
 
-		assertThat(target).isInstanceOf(type).asInstanceOf(InstanceOfAssertFactories.COLLECTION).containsExactlyElementsOf(collection);
+		assertThat(target).isInstanceOf(type).asInstanceOf(InstanceOfAssertFactories.COLLECTION)
+				.containsExactlyElementsOf(collection);
 	}
 
 	private static Stream<Arguments> justCollections() {
-		return Stream.of(Arguments.of(List.class, Arrays.asList("Hello", "stream", "message", 100L)), Arguments.of(Set.class, Set.of("Hello", "stream", "message", 100L)));
+		return Stream.of(Arguments.of(List.class, Arrays.asList("Hello", "stream", "message", 100L)),
+				Arguments.of(Set.class, Set.of("Hello", "stream", "message", 100L)),
+				Arguments.of(EnumSet.class, EnumSet.allOf(Gender.class)));
 	}
 
 	private RedisTestData write(Object source) {